Growing plants in urban areas comes with a variety of challenges. Soil conditions aren’t always ideal; shade thrown by buildings and other structures can be difficult to work around; paved surfaces lead to compaction and, among other things, can increase temperatures in the immediate area; and in locations where water is limited, keeping plants hydrated is a constant concern. One location that tends to be especially difficult for gardeners is the hellstrip – the section of ground between a roadway and a sidewalk. Much can be said about gardening in hellstrips, so much that there is even a book about it called Hellstrip Gardening by Evelyn Hadden, which I spent several posts reviewing a few years back.
The difficulty of maintaining a hellstrip (and perhaps questions about who is responsible for maintaining it in the first place) can result in it being a piece of property frequently subject to neglect. In urban areas, neglected land is the perfect place for weeds to take up residence. The conditions in a hellstrip being what they are – hot, dry, frequently trampled, and often polluted – also gives weeds a chance to show what they can do. It’s a wonder that any plant can survive in such conditions, but the wild flora of our cities consists of some pretty tough plants, and a hellstrip is an excellent location to familiarize yourself with some of these plants.
On a walk with Kōura, I came across a weedy hellstrip on Jefferson Street in downtown Boise. Many of the classic hellstrip challenges are present there – it’s surrounded by paved surfaces, there is lots of foot traffic in the area, parking is permitted on the roadside, urban infrastructure (street signs, parking meters, stoplights) is present within the strip. It’s clear that at one point the area was being maintained as irrigation is installed and there are remnants of turfgrass. Three honey locusts were also planted in the strip, one of which has clearly died. Now that maintenance seems to have ceased, weeds have become the dominant flora in this hellstrip. What follows are a few photos and a list of the weeds I’ve identified so far. Like all posts in the Weeds of Boise series, this list may be updated as I continue to check back in on this location.
shepherd’s purse (Capsella bursa-pastoris) and prickly lettuce (Lactuca serriola)dandelion (Taraxacum officinale)salsify (Tragopogon dubius)seed head of salsifyknotweed (Poylgonum sp.)prickly lettuce (Lactuca serriola)mallow (Malva neglecta)orchard grass (Dactylis glomerata)
Bromus tectorum (cheatgrass)
Capsella bursa-pastoris (shepherd’s purse)
Dactylis glomerata (orchard grass)
Epilobiumbrachycarpum (tall willowherb)
Lactuca serriola (prickly lettuce)
Malva neglecta (dwarf mallow)
Polygonum sp. (knotweed)
Salsola sp. (Russian thistle)
Taraxacum officinale (dandelion)
Tragopogon dubius (salsify)
Trifolium repens (white clover)
Vulpia myuros (rattail fescue)
Are there unkept hellstrips in your neighborhood? If so, what weeds have you seen taking up residence there?
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.
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.
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.”
Let’s start by getting something out of the way: roses have prickles, not thorns. However, just like peanuts aren’t actually nuts and tomatoes are actually fruits, our colloquial terms for things don’t always match up with botanical terminology. This doesn’t mean that we should be pedants about things and go spoiling a friendly dinner party with our “well, actually…” corrections. If you hear someone saying (or singing) something about every rose having its thorn, it’s okay to just let it go.
So why don’t roses have thorns? And what even is a prickle anyway?
Plants have a way of modifying various body parts to form a variety of features that look like something totally new and different. When the development of these features are observed at a cellular level, we find that what once may have grown into something familiar, like a stem, is now something less familiar, like a thorn. A thorn, then, is a modified stem. Stem tissue was used by the plant to form a hardened spike. Thorns help protect a plant from being eaten, so going through the trouble of producing this feature is a benefit to the plant.
thorns of hawthorn (Crataegus sp.)
Spines and prickles are similar features to thorns and serve a similar purpose, but they have different origins. Spines are modified leaf or stipule tissue (the spines on a cactus are actually modified leaves). Prickles are outgrowths of the epidermis or bark. In plants, epidermis is a single, outer layer of cells that covers all of the organs (i.e. leaves, roots, flowers, stems). Outgrowths on this layer are common and often appear as little hairs. The technical term for these hairs or hair-like structures is trichomes.
the stems of staghorn sumac (Rhus typhina) are covered in dense trichomes
Prickles are much like trichomes, but there are usually less of them and they are hardened and pointy. They can be sharp like a thorn or spine and so are often confused for them. (Spines are also confused for thorns, as is the case with Euphorbia milii, whose common name is crown of thorns but whose “thorns” are actually spines.) As stated above, their cellular origin is different, and unlike thorns and spines, prickles don’t have vascular tissue, which is the internal tissue that transports water and nutrients throughout all parts of the plant. In general, prickles can be easily broken off, as they are often weakly attached to the epidermis.
Prickles are most commonly observed on roses and come in a variety of shapes, sizes, and colors.
Prickles on roses are commonly called thorns, and that’s okay. Thorn is perhaps a more poetic word and easier to relate to. But really, I’m torn and forlorn that they aren’t thorns. It puts me in a pickle trying to rhyme words with prickle.
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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.
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.
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.
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 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.
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.
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.
At first glance, a tulip and a tulip tree couldn’t be more different. One is a bulb that puts out fleshy, green leaves in the spring, topped with colorful, cup-shaped flowers, barely reaching a foot or so tall. The other is a massive, deciduous tree with a broad, straight trunk that can grow to nearly 200 feet tall. But if you can get a look at the flowers, seed heads, and even the leaves of this enormous tree, you might see a resemblance – at least in the shape of these features – to one of our most popular spring flowering geophytes.
Tulip tree (Liriodendron tulipifera) is distributed across the eastern United States and has been planted widely outside of its native range. Also commonly known as tulip poplar, yellow poplar, and whitewood, it is a member of the magnolia family and is one of two species in its genus (the other being Liriodendron chinense – a tree found mainly in China). Many (if not most) deciduous trees of North America have small, inconspicuous flowers, but tulip trees – like its close relatives, the magnolias – have relatively large, showy flowers. The trouble is actually getting to see them since, at least on mature trees, they are borne in a canopy that is considerably taller than the average human.
Tulip tree flowers are cup-shaped, yellow-green and orange, with a series of prominent stamens surrounding the carpels which are attached to a long, slender receptacle giving it a cone-shaped appearance. As the flower matures into fruits, the tulip shape of the inflorescence is maintained as the seeds with their wing-like appendages form a tight, cone-like cluster that opens as the seeds reach maturity. The wings aid in dispersal as the seeds fall from the “cone” throughout the winter.
seed head of tulip tree (Liriodendron tulipifera)
The four-lobed leaves of tulip trees also form a vague tulip shape. They are alternately arranged, bright green, and up to five or six inches long and wide, turning yellow in the fall. Two prominent, oval-shaped stipules surround the stem at the base of the petiole of each leaf. These stipules come into play when identifying the leafless twigs of tulip trees during the winter months.
leaf of tulip tree (Liriodendron tulipifera) in late summer
The winter twigs of tulip trees are easily recognizable thanks to their duck bill shaped buds which are made up of two wine-red, violet, or greenish bud scales. The terminal buds are considerably larger and longer than the lateral buds, some of which are on little stalks. The twigs are smooth, olive-brown or red-brown, with just a few, scattered, white lenticels. Leaf scars are rounded with a dozen or so bundle scars that are either scattered or form an irregular ellipse. Pronounced stipule scars encircle the twig at the location of each leaf scar. Twigs can be cut lengthwise to reveal pale white pith that is separated by a series of diaphragms.
winter twig of tulip tree (Liriodendron tulipifera)top right: the chambered pith of black walnut (Juglans nigra); bottom left: diaphragmed pith of tulip tree (Liriodendron tulipifera)
The bark of tulip trees can be easily confused with that of ash trees. Young bark is smooth and ash-gray to grayish green with pale, vertical cracks. As the tree matures, the cracks develop into furrows with flat-topped ridges. The ridges grow taller and more peaked, and the furrows grow deeper as the tree reaches maturity. In the book Winter Botany, William Trelease compares the mature bark of tulip trees to a series of parallel mountain ranges with deep gullies on either side.
maturing bark of tulip tree (Liriodendron tulipifera)
Perhaps even as tulips are blooming, the buds of tulip trees break to reveal their tulip-shaped, stipule bearing leaves. This makes for an interesting show. In The Book of Forest and Thicket, John Eastman describes it this way: “from terminal buds shaped like duck bills, successions of bills within bills uncurl and unfold, revealing a marvel of leaf packaging.”
It is said that the inspiration for Velcro came when Swiss inventor, George de Mestral, was removing the burrs of burdock from his dog’s coat, an experience we had with Kōura just days after adopting her. I knew that common burdock was found on our property, and I had made a point to remove all the plants that I could easily get to. However, during Kōura’s thorough exploration of our yard, she managed to find the one plant I had yet to pull due to its awkward location behind the chicken coop.
I knew when I saw the clump of burrs attached to her hind end that we were going to spend the evening combing them out of her fur. However, not long after that we discovered that Kōura had already started the process and in doing so had either swallowed or inhaled some. What tipped us off was her violent hacking and gagging as she moved frantically around the living room. She was clearly distraught, and so were we. Recognizing that she had probably swallowed a burr, we made a quick decision to take her to an emergency vet. This was our unfortunately timed (this happened on Christmas Eve) introduction to burr tongue and all the frightening things that can happen when a dog swallows burdock burrs.
The roots, shoots, and leaves of both greater burdock (Arctium lappa) and common burdock (Arctiumminus) are edible, which I have already discussed in an Eating Weeds post. The burrs, on the other hand, are clearly not. While sticking to the fur of animals and the clothing of people is an excellent way for a plant to get their seeds dispersed, the sharp, hooked barbs that facilitate this are not something you want down your throat. When this occurs, the natural response is to try to hack them up, which Kōura was doing. Salivating heavily and vomiting can also help. In many cases, this will be enough to eliminate the barbs. However, if they manage to work their way into the soft tissues of the mouth, tongue, tonsils, or throat and remain there, serious infection can occur.
burr of common burdock (Arctium minus)
A paper published in The Canadian Veterinary Journal in 1973 describes the treatment for what is commonly known as burr tongue and technically referred to as granular stomatitis. The paper gives an account of what can happen when “long-haired breeds of dogs … run free in areas where [burdock] grows” and the hooked scales of the burrs consequently “penetrate the mucous membrane of the mouth and tongue.” Dogs with burrs imbedded in their mouths may start eating less or more slowly, drinking more water, and drooling excessively. As infection progresses, their breath can start to stink. A look inside the mouth and at the tongue will reveal lesions where the burrs have embedded themselves. Treatment involves putting the dog under anesthesia, scraping away the infected tissue, and administering antibiotics. Depending on the severity of the lesions, scar tissue can form where the barbs were attached.
To prevent infection from happening in the first place, a veterinarian can put the dog under anesthesia and use a camera inside the dog’s mouth and throat to search for pieces of the burr that may have gotten lodged. There is no guarantee that they will find them all or be able to remove them, and so the dog should be monitored over the next several days for signs and symptoms. At our veterinary visit, the vet also warned us that if any burrs were inhaled into the lungs, they could cause a lung infection, which is another thing to monitor for since it would be practically impossible for an x-ray or a camera to initially find them.
Luckily, now more than three weeks later, Kōura appears to be doing fine, and the offending burdock has been taken care of. One thing is for sure, as someone who is generally forgiving of weeds, burdock is one weed that will not be permitted to grow at Awkward Botany Headquarters.
For more adventures involving Kōura, be sure to follow her on Instagram @plantdoctordog.
Last year at this time I was newly married in a new home that Sierra and I had just bought together. The year flew by, as they often do, and we’re back around to another Year in Review. Home ownership (among other things) has kept us busy. If you follow this blog, you may have noticed that posts were a bit more sparse than usual. That probably won’t change much going forward, but even if takes me some time to get around to posting, I plan to keep this blog going for the foreseeable future. There are still so many plants to investigate and botanical topics to explore. I hope you will follow along, even when posts are few and far between.
The big news of the day is that Sierra and I recently added a new member to our family. Not a human, but a dog. Her name is Kōura, and I would expect her to make an appearance from time to time both here on the blog as well as on our various social media accounts. We are excited for the many adventures we’ll be having with her in the months and years to come, and can’t wait to introduce her to the world.
Kōura in the snow on Christmas Day2021
As Awkward Botany enters its tenth year, I feel incredibly grateful for everyone who has supported it along the way. To everyone who has bothered to read a post, leave a comment, share the blog with a friend, and reach out to me by various means, I appreciate you all for participating in my silly, little, plant project. Plant people are the best. Luckily, supporting Awkward Botany is easy. Apart from reading and commenting on the blog, there are social media accounts to follow, monetary donations to make (no pressure), and books to buy from our Bookshop. All relevant links can be found on Awkward Botany’s linktree (link below). Let’s stay phytocurious in 2022!
awkward botany 