spontaneous urban plants

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Highlights from the Western Society of Weed Science Annual Meeting 2023

As soon as I learned that the Western Society of Weed Science‘s annual meeting was going to be held in Boise in 2023, I began making plans to attend. I had attended the annual meeting in 2018 when it was held in Garden Grove, California and had been thinking about it ever since. It’s not every year that a meeting like this comes to your hometown, so it was an opportunity I knew I couldn’t miss. The meeting was combined with the Western Aquatic Plant Managment Society‘s annual meeting, so consider that a bonus.

The first meeting of the week was the general session where introductions are made and various updates are given. There were two keynote addresses as well. One highlight for me was learning about Women of Aquatics, which is a support group for women that work in aquatic sciences. Because this and so many other scientific fields tend to be male dominated, it’s good to see organizations offering support and creating community to help address some of the challenges women face when working in fields where they are underrepresented. Another highlight was Matt Germino‘s talk about fire ecology in the sagebrush steppe. Due to decades of overgrazing and the introduction of a suite of invasive annual grasses (among other factors), fire has become far more common in our region than it once was. The sagebrush steppe is not adapted to frequent fire, which is part of what makes restoration work so difficult. In 2015, a megafire (referred to as the Soda Megafire) occurred in the Owyhee Mountains, burning around 279,000 acres of sagebrush steppe. Restoration efforts after the fire have been well researched, and such efforts continue to this day. Research opportunities like this are helping us improve the way we address this issue in the West, and I hope to spend future posts elaborating further on this topic.

After the general ssession, I attended a few of the talks that were happening in the various breakout sessions. One was about climate change trends in the western U.S. No surprise, temperatures are on the rise, and along with that will come changes in the way we receive our preciptation (which has already been documented). Our region is expected to see more rain and less snow, and rain events are expected to be of shorter duration but with heavier rainfall. Snowpack is expected to continue to decrease, and drought is expected to become more extreme, which ultimately leads to more fire weather days. None of this is great news, but it’s important to understand what we are in for. I also attended a talk about non-target impacts that can arise from certain herbicde treatments used to control bird cherry (Prunus padus) in Alaska, which brought me back to my time attending the Alaska Invasive Species Workshop in Anchorage.

Posters!

The following day, the breakout sessions continued, and dozens of talks were given throughout the day. It’s impossible to attend them all, and unfortunately a few of the talks that I really wanted to hear were cancelled. One interesting talk that I’m glad I got to see was about liquid-applied cellulosic mulches used to replace polyethylene sheet mulches (black plastic) in strawberries and other crops. The results seen so far seem promising, and I’m eager to follow this topic to see where it goes and hopefully even try it out myself one day.

During the meeting, there were also a series of posters on display that summarized research being doing by some of the attendees. I didn’t get a chance to read them all, but a few standouts included posters about using prescriptive grazing to help control tall oatgrass (Arrhenatherum elatius) populations in Colorado, using an electrical current to help manage weeds in blueberry farms, and weed seed predation by ground beetles in diversified wheat production cropping systems. If a poster is about some form of novel or underused method of weed management, I’m definitely going to read it.

bur chervil (Anthriscus caucalis) in downtown Boise

It might seem a little odd for me to be attending meetings like this, especially since I don’t work as a weed scientist or in weed management, and much of what is discussed, namely presentations about all the various herbicide treatments used in rangelands, turfgrass, and large-scale agriculture, don’t concern me (nor do they really interest me). Talks like this are what you would expect to hear at a weed science conference, so despite not being my thing, I appreciate that such talks often include discussions about herbicide resistance and the responsible use of herbicides, climate change, drought and responsible water use, and adaptive management approaches to weed control. I’m not sure when I’ll get a chance to attend this meeting again – it may be another 5 years or more – but whenever the opportunity presents itself, I’ll be there.

Next Up: Botany 2023 is coming to Boise in July. I’ll see you there!

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Weeds of Boise: Hellstrip on Jefferson Street

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 salsify
knotweed (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)
  • Epilobium brachycarpum (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?

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Weeds of Boise: Ahavath Beth Israel Synagogue Garden

Anyone who has maintained a garden or small farm knows that with all the work it takes to keep up on the garden itself, outlying areas can quickly become overtaken by weeds. Low on the list of priorities, areas outside of our garden borders are ideal locations for wild urban vegetation to thrive. Pulling all the weeds within the garden is a big enough task as it is; thus, weeds out of our reach are left to their own devices, occasionally getting mown down by a string trimmer or brush mower (if time allows), but otherwise living largely unscathed. And so, places such as these are excellent for familiarizing oneself with our wild urban flora.

I found an example of this scenario at the Ahavath Beth Israel Synagogue Garden in Boise, Idaho. This community garden is a partnership between Congregation Ahavath Beth Israel (CABI) and Global Gardens, providing refugees in the area an opportunity to grow food for their families and participate in community activities.

When I visited this site, it was clear that the weeds on the edge of the garden had been mowed down at some point. New plants had popped up after the fact while others were in the process of recovering from the “haircut” and putting on new, shrubbier growth. The mowing and the fact that it was late in the summer made identifying remnants of earlier weeds too difficult to bother. Most of the weeds that I did find were either summer annuals or perennials. A visit in the spring would reveal an entirely different cast of characters.

I stayed on the border of the garden, not wanting to invade anyone’s plot or snoop around too much. The point of the visit was to highlight weeds found outside of the borders of a garden anyway. I would imagine that, since the garden is used to grow annual fruits and vegetables, most of the weeds in the beds would be annuals as well. Longer-lived weeds don’t generally tolerate regular disturbance and instead find refuge in unkept areas outside of cultivation.

Below are a few photos from the site along with a preliminary list of the weeds that I found.

salsify (Tragopogon dubius)

puncture vine (Tribulus terrestris)

field bindweed (Convolvulus arvensis)

Siberian elm (Ulmus pumila)

common mallow (Malva neglecta)

black medic (Medicago lupulina)

Weeds found at the Ahavath Beth Israel Synagogue Garden:

  • Amaranthus spp. (pigweed)
  • Bassia scoparia (kochia)
  • Chenopodium album (lamb’s quarters)
  • Chondrilla juncea (rush skeletonweed)
  • Convolvulus arvensis (field bindweed)
  • Conyza canadensis (horseweed)
  • Digitaria sanguinalis (crabgrass)
  • Epilobium brachycarpum (tall annual willowherb)
  • Euphorbia maculata (spotted spurge)
  • Hordeum jubatum (foxtail barley)
  • Lactuca serriola (prickly lettuce)
  • Malva neglecta (common mallow)
  • Medicago lupulina (black medic)
  • Oenothera biennis (common evening-primrose)
  • Plantago lanceolata (narrowleaf plantain)
  • Polygonum aviculare (prostrate knotweed)
  • Rumex crispus (curly dock)
  • Setaria sp. (foxtail)
  • Sonchus sp. (sow thistle)
  • Taraxacum officinale (dandelion)
  • Tragopogon dubius (salsify)
  • Trifolium pratense (red clover)
  • Ulmus pumila (Siberian elm)
  • Verbena bracteata (prostrate vervain)

Like all posts in the Weeds of Boise series, this will be updated as I identify and photograph more of the weeds found in this location.

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Weeds of Boise: Abandoned Pizza Hut on Ann Morrison Park Drive

There is an old Pizza Hut on the corner of Ann Morrison Park Drive and Lusk Street. I’m not sure how long it’s been closed (if someone knows for sure, please let me know), but it has to be well over a year – probably several years. It’s clear that the landscaping has not been maintained for a while. The turf grass in the hellstrips is now mostly weeds, the Callery pears and crabapples are in need of some serious pruning, and the mugo pines and horizontal junipers are slowly dying off. On the other hand, the Oregon grapes and barberries look just fine. They never really needed our help anyway.

I like checking out lots with recently abandoned buildings because you can see in real time just how quickly weeds take over once humans stop their meddling. As the months and years pass, and as the plants that humans intentionally placed there decline, it becomes increasingly obvious that weeds truly are the wild flora of our cities.

My first few visits to this site were on March 21st, 25th and 28th of 2020. During those visits, I made a list of all the weeds that I could easily identify and noted a few individuals that I will need to come back to. What follows are photos of a few of the weeds I came across, along with a list of the weeds I was able to identify.

Every lot needs a dandelion (Taraxacum officinale).

Common mallow (Malva neglecta) in mulch.

The turf grass in the hellstrips has been replaced by several different weeds including tiny, early spring favorites like bur buttercup (Ceratocephala testiculata) pictured here and spring draba (Draba verna).

Common groundsel (Senecio vulgaris) is prolific in a bed on the north side of the building. On the east side, this plant had already flowered and gone to seed by mid-March.

The tough taproot of alfalfa (Medicago sativa) easily works its way into cracks in pavement and concrete.

A bull thistle rosette (Cirsium vulgaris) perhaps?

Cheatgrass (Bromus tectorum) was common on the site, including (perhaps not surprisingly) in this parking block.

horseweed seedling (Conyza canadensis)

Weeds found at the abandoned Pizza Hut on Ann Morrison Park Drive:

  • Bromus tectorum (cheatgrass)
  • Ceratocephala testiculata (bur buttercup)
  • Cirsium vulgare (bull thistle)
  • Conyza canadensis (horseweed)
  • Draba verna (spring draba)
  • Hordeum murinum ssp. glaucum (smooth barley)
  • Lactuca serriola (prickly lettuce)
  • Malva neglecta (common mallow)
  • Medicago sativa (alfalfa)
  • Poa bulbosa (bulbous bluegrass)
  • Rumex crispus (curly dock)
  • Senecio vulgaris (common groundsel)
  • Taraxacum officinale (dandelion)
  • Ulmus pumila (Siberian elm)

This post will be updated as I identify more of the weeds and capture more photos. I also anticipate that this lot will not be abandoned for that much longer. It’s located near Boise State University in an area that has seen a lot of development in the past few years. I can’t imagine prime real estate like this will stay feral indefinitely. Until something is done with it, I’ll keep checking in.

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Introducing Weeds of Boise

Weeds are the wild flora of our cities. Their occurrence and continued existence is not directly reliant on humans in the same way that the plants in our yards, parks, gardens, and other green spaces are. They may take advantage of the disturbance that we cause when we stir up the soil or cease maintenance in a particular spot, and they certainly appreciate the runoff from our sprinklers and the free rides their seeds get on our pets and ourselves, but they don’t need us looking after them to survive. They get by on their own whether we approve of them or not. Most may not be native to the area, but their presence is natural – undirected and involuntary – and for this reason I consider them to be a valid component of our urban flora.

If you visit a natural area outside of our cities, you are likely to find a field guide associated with that region that will help you identify many of the plants found there. However, such a field guide is not likely to exist for the plants found in a vacant lot or an urban roadside near you. Sure, there are plenty of general weed identification guides, some of which may be specific to where you live, but they are often focused on agricultural/horticultural weeds or weeds found in natural areas outside of the built environment. Few show weeds in an unmaintained urban setting the way that Peter Del Tredici’s book or Maggie Herskovits’ zine do. Clearly we need more resources that identify and document our urban floras.

Weeds of Boise is an attempt to begin that process for my corner of the world. After coming across websites like The Weedalouge (cataloging the wild plants of Philadelphia), Weeds of Melbourne (“a visual glossary of the weedy heritage of Melbourne, Australia”), and Spontaneous Urban Plants (an attempt to map weeds in urban areas around globe), I decided to start the process here in Boise, Idaho. My goal is to select locations across the city and inventory the weeds found there at different times of the year. I will keep a running list of what I find and photograph as many plants as I can. I will make a separate blog post for each location and maintain a link for each post in the Weeds of Boise page. The blog posts will be updated as I collect more data for each site. Over time I hope to have a more clear picture of what weeds are found here and how they are distributed.

Because many of these plants are cosmopolitan, the weeds found in my area are likely similar to the ones found in yours, but there may be some unique differences. If more projects like this are undertaken, we will have a better idea of the similarities and differences among our urban floras. Upon closer observation, we are likely to make some interesting discoveries. Who knows what we might find once we really start looking at these obnoxiously ubiquitous but otherwise completely ignored plants?

Weeds of Boise is also a reminder that you can botanize anytime anywhere. You don’t have to jet off to some remote location to see plants. It’s likely that there are wild plants growing right outside your front door – each one with a unique name and story and just as worth getting to know as any other.

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Zine Review: An Urban Field Guide to the Plants in Your Path

Depending on where you live in the world, it’s probably not too difficult to find a field guide to the plants native to your region. In fact, there may be several of them. They may not cover all the plants you’ll encounter in natural areas near you, but they’ll be a good starting point. Yet, considering that most of us live in cities these days, field guides to the wild plants of urban areas are sorely lacking. Perhaps that’s no surprise, as plants growing wild in urban areas are generally considered weeds and are often the same species that frustrate us in our yards and gardens. Few (if any) of these maligned plants are considered native, so that doesn’t help their case any. Why would we need to know or pay attention to these nuisance plants anyway?

I argue that we should know them, and not just so that we know our enemy. Weeds are the wild flora of our cities – they grow on their own without direct human intervention. In doing so, they green up derelict and neglected sites, creating habitat for all kinds of other organisms and providing a number of ecosystem services along the way. Regardless of how we feel about them for invading our cultivated spaces and interfering with our picture-perfect vision of how we feel our cities should look, they deserve a bit more respect for the work they do. If we’re not willing to go that far, we at least ought to hand it to them for how crafty and tenacious they can be. These plants are amazing whether we want to admit it or not.

Luckily I’m not the only who feels this way. Enter An Urban Field Guide to the Plants in Your Path, a zine written and illustrated by Maggie Herskovits and published by Microcosm Publishing. This zine is just one example of the resources we need to better familiarize ourselves with our urban floras. While there are many weed identification books out there, a field guide like this differs because it doesn’t demonize the plants or suggest ways that they can be brought under control or eliminated. Instead, it treats them more like welcome guests and celebrates some of their finer qualities. That being said, this is probably not a zine for everyone, particularly those that despise these plants, but take a look anyway. If you keep an open mind, perhaps you can be swayed.

Illustration of Pennsylvania smartweed (Polygonum pensylvanicum) from An Urban Field Guide to the Plants in Your Path

After a brief introduction, Herskovits profiles fifteen common urban weeds. Each entry includes an illustration of the plant, a short list of its “Urban Survival Techniques,” a small drawing of the plant in its urban habitat, and a few other details. The text is all handwritten, and the illustrations are simple but accurate enough to be helpful when identifying plants in the wild. The descriptions of each plant include interesting facts and background information, and even if you are already familiar with all the plants in the guide, you may learn something new. For example, I wasn’t aware that spotted spurge (Euphorbia maculata) was native to North America.

some urban survival techniques of common mullein (Verbascum thapsus)

Capsella bursa-pastoris in its urban habitat

Urban weeds often go ignored. They may not be as attractive as some of the plants found in gardens and parks around the city, and since they are often seen growing right alongside garbage, they end up getting treated that way. But if you’re convinced that they may actually have value and you want to learn a bit more about them, this guide is a great place to start. Perhaps you’ll come to feel, as Herskovits does, that “there is hope in these city plants.”

See Also: 

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Book Review: What Weeds Are Thinking

Plant intelligence is a burgeoning field of research. Despite being predominantly sessile organisms, plants are able to sense their surroundings and make decisions based on environmental cues. In a certain sense, they can see, hear, smell, and remember even though they don’t have eyes, ears, noses, or brains. Not surprisingly, these fascinating findings have spawned books, podcasts, documentaries, articles, etc. The idea that plants could be intelligent beings like us is something that captures our attention and imagination.

For example, if plants are so smart, does this mean that they actually have thoughts? And if they have thoughts, what could they possibly be thinking? In her new book, What Weeds Are Thinking, Erica Crockett takes a stab at what a particularly despised group of plants might think if, indeed, they could have thoughts. Weeds are, in Crockett’s words, “the deviants of the plant world.” This book was her chance to imagine what might be going on inside the minds of these deviants, despite the fact that they don’t have minds.Crockett conjures up the thoughts of 21 different weeds. Each thought is accompanied by an illustration by Sarah Ragan Olson. The drawings are charming, but the thoughts that juxtapose them aren’t always so sweet. Perhaps you imagine weeds to be potty mouthed? Well, so does Crockett. That being said, this book is not for kids, nor is it for anyone sensitive to adult words and themes. Each of the weeds in this book varies in its degree of irreverence – not all of them are so crass and some of them are actually pretty mild-mannered – but that’s just what you’d expect from such a diverse group of plants.

Comfrey is offended by cow manure being used as fertilizer and would rather be fertilized by “the decaying corpses of [its] relations.” Ground ivy is embarrassed and offended by inadvertently seeing the ankles of human passersby.  Plantain is apparently into being stepped on, and prostrate spurge is trying to “rebrand” to make itself more appealing and set itself apart from purslane. Cheatgrass, no surprise here, comes across as a big jerk. Originally from Eurasia, it is now a freedom-loving American, “choking out the rights of the natives.”

Most in line with what I would expect a weed to be thinking – especially one found growing in an urban area – is prickly lettuce. Upset after watching a fellow member of its species ruthlessly dug up, it laments: “Neither of us decided to seed down in the deep crack of this suburban driveway. We were blown here…It’s our home…Yet we are hunted.”

Milkweed is quite aware of its role as the sole food source of the monarch caterpillar. It sees how much humans appreciate monarchs, and admonishes us for killing off its kind: “Keep it up, and I’ll take every last one of those delicate darlings down with me.”

Botanical inaccuracies aside – and there are several – this was a fun book. The main appeal for me is that it is plant-themed and, more specifically, weeds-themed. If you follow this blog, you’ll know that pretty much anything involving weeds is going to get my attention. Beyond that, any project that puts plants in the spotlight and gives them a voice (even in a fictitious sense) is worth checking out. This book is no exception.

As a bonus, I asked Erica Crockett what other plants (apart from weeds) are thinking. This was her response: “Probably really precious or intellectual things. I imagine tomato plants are fairly self-important and zonal geraniums are divas. Bougainvilleas are likely social climbers and oak trees are dull, but honest.”

More Weeds-themed Book Reviews on Awkward Botany:

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Spring Weeds in the Mustard Family

Is there a plant family that consists of more weedy species than the mustard family? Asteraceae and Poaceae, for sure. Fabaceae or Lamiaceae, perhaps. Regardless, Brassicaceae is replete with dozens of species – mostly annual – that are skilled at taking advantage of the disturbed environments that humans are in the habit of creating.

It helps that the mustard family is so large: 372 genera and over 4,000 species distributed across the globe. Around 55 genera are said to occur in North America. Most of the plants in this family are herbaceous; few are shrubs. Foliage is aromatic, especially when crushed. Flowers are particularly distinctive. Each flower has four petals – in some species petals are divided, giving the impression that there are more than four – arranged in the shape of a cross or “X.” Flowers are often small, have 4 tall stamens and 2 short stamens, and commonly come in white, yellow, pink, or purple. They are arranged on a raceme, which is typically either tall and straight or compact and flat-topped.

Fruits in the mustard family are capsules with two compartments separated by a clear membrane. The capsules may be at least three times longer than they are wide, in which case they are referred to as a silique; or they may be less than three times longer than they are wide and referred to as a silicle. This is a curious distinction, and it doesn’t tell you all that much. It’s more important to understand that the capsules of mustards can come in various sizes and shapes, and that some can be long and narrow while others are short and either round or angular.

mustard seeds via wikimedia commons

Despite the size or shape of the capsule, enclosed are numerous seeds – sometimes dozens. Surely one of the reasons why plants in the mustard family are so successful at proliferating is their ability to produce thousands, even tens of thousands, of seeds per plant. The seeds are typically tiny; and while they may not make it very far from the parent plant, they are numerous. Depending on the species, they can also remain viable for years, affording them the opportunity to sprout whenever conditions are right. You may have heard the biblical verse about faith the size of a mustard seed giving one the ability to move mountains. Size seems irrelevant here, so how about faith as tough, resilient, opportunistic, and resourceful as a mustard seed? If a mountain can be moved, mustards might be the one to do it.

While it isn’t the scope of this post, it’s worth mentioning the chemical compounds present in mustards that give them the flavors and health benefits we enjoy as well as the toxicity that can harm us and any other organisms that dare consume them. Glucosinolates, which are present in various concentrations depending on the species, are a defining characteristic of plants in the mustard family. They contribute to the spicy-ness of things like horseradish, radish, and condiment mustard while also acting as a natural insecticide, deterring herbivory.

And now on to the cast of characters:

Whitetop (Lepidium spp.)

Garlic mustard (Alliaria petiolata) – a noxious weed in many parts of North America – is fortunately not an issue in southwestern Idaho, otherwise it would be first on the list. Instead, we deal with whitetop – a noxious weed in Idaho and several other states. As the common name suggests, individual plants – up to two feet tall – are topped with a dense cluster of tiny, white flowers. Seed production in this group isn’t as abundant as other mustards; instead, the tour de force are their rhizomes. Whitetop is a perennial plant that spreads aggressively via underground stems as well as root fragments and can easily form expansive, dense patches, outcompeting other plants in the area.

Another common name for this group is hoary cress on account of their gray-green, fuzzy foliage. They are further distinguished by the shape of their seed pods: lens-podded hoary cress (L. chalepense), heart-podded hoary cress (L. draba), and globe-podded hoary cress (L. applelianum).

white top (Lepidium sp.)

white top (Lepidium sp.)

Tansymustard (Descurainia spp.)

There are two species of tansymustard (also known as flixweed) that occur in my part of the world, one is native and the other is introduced from Europe. They are indistinguishable to my untrained eye. If I have seen them side by side, I wouldn’t have known it. They are both annuals and can be as short as a few inches to over two feet tall. They have highly dissected, fern-like leaves and tiny, pale yellow or green-yellow flowers. The seed pods are very skinny and around an inch long. Each pod can hold 40 seeds, and a large plant can produce over 75,000 seeds. They are quick to take advantage of disturbed soil and come up in abundance after a fire. I’m not sure what it is about this year, but they have been particularly prolific this spring.

tansymustard (Descurainia sp.)

tansymustard (Descurainia sp.)

Blue Mustard (Chorispora tenella)

Also known as musk mustard or crossflower, this sticky, stinky, annual plant apparently makes cow’s milk taste funny; however some people still enjoy eating it. It can get to about a foot and a half tall, and is adorned with pretty, little, blue-purple flowers. The pointy seed pods split crosswise rather than lengthwise, an uncommon trait in mustards.

blue mustard (Chorispora tenella)

blue mustard (Chorispora tenella)

Desert Madwort (Alyssum desertorum)

Like tansymustard, this species is very similar in appearance to another closely related species, Alyssum alyssoides (commonly known as pale madwort or yellow alyssum). Both are annuals under a foot tall, covered in tiny hairs, with minuscule yellow flowers, and numerous round seed pods. They are adapted to dry, neglected sites.

yellow alyssum (Alyssum dessertorum)

Annual Honesty (Lunaria annua)

If you don’t recognize this plant when it’s flowering, you will when its seed pods ripen. They are thin, round discs up to three inches across. Eventually, the outer layers of the seed pods fall away, and translucent membranes remain, sometimes with seeds still attached. This trait has earned this species common names like money plant and silver dollar. The plants are attractive, reach up to three feet tall, and produce showy, purple flowers, which explains why they are popular ornamentals. However, like other mustards, the proficiency with which they reproduce in abundance via seeds, means they also easily migrate into natural areas and neglected sites.

annual honesty (Lunaria annua)

Hairy Bittercress (Cardamine hirsuta)

This little, quick-growing, fast-spreading annual is a common nuisance in greenhouses and nurseries. On stalks above compact rosettes are borne clusters of white flowers that, as Ken Thompson writes in The Book of Weeds, “are so tiny they are almost invisible.” The slender seed pods burst open at maturity, sending minuscule seeds flying. Brush your hand over a patch of mature hairy bittercress and you will be bombarded.

hairy bittercress (Cardamine hirsuta)

And the list goes on…

I’ve observed several other weedy species in this family recently, but to keep the length of this post reasonable I will just list them here: shepherd’s purse (Capsella bursa-pastoris), clasping pepperweed (Lepidium perfoliatum), spring draba (Draba verna), tumble mustard (Sisymbrium altissimum), and pennycress (Thlaspi arvense). This list only scratches the surface; there are many other weeds in the mustard family. All deserve to be mentioned, so perhaps another time.

See Also: In Defense of Plants – One Mustard, Many Flavors

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What Bugs Can Tell Us About the Value of Vacant Urban Land

Back in October 2017, we discussed some potential benefits of spontaneous urban vegetation (commonly referred to as weeds) and the abandoned or undeveloped urban spaces they inhabit. There is much to learn about the role these plant communities play in the ecology of cities and their contribution to vital ecosystem services. In a review published in the December 2013 issue of Environmental Entomology, researchers from Ohio State University discuss how studying arthropod communities on vacant lands can help “advance our ecological understanding of the functional role” these habitats may have in our cities.

Arthropods were selected as the subject of study because their “populations respond quickly to changes in the urban environment, making them key indicators of how land use change influences biodiversity.” Urban-dwelling arthropods “are diverse and occupy multiple trophic levels” and are “easy to sample.” Additionally, many of the services that vacant, unmanaged land offers are “arthropod-mediated,” including “pollination, decomposition, nutrient cycling, and biological pest control.”

photo credit: wikimedia commons

Vacant land was selected as the study site because “understanding [its] ecological value is important to the advancement of urban ecology and ecosystem management,” and even though such areas are often overlooked in conservation planning, studies have shown that they “have the potential to be valuable reservoirs of biodiversity.” In order to determine just how valuable vacant land might be, more research is needed comparing these spaces to other parts of the city. In addition, vacant lots are generally ephemeral and in due time may be developed. Whether this means that a building or parking lot takes their place or that they are converted into a park, garden, or urban farm, it is important to understand what these land use changes mean for urban biodiversity and ecological functions.

Urbanization is often measured by comparing the amount of built area to the remaining green space. Where there is a high degree of urbanization, there is a low degree of green space comparatively. As urbanization increases, so does habitat fragmentation, pollution, and the urban heat island. In the meantime, biodiversity suffers. The authors cite a number of studies demonstrating that increased urbanization negatively impacted beneficial insect populations. For example, a study in the United Kingdom found that bumblebee diversity in gardens “decreased with increasing urbanization of the surrounding landscapes.” Similar results were found in a study we wrote about.

photo credit: wikimedia commons

Together with remnant natural areas, parks, private and public gardens, greenways, and commercial landscapes, vacant lots are part of a mosaic of urban green space. Each of these areas “experience different levels of disturbance and harbor varying plant species,” which, in turn, “influence arthropods and the services they can supply within and between patches.” Because vacant lots can remain undisturbed and virtually unmanaged for long periods of time, they help provide a contrast to the homogeneous, highly managed green spaces that are common in cities. By their very nature, they “have the potential to aid conservation and enhance green space quality and connectivity within city centers.”

It’s one thing to recognize the value of vacant lots; it’s another thing to change the negative perception of them. Aesthetics are important, and to many people vacant lots are an eyesore and a sign of neglect. Some management may be necessary in order to retain their important ecological value and assuage the feelings of the public. The authors present a number of ways that vacant lots can be and have been managed in order to achieve this goal. They also consider how certain management strategies (mowing, removing and/or introducing plant species) can impact arthropod populations for better or worse. Yet, where vacant lots are left alone and allowed to advance in the stages of ecological succession, changes in arthropod diversity and ecosystem function also occur. For this reason, “the regional species pool of a city requires a mosaic of all successional stages of vacant land patches.”

photo credit: wikimedia commons

Finally, the authors discuss the conversion of vacant land to urban agriculture. Even this land use change can have dramatic effects on the arthropod community. For example, undisturbed or unmanaged areas are a habitat requirement for cavity and soil nesting bees, and regular disturbance associated with farming may interfere with this. Also where pesticides are used or plant diversity is minimized, the arthropod community will be affected.

Thus, “the study of vacant land ecology necessitates a transdisciplinary approach” in order to determine how changes in vacant, urban land “will affect diverse ecosystem functions and services.” A variety of management strategies are required, and land managers must “determine the most appropriate strategies for improving the sustainability of cities from a connected landscape perspective.” It is clear that vacant lots have a role to play. The extent of their role and our approaches to managing them requires careful investigation.

One thing is certain – for biodiversity’s sake – don’t pave over vacant lots to put up parking lots.

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Weeds and Winter Interest

In climates where winter sucks the garden inside itself and into quiet dormancy, it is often dead stalks and seed heads that provide the most visual interest. They also become, in some respects, a reminder of a garden that once was and what will be again.” — Gayla Trail, Grow Curious

If, like me, it is during the growing season that you really thrive, winters can be brutal. Color has practically been stripped from the landscape. Death and slumber abound. Nights are long and days are cold. It’s a lengthy wait until spring returns. Yet, my love of plants does not rest. And so, I look for beauty in a frozen landscape.

In evergreens, it is obvious. They maintain their color year-round. Large bunchgrasses, shrubs and trees with interesting bark or branching habits, dried fruits and unique seed heads – all of these things are easy to spot and visually interesting.

Beyond that, there are things that we are not accustomed to finding beauty in. Such things require a keen eye, close observation, and the cultivation of greater understanding and appreciation. For most people, weeds fall into this category. What is there to love or find beautiful?

I am of the opinion that there is plenty there to intrigue us. From their spent flowers to their seed heads and dried-up leaves, they can be just as interesting as the plants we deem more desirable. The winter-long green of winter annuals alone is evidence enough. So, here is my attempt to redeem some of these plants by nominating them as candidates for winter interest.

common mallow (Malva neglecta)

field bindweed (Convolvulus arvensis)

common mullein (Verbascum thapsus)

common dandelion (Taraxacum officinale)

Russian thistle (Kali tragus, syn. Salsola tragus)

Russian thistle (Kali tragus, syn. Salsola tragus)

redstem filaree (Erodium cicutarium)

curly dock (Rumex crispus)

curly dock (Rumex crispus)

prickly lettuce (Lactuca serriola)

salsify (Tragopogon dubius)

wood avens (Geum urbanum)

yellow evening primrose (Oenothera biennis)

annual honesty, a.k.a. money plant (Lunaria annua)

white clover (Trifolium repens)

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A friendly reminder: Refrain from being overly ambitious with your fall cleanup and, instead, leave certain plants in place. This not only provides winter interest but can also be beneficial to the wild creatures we share space with.