Book Review: A Gardener’s Guide to Botany

Avid gardeners spend a lot of time getting up close and personal with their plants. Whether they have a background in botany or not, they are bound to notice things about plants that others won’t. Questions are sure to arise about what their plants are up to, how they manage to do the things they do, or what might be done to help make their lives better. In the age of information, answers can be found at the touch of a button and from a wide variety of sources, some more trustworthy than others. The latest resource for gardeners with a question is A Gardener’s Guide to Botany. Written by plant expert and seasoned science communicator, Scott Zona, this is a source of information that’s not only trusted and highly credible, but also approachable for readers at any level and an absolute joy to read.

A Gardener’s Guide to Botany by Scott Zona, Ph.D.

You may know Zona as the go-to guy when it comes to questions about palms or tropical plants, but his knowledge of the plant kingdom extends far beyond these diverse groups. Zona has spent the majority of his life studying plants in all their forms across a wide variety of landscapes and has been sharing his knowledge through various institutions and societies that he’s been a part of along the way. His book is like a summary or overview of all the things he’s learned throughout this journey. It’s also just the beginning, a jumping off point and invitation to learn even more about the endlessly fascinating world of botany.

In the first chapter, Zona helps us understand just what makes a plant a plant – what separates plants from all other walks of life, and what plants have in common with other living things. Plants were one of the first forms of life that came about in the early years of life on our planet. Their evolution helped set the stage for so many other lifeforms to come. Due to the fact that they are generally fixed to one spot for the duration of their lives, they have had to adapt to deal with a wide variety of threats and stressors without the benefit of being able to run away or head for higher ground. As climates around them have changed and landscapes have shifted, so have they. All the while, plants have continued to be primary producers and ecosystem engineers, benefiting the lives of so many other living things, including humans, right up until this very day. Their existence is critical to the continuation of life on earth. Many of the ways that plants have been able to be so successful for so many millions of years are described in Zona’s book.

The second chapter of A Gardener’s Guide to Botany is a lesson in plant anatomy. Zona provides an overview of the inner and outer workings of roots, shoots, leaves, flowers, and fruits. Understanding basic plant anatomy can be important for maintaining a successful garden; it’s also just incredibly interesting in its own right. Plants are simple constructions, yet show up in such diverse forms. By modifying their limited parts, they are able to produce a wide variety of interesting features unique to each species. A branch becomes a thorn, a leaf becomes a spine, a root becomes a fleshy storage organ, an inflorescence becomes a tendril. This is just the beginning of the many surprises plants have up their sleeves.

The tendrils of grape vines (Vitis spp.) are modified, sterile inflorescences.

The next three chapters are all about what plants need to survive, namely water, light, and nutrients. Gardeners know that if any of these three things are out of whack, their plants are sure to suffer. Luckily, plants have some experience adapting a number of ways to get the things they need. Roots can search the soil for water and pockets of nutrients. Shoots move in search of light and can produce leaves that match the intensity or amount of sunlight (smaller and thicker in full sun, broader and thinner in the shade). Relationships can be made with microbes that live in the soil in order to gain access to resources, and even to help plants defend themselves (which is the subject of chapter six). Sometimes light is too intense for plants, and plants have developed features to deal with this such as waxes on their leaves, hairy or fuzzy leaf surfaces, or additional plant pigments that can act as sunscreen. Some of these features also help the plant retain water when temperatures are high. Other plant species have adaptations to live in water-abundant environments, such as drip tips on their leaves to help them shed water or special tissues in their stems and roots that help facilitate gas exchange.

Plants need light to carry out photosynthesis, so the more light the better. But not always. The newly emerging leaves of some species are red, orange, and/or yellow in color which helps protect the developing tissues from the intensity of the sun until the tissues have time to mature, at which point they turn their standard green color. In the fall, the leaves of deciduous plants experience a similar color change but in reverse. This change serves a similar function, protecting leaves from sun damage as they reabsorb nutrients back into the plant.

Lovage (Levisticum officinale) emerges in the spring, its leaves first taking on hues of purple and yellow which help protect the developing tissues from harsh, direct sunlight.

The chapter about defense is sure to be a popular one. Who doesn’t enjoy learning about the many ways these stationary organisms have developed to defend themselves against hordes of invaders out to destroy them? From fortifications like thorns, spines, and sticky hairs to any number of toxic substances produced within their tissues, many of which humans have learned to use for our own benefit. Some plants even recruit other species to help them out, like ants, mites, and various microbes. Of course, for all the defenses they put up, there are at least a few herbivorous creatures that manage to find a work around. And so the war continues.

In the following chapter, Zona covers another popular topic, plant sex. Pollinators and pollination have gained a lot of interest over the past decade or so, particularly among gardeners. Turning our gardens into habitats for bees and other insect pollinators is one way we can help conserve these important organisms. Understanding more about the specifics of pollination and plant reproduction will only help us improve these efforts. Learning about the many ways by which plants reproduce asexually also helps us out when we are trying to make more plants. Successful plant propagation and plant breeding rely on a good understanding of the concepts that Zona covers in chapter seven.

The bright yellow spots on the petals of snapdragons (Antirrhinum sp.) mimic pollen-loaded anthers and help draw in pollinators.

The final chapter is all about dispersal – how plants get around – and is one that I will be returning to repeatedly for some time. Plant dispersal is one of my favorite topics, and Zona does not disappoint. All the basic means of getting around are covered, and with them come dozens of stories that demand a curious mind look further into, like palm fruit dispersal by electric eels or the aardvarks that disperse the seeds of underground cucumbers. This a chapter that could have gone on for the whole book.

One of my favorite things about this book is that for the majority of the topics that Zona discusses, plant examples are given so that you can see for yourself, and many of those plants can be easily found either as a common garden plant or indoor houseplant. This means that you don’t have to travel the world to familiarize yourself with these concepts, instead you can see them in action right outside your door. Most of us, whether we have a garden or not, have easy access to plants, even if it’s just the weeds growing in the sidewalk cracks. This makes getting to know the Plant Kingdom a possibility for nearly anyone. As Zona writes, “a stroll in the garden or a hike through the woods is all it takes to begin a journey into a leafy, green world.” Let his book be “your passport, your interpreter, your currency converter, and your host on a learning adventure into the world of plants.”

More Book Reviews:

The Life Cycle of a Sunflower Stem Weevil

Last summer I came across a downy woodpecker hammering away at the stalk of a sunflower. I wondered what it was going after, and so I split open a stalk lengthwise to find the center of the stem hollowed out and several small larvae squirming through the debris left behind. A quick internet search later and I was learning about sunflower stem weevils, specifically Cylindrocopturus adspersus, which seems to be the species getting the most attention online and the stem-dwelling weevil that commercial sunflower growers seem most concerned about.

However, the range of sunflower stem weevil doesn’t appear to extend into Idaho, and so this is not likely to be the larvae I was seeing. There are other weevil species whose larvae can be found inside the stems of sunflowers (The sunflower I was observing was Helianthus annuus. I wasn’t specific about naming a particular species because it is my understanding that these weevils can be found on a variety of different Helianthus species., such as the cocklebur weevil (which is found in Idaho), but since larvae can be difficult to identify, I’ll wait to confirm the identity until I hear from an expert, find an adult weevil, and/or raise the larvae in captivity and see what it turns into. If and when that happens, I’ll be sure to update you. Until then, I present to you the life cycle of a sunflower stem weevil, which is still quite interesting, even if it’s not the species I found inside my sunflower stalks. And to be clear, the sunflower I observed was Helianthus annuus; however, the weevils I refer to in this post can be found on a number of different Helianthus species and related genera.

Sunflower stem weevils are in the family Curculionidae, which is the snout and bark beetle family. There are tens of thousands of species of weevils, a handful of which interact with sunflowers (plants in the genus Helianthus). Some weevil species eat the seeds, others eat the leaves, some are root feeders, while others are stem feeders. Depending on the life stage of a particular weevil species, it may consume multiple parts of a sunflower. Another interesting weevil is the sunflower headclipping weevil, which you can read about at The Prairie Ecologist.

Adult sunflower stem weevils are about 3/16 inch (4-5 mm) long and somewhat egg or oval shaped. They are grayish-brown with white spots. Their eyes, antennae, and snout are black, and their snout is short, curved, and held beneath the head. As adults, they can be found on sunflowers and sunflower relatives eating the leaves. However, they are not easily found. Their size, for one, makes them difficult to see, and they also move to the opposite sides of leaves and stems when disturbed, sometimes dropping to the ground as a threat approaches. You can see images of them on BugGuide.

unidentified larva in a sunflower stem

The larvae of sunflower stem weevils are about a quarter of a inch long and creamy white with a small, brown head capsule. They feed in the vascular tissue of sunflower stalks during the summer. In the fall, they migrate to the base of the stalks and create chambers in the woody tissue of the stalks and root crowns for overwintering.

Sunflower stem weevils have a single generation per year. After overwintering as larvae in the base of last year’s sunflowers, they pupate and emerge as adults in late spring or early summer. They find young sunflower plants and begin feeding on the leaves. After about 2-4 weeks, the weevils mate and lay eggs just beneath the epidermis of sunflower stems, usually in the stalk just below the cotyledon leaves. The eggs hatch a short time later and begin feeding in the stem until it’s time to overwinter.

the life cycle of a sunflower stem weevil

The damage caused by sunflower stem weevils is generally only a problem on sunflower farms, and only when weevils are found in high enough numbers to cause significant yield losses. Damage to leaves by the adults isn’t usually a concern. On the other hand, as the larvae tunnel through the stem, they can cause the plant to lodge (i.e. fall over prematurely), which is a problem particularly when the plants are machine harvested. Sunflower stem weevils can also introduce and help spread a fungus that causes black stem rot.

Read More About Sunflower Stem Weevil and Other Insect Pests of Sunflowers:

Eating Weeds: Cleavers Coffee

One of the world’s most beloved beverages comes from a species of plant found in the fourth largest family of flowering plants. Rubiaceae, also known as the coffee or bedstraw family, consists of around 13,500 species, placing it behind just Asteraceae, Orchidaceae, and Fabaceae for the most number of species. Coffea arabica, and other species in the genus Coffea, are grown for their fruits which are used to make coffee. This makes Rubiaceae one of the most economically important plant families. A family this size is bound to be home to a weed or two, and in fact, one of the most widespread and obnoxious weeds is also a member of Rubiaceae.

Galium aparine, known commonly by a slew of names including cleavers, occurs naturally across large portions of Europe, Asia, North Africa, and possibly even parts of North America. It has been introduced as a weed in many locations across North America, South America, Australia, New Zealand, Japan, and parts of Africa. It is of particular concern in agricultural settings where its lengthy, sprawling branches and sticky leaves get tangled up in harvesting equipment, while its tiny, prickly fruits get mixed in with seeds of similar size like canola.

Galium aparine

Sticky willy, as it is also known, is an annual plant that, in some cases, can have two generations per year – one in the spring (having germinated the previous fall) and one in the summer. Its stems are square, though not as sharply square as plants in the mint family, and can grow to around six feet long. They are weak, brittle, and don’t stand upright on their own; instead they are found scrambling across the ground or, when given the opportunity, climbing up the lengths of other plants in order to reach the sunlight. Leaves occur in whorls of six to eight and are simple and slender with entire margins. Flowers are produced at leaf axils along the lengths of the branches and are tiny, four-petaled, star-shaped, and greenish white. Fruits are borne in pairs and are round, single-seeded, indehiscent nutlets. The stems, leaves, and fruits are covered in stiff, hooked hairs or trichomes, earning it other names like catchweed bedstraw, grip grass, stickyweed, and velcro plant.

flowers and immature fruit on Galium aparine

Galium aparine is a climbing plant, but unlike other climbing plants, it doesn’t twine up things or produce structures like tendrils to hold itself up. Instead, its ability to climb is made possible by its abundant bristly hairs. A paper published in Proceedings of the Royal Society B (2011) investigates the way G. aparine climbs up other plants using the hairs on its leaves. A close inspection of the leaves reveals that the trichomes on the top of the leaf (the adaxial leaf surface) differ significantly from those found on the bottom of the leaf (the abaxial leaf surface). Adaxial trichomes curve towards the tip of the leaf, are hardened mainly at the tip, and are evenly distributed across the leaf surface. Abaxial trichomes curve towards the leaf base, are hardened throughout, and are found only on the midrib and leaf margins.

Having different types of hairs on their upper and lower leaf surfaces gives cleavers an advantage when it comes to climbing up neighboring plants. The authors of the paper describe the technique as a “ratchet mechanism.” When the upper surface of their leaf makes contact with the lower surface of another plant’s leaf, the flexible, outwardly hooked trichomes inhibit it from slipping further below the leaf and allow it to easily slide out from underneath it. When the lower surface of their leaf makes contact with the upper surface of another plant’s leaf, the stiff, inwardly hooked trichomes keep it attached to the leaf even if the other leaf starts to slip away and allows it to advance further across the leaf for better attachment and coverage. Using this ratchet mechanism, cleavers climb up the leaves of other plants, keeping their leaves above the other plant’s leaves, which gives them better access to sunlight. The basal stems of cleavers are highly flexible, which keeps them from breaking as the plant sways in the wind, tightly attached to their “host” plant.

fruits of Galium aparine

The hooked trichomes on the tiny fruits of cleavers readily attach to the fur and clothing of passing animals. The nutlets easily break free from the plants and can be transported long distances. They can also be harvested and made into a lightly caffeinated tea. Harvesting the fruit takes time and patience. I spent at least 20 minutes trying to harvest enough fruits for one small cup of cleavers coffee. The fruits don’t ripen evenly, and while I tried to pick mostly ripe fruits, I ended up with a selection of fruits in various stages of ripeness.

To make cleavers coffee, first toast the seeds for a few minutes in a pan heated to medium high, stirring them frequently. Next, grind them with a mortar and pestle and place the grinds in a strainer. Proceed as you would if you were making tea from loose leaf tea.

The toasted fruits and resulting tea should smell similar to coffee. The smell must not be strong, because my poor sense of smell didn’t really pick up on it. The taste is coffee-like, but I thought it was more similar to black tea. Sierra tried it and called it “a tea version of coffee.” If the fruits were easier to collect, I could see myself making this more often, but who has the time?

The leaves and stems of Galium aparine are also edible, and the plant is said to be a particular favorite of geese and chickens, bringing about yet another common name, goosegrass. In the book Weeds, Gareth Richards discusses the plant’s edibility: “It’s edible for humans but not that pleasant to eat; most culinary and medicinal uses center around infusing the plant in liquids.” Cooking with the leaves or turning them into some sort of spring tonic is something I’ll consider for a future post about eating cleavers.

More Eating Weeds Posts on Awkward Botany

Randomly Selected Botanical Terms: Glochids

The spines of a cactus are an obvious threat. They are generally sharp, smooth, and stiff; as soon as you are stabbed by one, it is immediately clear that you’ve gotten too close. Sitting at the base of the spines – or in place of spines – on many species of cacti is a less obvious, but significantly more heinous threat. Unless you’re looking closely, this hazard is practically invisible, and the pain and irritation that can come as a result of close contact has the potential to last significantly longer than the sharp poke of a spine. This nefarious plant part is called a glochid, and if you’ve ever made contact with one (or more likely several dozen of them), it’s not something you will soon forget.

Opuntia polyacantha x utahensis

The spine of a cactus is actually a leaf. The area from which a spine emerges from the fleshy, photosynthetic stem of a cactus is called an areole, which is equivalent to a node or bud on a more typical stem or branch from which leaves emerge. In place of typical looking leaves, a cactus produces spines and glochids. Like spines, glochids are also modified leaves, although they appear more like soft, little tufts of hair. However, this unassuming little tuft is not to be trifled with.

Close inspection of a glochid (with the help of a microscope) reveals why you don’t want them anywhere near your skin. While the surface of a cactus spine is often smooth and free of barbs, glochids are covered in backwards-facing barbs. The miniscule size of glochids combined with their pliable nature and retrose barbs, make it easy for them to work their way into your skin and stay there. Unlike spines, glochids easily detach from a cactus stem. Barely brushing up against a glochid-bearing cactus can result in getting stuck with several of them.

Opuntia basilaris var. heilii

Because glochids can be so fine and difficult to see, you may not even be aware they are there. You probably won’t even feel them at first. Removing them is a challenge thanks to their barbs, and since you may not be able to remove them all, the glochids that remain in your skin can continue to cause irritation for days, weeks, or even months after contact. For this reason, cactuses are generally best seen and not touched, or at the very least, handled with extreme care.

Apart from being a good form of defense, the glochids of some cactus species can serve an additional function. Most cactus species occur in arid or semi-arid climates, where access to water can be quite limited. In order to increase their chances of getting the water they need, some desert plants are able to collect water from the air. A few species of cactus do this, and glochids are a critical component in making this happen.

Cylindropuntia whipplei

A study published in the Journal of King Saud University – Science (2020) examined the dew harvesting ability of Opuntia stricta, commonly known as erect prickly pear. As described above, the spines of O. stricta are smooth, while the glochids are covered in retrose barbs. Both structures are waterproof due to hardened cell walls and cuticles. However, due in part to the conical shapes of both the glochids and their barbs, water droplets from the air are able to collect on the tips of the glochids. From there, the researchers observed the droplets in their travel towards the base of the glochids. As they moved downward, small droplets combined to form larger droplets.

At the base of the glochids are a series of trichomes, which are small hair-like outgrowths of the epidermis. The trichomes do not repel water, but rather are able to absorb the droplets as they reach the base of the glochids. For a plant species that receives very little water from the soil, being able to harvest dew from the air is critical for its survival, and this is thanks in part to those otherwise obnoxious glochids.

See Also: Prickles

Flowers Strips Bring All the Pollinators to the Yard

The longer I garden the more I gravitate towards creating habitats for creatures that rely on plants for survival. I’ve always been more interested in functional gardens rather than gardens that are simply “plants as furniture” (as Sierra likes to say) – a manicured, weed-free lawn, a few shrubs shaped into gumdrops, sterile flowers for color – and that interest has grown into a way of life. A garden should be more than just something nice to look at, and for those of us who’ve embraced the “messy ecosystems” approach, what’s considered “nice to look at” has shifted dramatically.

Thankfully, I’m not alone in this thinking. Gardens focused on pollinators, birds, habitats, native plants, etc. seem to be gaining in popularity. The question is, is it making a difference? At least one study, referred to below, seems to suggest that it is. And as more gardens like these are planted and more studies like this are done, perhaps we will get a clearer picture of their impact.

In 2017, eight 1000 square meter flower strips were planted in Munich, Germany. The sites had previously been lawn or “roadside greenery,” according to the report published in the Journal of Hymenoptera Research (2020). An additional flower strip, planted in 2015, was included in the study. Over the next year, an inventory of the number of bee species found in these nine flower strips was taken and compared both to the number of bee species that had been recorded in Munich since 1795 (324 species) and the number of bee species recorded in the 20 years prior to the planting of the flower strips (232 species).

In just a year’s time, these newly planted flower strips quickly attracted a surprising number of bees. The researchers identified 68 different species (which is 21% and 29% of the two categories of previously recorded species). As they had expected, most of the bees they identified were common, non-threatened, generalist species; however, they were surprised to also find several species that specialize on pollen from specific groups of plants. Future studies are needed to determine whether or not such flower strips help increase the populations of pollinators in the city, but it seems clear that they are a simple way to increase the amount of food for pollinators, if nothing else.

But perhaps these results shouldn’t be that surprising. Urban areas are not necessarily the biodiversity wastelands that the term “concrete jungle” seems to imply. Though fragmented and not always ideal, plenty of wildlife habitat can be found within a city. In his book, Pollinators and Pollination, Jeff Ollerton lists a number of studies that have been carried out in cities across the world documenting an impressive number of pollinating insects living within their borders [see this report in Conservation Biology (2017), for example]. As Ollerton writes, these studies “show that urbanization does not mean the total loss of pollinator diversity, and may in fact enhance it.” After all, “many of us city dwellers see every day, nature finds a home, a habitat, a place to thrive, wherever it will.”

In a chapter entitled, “The Significance of Gardens,” Ollerton continues to explore the ways in which cities can host a wide variety of flower visiting insects and birds. “Planted patches” don’t necessarily need to be managed as pollinator gardens in order to provide resources for these creatures, nor do all of the plants need to be native to the region to be effective. Rather, diversity in flower structure and timing seems to be key; “floral diversity always correlates with pollinator diversity regardless of the origin of the plants,” Ollerton writes in reference to pollination studies performed in British cities. The more “planted patches,” the better, as “a large and continuous floral display in gardens is the only way to maximize pollinator abundance and diversity.” Add to that, “if you allow some areas to become unmanaged, provide other suitable nesting sites or areas for food plants, and other resources that they need, a thriving oasis for pollinators can be created in any plot.”

ground nesting bee emerging from burrow

Bees and other pollinating insects are finding ways to live within our cities. There is no need to go to the lengths that I like to go in order to help them out. Simply adding a few more flowering plants to your yard, balcony, or patio can do the trick. Eliminating or limiting the use of pesticides and creating spaces for nesting sites are among other things you can do. Learning about specific pollinators and their needs doesn’t hurt either. The continued existence of these creatures is critical to life on earth, and this is one important issue where even simple actions can make a real difference.


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Awkward Botany on Outdoor Idaho (plus Send Us Your Questions)

I spend a lot time on this blog putting weeds in the spotlight, celebrating them for their successes and the unique and interesting plants they are. It’s rare that I get to share these sentiments outside of this particular venue, but I was given such an opportunity recently when asked to talk about weeds for an episode of Outdoor Idaho, a long running show on Idaho Public Television that covers Idaho’s natural history. The theme of this particular episode is wildflowers, so I was intrigued by the idea of coming on to discuss urban weeds. For many, the term “wildflowers” may invoke native plants blooming in natural areas in places far removed from the hustle and bustle of the city. But a wildflower doesn’t have to be a native plant, nor does it have to be growing in the wild. Any plant occurring naturally on its own without the assistance of humans can be a wildflower, and that includes our wild urban flora. I appreciated the chance to share this particular thought with the viewers of Outdoor Idaho.

photo credit: Jay Krajic

Along with me waxing on about weeds, the Wildflowers episode features a host of other Idahoans sharing their thoughts, expertise, and experiences with wildflowers. The episode is brief – coming in at under 30 minutes – but the producers packed in a ton of great wildflower content, and overall I found it to be an excellent representation of the flora of Idaho and a convincing argument for why we should appreciate and elevate these plants. The flora of any region is special and important in its own right, and Idaho’s flora is no different, including its weeds.

Check out Outdoor Idaho’s Wildfowers episode here.

In other news…

If you want to see more of me on the screen (and I’m not sure why you would), Sierra (a.k.a. Idaho Plant Doctor) and I are doing monthly Q&A videos in which we answer your questions about plants, gardening, pests and diseases, insects, or any other topic you might be curious about. You can tune in to those discussions on Sierra’s instagram. If you have questions of your own that you would like us to address, please leave them in the comments section below, or send them to me via the contact page or my instagram.

Weeds of Boise: Vacant Lot on West Kootenai Street

Every urban area is bound to have its share of vacant lots. These are sites that for whatever reason have been left undeveloped or were at one point developed but whose structures have since been removed. The maintenance on these lots can vary depending on who has ownership of them. Some are regularly mowed and/or treated with herbicide, while others go untouched for long periods of time. Even when there is some weed management occurring, vacant lots are locations where the urban wild flora dominates. Typically no one is coming in and removing weeds in an effort to cultivate something else, and so weeds run the show.

As with any piece of land populated by a diverse suite of wild plants, vacant lots are dynamic ecosystems, which you can read all about in the book Natural History of Vacant Lots by Matthew Vessel and Herbert Wong. The impact of humans can be seen in pretty much any ecosystem, but there are few places where that impact is more apparent than in a vacant lot. In lots located in bustling urban centers, human activity is constant. As Vessel and Wong write, “numerous ecosystem interactions are affected when humans intervene by spraying herbicides or insecticides, by trampling, by physically altering the area, or by depositing garbage and waste products.” These activities “can abruptly alter the availability and types of small habitats; this will in turn affect animal as well as plant diversity and population dynamics.” The dynamic nature of these sites is a reason why vacant lots are excellent places to familiarize yourself with the wild urban flora.

Kōura relaxing in a vacant lot

On our morning walks, Kōura and I have been visiting a small vacant lot on West Kootenai Street. We have watched as early spring weeds have come and gone, summer weeds have sprouted and taken off, perennial weeds have woken up for the year, and grass (much of which appears to have been intentionally planted) has grown tall and then been mowed with some regularity. Someone besides us is looking after this vacant lot, and it’s interesting to see how the plant community is responding. As Vessel and Wong note, “attempts to control weedy plants by mowing, cultivating, or spraying often initiate the beginning of a new cycle of growth.” For plants that are adapted to regular disturbance, measly attempts by humans to keep them in check are only minor setbacks in their path to ultimate dominance.

What follows are a few photos of some of the plants we’ve seen at the vacant lot on Kootenai Street, as well as an inventory of what can be found there. This list is not exhaustive and, as with other Weeds of Boise posts, will continue to be updated as I identify more species at this location.

dandelion (Taraxacum officinale)
grape hyacinth (Muscari armeniacum)
henbit (Lamium amplexicaule)
wild barley (Hordeum murinum) backed by cheatgrass (Bromus tectorum)
narrowleaf plantain (Plantago lanceolata) and broadleaf plantain (Plantago major)
perrennial sweet pea (Lathyrus latifolius) surrounded by redstem filaree (Erodium cicutarium)
whitetop (Lepidium sp.)
white clover (Trifolium repens)
  • Bromus tectorum (cheatgrass)
  • Capsella bursa-pastoris (shepherd’s purse)
  • Ceratocephala testiculata (bur buttercup)
  • Convolvulus arvensis (field bindweed)
  • Descurainia sophia (flixweed)
  • Draba verna (spring draba)
  • Erodium cicutarium (redstem filaree)
  • Geum urbanum (wood avens)
  • Holosteum umbellatum (jagged chickweed)
  • Hordeum murinum (wild barley)
  • Lactuca serriola (prickly lettuce)
  • Lamium amplexicaule (henbit)
  • Lathyrus latifolius (perennial sweet pea)
  • Lepidium sp. (whitetop)
  • Malva neglecta (dwarf mallow)
  • Medicago lupulina (black medic)
  • Muscari armeniacum (grape hyacinth)
  • Plantago lanceolata (narrowleaf plantain)
  • Plantago major (broadleaf plantain)
  • Poa bulbosa (bulbous bluegrass)
  • Poa pratensis (Kentucky bluegrass)
  • Rumex crispus (curly dock)
  • Taraxacum officinale (dandelion)
  • Tragopogon dubius (salsify)
  • Trifolium repens (white clover)
  • Veronica sp. (speedwell)

If you live in an urban area, chances are good there is a vacant lot near you. What have you found growing in your neighborhood vacant lot? Feel free to share in the comment section below.

In Praise of Vagabond Plants – A Book Review

A weed is a highly successful plant that shares a close relationship with humans. In many instances, weeds are seen as nuisance plants, interfering with the goals and intentions we have for a piece of land. In natural areas, they are blamed for, among other things, threatening the existence of the native flora, despite the fact that human activity and disturbance brought them there in the first place and continued human disturbance helps keep them there. In some instances, such as a vacant lot in an urban area, they pose no threat and their existence causes little if any harm, yet they are disparaged for being unsightly, hazardous, and out of place. Nevermind the fact that they are offering a number of ecosystem services free of charge.

For all these reasons and more, weeds get called some pretty nasty things and are the recipient of an unduly amount of ire. The extent that some of us will go to vilify a plant is a bit disturbing to me, so it’s always refreshing to come across a more reasonable approach to weeds. That tempered take is what I found in Gareth Richards’ book, Weeds: The Beauty and Uses of 50 Vagabond Plants, a production of the Royal Horticultural Society and whose vast archives were used to beautifully illustrate the book.

There seems to be a growing trend in the U.K. and other parts of Europe to be more accepting of weeds, to see them as part of our urban, suburban, and exurban flora, and to focus on the value they may bring rather than constantly reviling them as interlopers and thus trying to blast them out of existence with chemical warfare. (See also Wild About Weeds by Jack Wallington). I hope this is true, and I hope the trend continues and catches on in other parts of the world. As Richards writes, “Often the only crime a plant has committed is growing too well.” Thankfully, books like this help bring awareness to these highly fecund and robust plants and their many redeeming qualities.

Richards’ book starts out with a brief introduction and then proceeds with short profiles of 50+ different plant species that are commonly considered weeds. The focus of the book is on weeds found in the U.K.; however, weeds being what they are, at least a few (if not most) of the plants covered are bound to be growing near you regardless of where you live in the world. While there is some discussion of the invasive nature of a few of the plants profiled and the illegality of growing or transporting them – see Japanese knotweed, Himalayan balsam, and pontic rhododendron for example – the focus is not on management nor control. Instead, the discussion revolves around interesting aspects of the plants that makes them worth getting to know rather than something to simply eliminate.

As is often the case when discussing specific plants, medicinal uses and edibility feature heavily in Richards’ plant profiles. It’s interesting to learn about the many ways that humans have thought about and used plants historically, and some of the ways they were historically used are certainly still relevant today; however, many medicinal claims don’t stand the test of time nor do they have empirical evidence to back them up. For this reason, I generally take medicinal uses of plants with a grain of a salt and a healthy dose of skepticism. Edibility, on the other hand, has always been interesting to me, and just when I thought I had heard all the ways that dandelions can be eaten, Richards introduces me to another: “You can even harvest the flower buds for pickling; they make a useful homegrown caper substitute.”

What follows are a few excerpts from the book with accompanying photos of the plants in question.

Ground elder (Aegopodium podagraria) was originally introduced to gardens for its medicinal and edible qualities, but its aggressive behavior can be frustrating. Richards notes, “A useful plant for brave gardeners!”
The rhizomatous nature of yarrow (Achillea millefolium) makes it an excellent addition or alternative to turf grass, and thanks to its drought-tolerance, Richards asserts, “certainly lawns containing yarrow stay greener for longer in dry spells.
Speaking of lawns, “Creeping buttercup (Ranunculus repens) in your lawn is generally a sign that it’s too wet for short grass to thrive.” Richards recommends letting it become a meadow instead. “Sometimes the most rewarding way of gardening is to let nature do it for you.”
Regarding teasel (Dipsacus spp.), Richards writes: “It’s not only bees that adore them; when the seeds ripen they’re loved by birds, especially goldfinches. Try planting some in your garden as a homegrown alternative food source to replace shop-bought nyjer seed.” (photo credit: Sierra Laverty)
“Cats and dogs seek out couch grass (Elymus repens) when they want to chew on something – either for its minerals or to help them vomit to clear their stomachs, often of furballs.” Kōura can frequently be found chewing on it.
“Like many weeds, herb bennet (Geum urbanum) has some clever adaptations. Its nondescript leaves blend seamlessly with other plants, never drawing attention to themselves. And those [clove-scented] roots are really tough, making plants physically difficult to pull up by hand. … The seeds have small hooks and readily attach themselves to fur and clothing to hitch a free ride to pastures new.”

Regardless of how you feel about weeds, if you’re interested in plants at all, this book is worth getting your hands on and these plants are worth getting to know. They may not be the plants you prefer to see growing on your property, but they have interesting stories to tell and, in many cases, may not be as big of a problem as you originally thought. In discussing Spanish bluebells (Hyacinthoides hispanica) and its weedy relatives, Richards hits on a point that for me is one of the main takeaways of this book: “In an age where gardens are becoming wilder and the countryside ever more fragmented, and nature is on the march due to climate change, perhaps we should just learn to treasure the wild plants that thrive in the the new conditions we have made – wherever they originally came from.”

More Weeds Themed Book and Zine Reviews:

Dispersal by Open Sesame!

In certain instances, “open sesame” might be something you exclaim to magically open the door to a cave full of treasure, but for the sesame plant, open sesame is a way of life. In sesame’s case, seeds are the treasure, which are kept inside a four-chambered capsule. In order for the next generation of plants to have a chance at life, the seeds must be set free. Sesame’s story is similar to the stories of numerous other plant species whose seeds are born in dehiscent fruits. But in this instance, the process of opening those fruits is fairly unique.

Sesamum indicum is a domesticated plant with a 5000 plus year history of cultivation. It shares a genus with about 20 other species – most of which occur in sub-Saharan Africa – and belongs to the family Pedaliaceae – the sesame family. Sesame was first domesticated in India and is now grown in many other parts of the world. It is an annual plant that is drought and heat-tolerant and can be grown in poor soils and locations where many other crops might struggle. However, the best yields are achieved on farms with fertile soils and adequate moisture.

image credit: wikimedia commons

Depending on the variety and growing conditions, sesame can reach up to 5 feet tall and can be unbranched or highly branched. Its broad lance-shaped leaves are generally arranged directly across from each other on the stem. The flowers are tubular, similar in appearance to foxglove, and are typically self-pollinated and short-lived. They come in shades of white, pink, blue, and purple and continue to open throughout the growing season as the plant grows taller, even as fruits formed earlier mature. The fruits are deeply-grooved capsules with at least four separate chambers called locules. Rows of tiny, flat, teardrop shaped seeds are produced in each chamber. The seeds are prized for their high oil content and are also used in numerous other ways, both processed and fresh. One of my favorite uses for sesame seeds is tahini, which is one of the main ingredients in hummus.

The fruits of sesame are dehiscent, which means they naturally split open upon reaching maturity. Compare this to indehiscent fruits like acorns, which must either rot or be chewed open by an animal in order to free the seeds. Dehiscence is also called shattering, and in many domesticated crop plants, shattering is something that humans have selected against. If fruits dehisce before they can be harvested, seeds fall to the ground and are lost. Selecting varieties that hold on to their seed long enough to be harvested was imperative for crops like beans, peas, and grains. In domesticated sesame, the shattering trait persists and yield losses are often high.

Most of the world’s sesame crop is harvested by hand. The plants are cut, tied into bundles, and left to dry. Once dry, they are held upside down and beaten in order to collect the seeds from their dehisced capsules. When harvested this way, naturally shattering capsules may be preferred. But in places like the United States and Australia, where mechanical harvesting is desired, it has been necessary to develop new, indehiscent varieties that can be harvested using a combine without losing all the seed in the process. Developing varieties with shatter-resistant seed pods, has been challenging. In early trials, seed pods were too tough and passed through threshers without opening. Additional threshing damaged the seeds and caused the harvest to go rancid. Mechanically harvested varieties of sesame exist today, and improvements in these non-shattering varieties continue to be made.

In order to develop these new varieties, breeders have had to gain an understanding of the mechanisms behind dehiscence and the genes involved in this process. This research has helped us appreciate the unique way that the capsules of the sesame plant dehisce. As in the seed bearing parts of many other plant species, the capsules of sesame exhibit hygroscopic movements. That is, their movements are driven by changes in humidity. The simplest form of hygroscopic movement is bending, which can be seen in the opening and closing of pine cone scales. A more complex movement can be seen in the seed pods of many species in the pea family, which both bend and twist as they split open. In both of these examples, water is evaporating from the plant part in question. As it dries it bends and/or twists, thereby releasing its contents.

dehisced capsules of sesame (Sesamum indicum); photo credit: wikimedia commons (Dinesh Valke)

The cylindrical nature and cellular composition of sesame fruits leads to an even more complex form of hygroscopic movement. Initially, the capsule splits at the top, creating an opening to each of the four locules. The walls of each locule bend outward, then split and twist as the seed falls from the capsule. In a study published in Frontiers in Plant Science (2016), researchers found that differences in the capsule’s inner endocarp layer and outer mesocarp layer are what help lead to this interesting movement. The endocarp layer is composed of both transvere (i.e. circumferential) and longitudinal fiber cells, while the mesocarp is made up of soft parenchyma cells. The thicknesses of these two layers gradually changes along the length of the capsule. As the mesocarp dries, the capsule initially splits open and starts bending outwards, but as it does, resistance from the fiber cells in the endocarp layer causes further bending and twisting (see Figure 1 in the report for an illustration). As the researchers write, “the non-uniform relative thickness of the layers promotes a graded bi-axial bending, leading to the complex capsule opening movement.”

All this considered, a rock rolling away from the entrance of a cave after giving the command, “Open sesame!” almost seems simpler than the “open sesame” experienced by the fruit of the sesame plant.

See Also: Seed Shattering Lost – The Story of Foxtail Millet

The Wonderful World of Plantlets, Bulbils, Cormlets, Tubercles, and Gemmae

Probably the most well known strategy that plants have for dispersal is by way of seeds. Seeds are plants in embryo, and new generations of plants are born when seeds, released from their parent plants, find suitable locations to germinate. But one of the most amazing things about plants in general is that they have the ability to reproduce in a variety of different ways, and many plant species are not limited to seeds as their only means of dispersal. A paper by Scott Zona and Cody Coyotee Howard, published in Flora (February 2022), introduces us to the intriguing world of aerial vegetative diaspores – just one of the many ways that plants have to get around.

A diaspore is a plant structure that facilitates dispersal. Seeds are diaspores, as are spores, which are produced by non-seed bearing plants like mosses and ferns. If you’ve ever planted bulbs, you’ve handled another type of diaspore. Bulbs and corms, which many spring flowering plants are grown from, form little offshoots called bulblets and cormels that, when detached from their parent structure, can grow into new individuals. These vegetative diaspores are produced below ground. Aerial vegetative diaspores, on the other hand, are formed on above ground plant parts. This clunky term encompasses a number of different structures that are often simply called bulbils, which Zona and Howard explain is used as “a catch-all term that obscures their morphological identity.”

Compiling a list of plant species that feature aerial vegetative diaspores is a difficult task when plant descriptions from various sources use a broad selection of terminology for the same or similar plant parts. To help complete this task, Zona and Howard defined five distinct types of aerial vegetative diaspores – plantlets, bulbils, cormlets, tubercles, and gemmae – and came up with a list of 252 taxa that are known to feature at least one of these structures.

plantlets on the leaf margin of Kalanchoe daigremontiana (wikimedia commons; Aurélien Mora)

Plantlets are miniature plants attached to another plant. Once mature, they have clearly visible leaves, stems, and roots (or root initials) and are non-dormant, meaning they are ready to grow on their own as soon as they’re given the opportunity. The tiny plants borne along the margins of the leaves of mother of thousands (Kalanchoe daigremontiana) is a great example of a plantlet.

A bulbil consists of a shortened stem surrounded by scale leaves modified for food and water storage. Sometimes root initials are visible at the base of the bulbil. Bulbils remain dormant until they are dispersed and conditions are suitable for growth. When bulbils start growing but remain attached to the plant, they become a plantlet. A good example of a bulbil can be found on bulbous bluegrass (Poa bulbosa).

Cormlets are comprised of stem tissue and, like plantlets and bulbils, have a single axis of polarity. They have highly reduced scale leaves and are dormant at dispersal. Bulbil bugle lily (Watsonia meriana), despite its misleading common name, is a good example of a plant that produces cormlets.

Tubercles are made up of swollen stem tissue and, like tubers (their underground counterparts), have multiple shoot buds and multiple axes of polarity (meaning there is no right side up like there is in plantlets, bulbils, and cormlets). They lack scale leaves and are dormant at dispersal. Air potato (Dioscorea bulbifera) is an example of a tubercle-producing plant. As you might guess from the common name, potato-like structures are produced aerially on this vining plant that was introduced to North America from Africa and is now invasive in Florida.

A gemma is a tiny cluster of undifferentiated cells. Gemmae are non-dormant and lack polarity. They are the smallest and least common form of aerial vegetative diaspore and can be found on Drosera pygmaea, a species of sundew native to parts of Australia and New Zealand.

Drosera pygmaea (wikimedia commons; Björn S…)

Zona and Howard’s list of plants with aerial vegetative diaspores is the most comprehensive list to date – although it is undoubtedly and understandably missing some – and includes representatives from 42 plant families and 21 plant orders. Plantlets are the most common form of aerial vegetative diaspore at 116 taxa, with bulbils coming in second at 72. Cormlets and tubercles are less common, with 25 and 16 taxa respectively. Their paper includes the full list and offers further information about many of the species listed. It’s worth taking time to explore and is a valuable resource for anyone interested in the topic. In addition, their discussion section highlights a number of questions that warrant further investigation.

Questions surrounding reproductive strategies and the dispersal of aerial vegetative diaspores are particularly interesting. Because these structures are vegetative, they are essentially clones of the parent plant, meaning there is no genetic mixing as occurs when seeds are produced. This can be an advantage when sexual reproduction isn’t possible due to lack of pollinators, environmental restrictions, or chromosomal/polyploidy anomalies. It also assures that new individuals are pre-adapted to the site, and it can help a species colonize an area quickly. This ability to rapidly colonize explains why several of the species on Kona and Howard’s list are known to be invasive in parts of the world outside of their native range.

A species that produces both seeds and aerial vegetative diaspores may have an advantage when it comes to dispersal since both types of diaspores have their strengths. Seeds can remain dormant in the soil and are likely to persist in the environment longer than vegetative diaspores, but vegetative diaspores can be produced without relying on pollinators and can establish new individuals quickly. The modes of dispersal between the two can also vary. Seeds can be dispersed by wind or carried away by animals, while vegetative diaspores often rely solely on gravity to get around. One exception is hitchhiker elephant ear (Remusatia vivipara), whose bulbils are equipped with tiny hooks that cling to animal fur and are transported in a similar manner to burs.

hooked bulbils of hitchhiker elephant ear (Remusatia vivipara) (wikimedia commons; Dinesh Valke)

When the advantages of aerial vegetative diaspores are considered, it is a wonder that we don’t see them more often. Many plants can be easily propagated by taking stem, leaf, and/or root cuttings and placing them in conditions that favor adventitious root and shoot growth. This may suggest that dormant genetic pathways for producing vegetative diaspores exist in most plants. Or maybe not. Genetic studies of species that feature these structures are needed in order to understand why they are found in some species and not others. Kona and Howard leave us with a slew of research questions like this, and it’s a topic I’ll continue to check in on.


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