Eating Weeds: Blue Mustard

Spring is here, and it’s time to start eating weeds again. One of the earliest edible weeds to emerge in the spring is Chorispora tenella, commonly known by many names including blue mustard, crossflower, and musk mustard. Introduced to North America from Russia and southwestern Asia, this annual mustard has become commonplace in disturbed areas, and is particularly fond of sunny, dry spots with poor soil. It can become problematic in agricultural areas, but to those who enjoy eating it, seeing it in large quantities isn’t necessarily viewed as a problem.

rosettes of blue mustard (Chorispora tenella)

The plant starts off as a rosette. Identifying it can be challenging because the shape of the leaves and leaf margins can be so variable. Leaves can either be lance-shaped with a rounded tip or more of an egg shape. Leaf margins are usually wavy and can be deeply lobed to mildly lobed or not lobed at all. Leaves are semi-succulent and usually covered sparsely in sticky hairs, a condition that botanists refer to as glandular.

A leafy flower stalk rises from the rosette and reaches between 6 and 18 inches tall. Like all plants in the mustard family, the flowers are four-petaled and cross-shaped. They are about a half inch across and pale purple to blue in color. Soon they turn into long, slender seed pods that break apart into several two-seeded sections. Splitting apart crosswise like a pill capsule rather than lengthwise is an unusual trait for a plant in the mustard family.

blue mustard (Chorispora tenella)

Multiple sources comment on the smell of the plant. Weeds of North America calls it “ill-scented.” Its Wikipedia entry refers to it as having “a strong scent which is generally considered unpleasant.” The blog Hunger and Thirst comments on its “wet dish rag” smell, and Southwest Colorado Wildflowers claims that its “peculiar odor” is akin to warm, melting crayons. Weeds of the West says it has a “disagreeable odor,” and warns of the funny tasting milk that results when cows eat it. All this to say that the plant is notorious for smelling bad; however, I have yet to detect the smell. My sense of smell isn’t my greatest strength, which probably explains why I’m not picking up the scent. It could also be because I haven’t encountered it growing in large enough quantities in a single location. Maybe I’m just not getting a strong enough whiff.

Regardless of its smell, for those of us inclined to eat weeds, the scent doesn’t seem to turn us away. The entire plant is edible, but the leaves are probably the part most commonly consumed. The leaves are thick and have a mushroom-like taste to them. They also have a radish or horseradish spiciness akin to arugula, a fellow member of the mustard family. I haven’t found them to be particularly spicy, but I think the spiciness depends on what stage the plant is in when the leaves are harvested. I have only eaten the leaves of very young plants.

The leaves are great in salads and sandwiches, and can also be sauteed, steamed, or fried. I borrowed Backyard Forager’s idea and tried them in finger sandwiches, because who can resist tiny sandwiches? I added cucumber to mine and thought they were delicious. If you’re new to eating weeds, blue mustard is a pretty safe bet to start with – a gateway weed, if you will.

blue mustard and cucumber finger sandwiches

For more information about blue mustard, go here.

Eating Weeds 2018:


Poisonous Plants: Red Squill

Humans have been at war with rats since time immemorial. Ridding ourselves of their nuisance behavior is increasingly unlikely, and in fact, some scientists believe that, following human extinction, rats will be poised to take our place as the most dominant species on earth. Despite being thwarted repeatedly, we make tireless attempts to control rat populations. One major weapon in our arsenal is poison, and one of the most popular rat poisons was derived from a plant with a formidable bulb.

Urginea maritima (known synonymously as Drimia maritima, among other Latin names) is a geophyte native to the Mediterranean Basin, where it survives the hot, dry summer months by going dormant, waiting things out underground. Growth occurs in the cooler months, its bulb expanding annually before it finally flowers late one year after reaching at least 6 years old. Its flower stalk rises to as tall as 2 meters, extending heavenward from a bulb that can weigh as much as a kilogram. Its inflorescence is long, narrow, and loaded with small flowers that are generally white, but sometimes pink or red.

The oversized bulb of Urginea maritima — via wikimedia commons

Urginea maritima is commonly known as red squill or white squill (and sometimes simply, squill). Other common names include sea onion, sea squill, and giant squill. It is related the squill referred to in the Harry Potter universe, which is known botanically as Scilla. However, plants in the genus Scilla are much more dimunutive and generally flower in the spring rather than the fall. Like red squill, Scilla species are known to be poisonous; however, they don’t have the reputation for producing deadly rat poison that red squill does.

Like so many poisonous plants, red squill has a long history of being used medicinally to treat all sorts of ailments. As with any folk remedy or natural medicine, a doctor should be consulted before attempting to treat oneself or others. A 1995 report tells of a woman who ate red squill bulbs to treat her arthritic pain. She exhibited symptoms characteristic of ingesting cardiac glycosides – the toxic compound found in red squill – including nausea, vomiting, and seizures. She died 30 hours after eating the bulbs.

red squill (Urginea maritima) — via wikimedia commons

Toxic compounds are found throughout the plant, but are particularly concentrated in the bulb (especially its core) and the roots. Toxicity is at its highest during summer dormancy and when the plant is flowering and fruiting. The compound used to poison rats is called scilliroside. Bulbs are harvested in the summer, chopped up, and dried. The chips are then ground down to a powder and added to rat bait. Results are highly variable, so to increase its effectiveness, a concentrate can be made by isolating the toxic compound using solvents.

Red squill was introduced to southern California in the 1940’s as a potential agricultural crop. The region’s Mediterranean climate and the plant’s drought tolerance made it ideal for the area. The bulbs can be grown for manufacturing rat poison, and the flowers harvested for the cut flower industry. Breeding efforts have been made to produce highly toxic varieties of red squill for rat poison production.

the flowers of red squill (Urginea maritima) — via wikimedia commons

Around the time red squill was being evaluated as an agricultural crop, studies were done not only on its toxicity to rats, but to other animals as well. A 1949 article details trials of a red squill derived poison called Silmurine. It was fed to rats as well as a selection of farm animals.  Results of the study where “not wholly satisfactory” when it came to poisoning rats. Silmurine was less effective on Rattus rattus than it was on Rattus norvegicus. Thankfully, however, it was found to be relatively safe for the domestic animals it was administered to. Most puked it up or avoided it. Two humans accidentally became part of the study when they inadvertently inhaled the poison powder. Ten hours later they experienced headaches, vomiting, and diarrhea, “followed by lethargy and loss of appetite,” but “no prolonged effects.”

Vomiting is key. Ingesting scilliroside induces vomiting, which helps expel the poison. However, rodents can’t vomit (surprisingly), which is why the poison is generally effective on them.

Today, squill is available as an ornamental plant for the adventurous gardener. For more about that, check out this video featuring a squill farmer:

More Poisonous Plants posts on Awkward Botany:

Phylogenetic Arts and Crafts

This is a guest post by Rachel Rodman.


The foods we eat – namely fruits, vegetables, and grains – are all products of their own evolutionary stories. Some of the most well-known chapters in these stories are the most recent ones – dramatic changes in size and shape mediated by human selection.

One especially striking example is that of Brassica oleracea –the source of broccoli, cauliflower, kale, Brussels sprouts, kohlrabi, and cabbage. Each of these diverse vegetables belongs to the same species, and each is the product of a different kind of selection, exerted on different descendants of a common ancestor.

Corn is another famous chapter. The derivation of corn – with its thick cobs and juicy kernels developed from the ancestral grain teosinte, which it barely resembles – has been described as “arguably man’s first, and perhaps his greatest, feat of genetic engineering.”

But these, again, are recent chapters. Relatively. They unfolded over the course of consecutive human lifetimes –hundreds of years or thousands at the outset (sometimes much less). They are the final flourishes (for the moment) on a much older story — a story that significantly precedes agriculture as well as humans.

It is this older story that lies at the heart of truly deep differences, like those at play in the idiom “apples and oranges.” The contrast between these two fruits can be mapped according to many measures: taste, smell, texture, visual appearance, and so on. When used colloquially, the phrase serves as a proxy for unmanageable difference — to describe categories that differ along so many axes that they can no longer be meaningfully compared.

However, in evolutionary terms, the difference between apples and oranges is not ineffable. It is not a folksy aphorism or a Zen puzzle at which to throw up one’s hands. To the contrary, it can be temporalized and quantified; or at least estimated. In fact, in evolutionary terms, that difference comes down to about 100 million years. That is, at least, the date (give or take) when the last common ancestor of apples and oranges lived — a flowering plant from the mid-Cretaceous.

The best way to represent these deep stories is with a diagram called a phylogenetic tree. In a phylogenetic tree, each species is assigned its own line, and each of these lines is called a branch. Points at which two branches intersect represent the common ancestor of the species assigned to these branches.

Phylogenetic trees can serve many purposes. Their classical function is to communicate a hypothesis – a pattern of familial relationships supported by a particular set of data based on DNA sequence, fossils, or the physical characteristics of living organisms.

But here are two alternate reasons to build trees:

  • To inspire wonder
  • Or (my favorite) just because

To reflect these additional motivations – this conviction that trees are for everyone and for all occasions and that an evolutionary tree belongs on every street corner – when I build trees, I often avail myself of a range of non-traditional materials. I’ve written previously about creating edible trees using cake frosting and fruit, as well as building trees out of state symbols and popular songs. Now here are two additional building materials, which are arguably even more fun.

First: Stickers. This one is titled: “Like Apples and Oranges…and Bananas.”

Bananas split ways with the common ancestor of apples and oranges about 150 million years ago, 50 million years before the split between apples and oranges. On this tree, these relationships are represented like so: the banana branch diverges from the apple branch at a deeper position on the trunk, and the orange branch diverges from the apple branch at a shallower position. 

All of the data required to build this tree  (and essentially any tree) is available at TimeTree.orgOn TimeTree, select “Get Divergence Time For a Pair of Taxa” at the top of the page. This is where one can obtain a divergence time estimate for most pairs of species. The divergence time is an approximate date, millions of years ago, at which the organisms’ last common ancestors may have lived. For more heavy duty assistance, there is the “Load a List of Species” option at the bottom of the page. Here, one can upload a list of species names (.txt), and TimeTree will generate a complete tree – a schematic that can serve as a guide in patterning one’s own phylogenetic artwork.

Here, by way of additional illustration, are three more sticker trees, equally charming and equally mouthwatering:

Carrot, watermelon, broccoli, strawberry, and pear.

Onion, asparagus, tomato, cucumber, and cherry.

Raspberry, apricot, pea, grape, and green pepper.

Sticker trees are festive takes on traditional trees. They are brighter, livelier, and more lovely. But, like traditional trees, they are also 2D, restricted to a flat sheet of paper. To extend one’s phylogenetic art projects into three dimensions, one must modify the choice of materials. There are many options. The following 3D tree, for example, employs 13 pieces of plastic toy food, the accouterments of a typical play kitchen. Segments of yarn serve as branches.

Trees like these, made of stickers or toys, constitute playful takes on deep questions. In pencil and yarn, they sketch a network of primeval relationships. They tell the history of our foods, a narrative whose origins profoundly precede us, as well as our intention to selectively breed them. To the Way-Before, to the Way-Way-Way-Before, these projects give shape and color. If and where they succeed, it is because they manage to do two things at once: To communicate a vast biological saga extending across many millions of years, and to be completely cute. Perhaps best of all – and let it not go unmentioned – anyone can make them.


Bio: Rachel Rodman has a Ph.D. in Arabidopsis genetics and presently aspires to recast all of art, literature, and popular culture in the form of a phylogenetic tree.

Lettuce Gone Wild, part two

The lettuce we eat is a close relative to the lettuce we weed out of our gardens. Last week we discussed the potential that wild relatives may have for improving cultivated lettuce. But if wild lettuce can be crossed with cultivated lettuce to create new cultivars, can cultivated lettuce cross with wild lettuce to make it more weedy?

Because so many of our crops are closely related to some of the weeds found along with them or the plants growing in nearby natural areas, the creation of crop-wild hybrids has long been a concern. This concern is heightened in the age of transgenic crops (also known as GMOs), for fear that hybrids between weeds and such crops could create super weeds – fast spreading or highly adapted weeds resistant to traditional control methods such as certain herbicides. To reduce this risk, extensive research is necessary before such crops are released for commercial use.

flowers of prickly lettuce (Lactuca serriola)

There are no commercially available, genetically modified varieties of cultivated lettuce, so this is not a concern when it comes to crop-wild hybrids; however, due to how prevalent weedy species like prickly lettuce (Lactuca serriola) are, hybridization with cultivated lettuce is still a concern. So, it is important to understand what the consequences might be when hybridization occurs.

In a paper published in Journal of Applied Ecology in 2005, Hooftman et al. examined a group of second-generation hybrids (L. sativa x L. serriola), and found that the hybrids behaved and appeared very similarly to non-hybrid prickly lettuce. They also found that the seeds produced by the hybrids had a significantly higher germination rate than non-hybrid plants. This is an example of hybrid vigor. Thus, “if hybridization does occur, this could lead to better performing and thus potentially more invasive (hybrid) genotypes.” However, the authors cautioned that “better performing genotypes do not automatically result in higher invasiveness,” and that much depends on the conditions they are found in, the level of human disturbance, etc.

Another thing to consider is that hybrids are not stable. In an article published in Nature Reviews Genetics in 2003, Stewart et al. adress the “misunderstanding that can arise through the confusion of hybridization and … introgression.” It is wrong to assume that hybrids between crops and wild relatives will automatically lead to super weeds. For this to occur, repeated crosses with parental lines (also known as backcrossing) must occur, and “backcross generations to the wild relative must progress to the point at which the transgene [or other gene(s) in question] is incorporated into the genome of the wild relative.” That is what is meant by “introgression.” This may happen quickly or over many generations or it may never happen at all. Each case is different.

prickly leaf of prickly lettuce (Lactuca serriola)

In a paper published in Journal of Applied Ecology in 2007, Hooftman et al. observe the breakdown of crop-wild lettuce hybrids. They note that “fitness surplus through [hybrid vigor] will often be reduced over few generations,” which is what was seen in the hybrids they observed. One possible reason why this occurs is that lettuce is predominantly a self-crossing species; outcrossing is rare, occurring 1 – 5% of the time thanks to pollinating insects. But that doesn’t mean that a stable, aggressive genotype could never develop. Again, much depends on environmental conditions, as well as rates of outcrossing and other factors relating to population dynamics.

A significant expansion of prickly lettuce across parts of Europe led some to hypothesize that crop-wild hybrids were partly to blame. In a paper published in Molecular Ecology in 2012 Uwimana et al. ran population genetic analyses on extensive data sets to determine the role that hybridization had in the expansion. They concluded that, at a level of only 7% in wild habitats, crop-wild hybrids were not having a significant impact. They observed greater fitness in the hybrids, as has been observed in other studies (including the one above), but they acknowledged the instability of hybrids, especially in self-pollinating annuals like lettuce.

seed head of prickly lettuce (Lactuca serriola)

It is more likely that the expansion of prickly lettuce in Europe is due to “the expansion of favorable habitat as a result of climate warming and anthropogenic habitat disturbance and to seed dispersal because of transportation of goods.” Uwimana et al. did warn, however, that “the occurrence of 7% crop-wild hybrids among natural L. serriola populations is relatively high [for a predominantly self-pollinating species] and reveals a potential [for] transgene movement from crop to wild relatives [in] self-pollinating crops.”

Lettuce Gone Wild, part one

Lettuce, domesticated about six thousand years ago in a region referred to as the Fertile Crescent, bears little resemblance to its wild ancestors. Hundreds of years of cultivation and artificial selection eliminated spines from the leaves, reduced the latex content and bitter flavor, shortened stem internodes for a more compact, leafy plant, and increased seed size, among several other things. The resulting plant even has a different name, Lactuca sativa (in Latin, sativa means cultivated). However, cultivated lettuce remains closely related to its progenitors, with whom it can cross to produce wild-domestic hybrids. For this reason, there is great interest in the wild relatives of lettuce and the beneficial traits they offer.

image credit: wikimedia commons

Crop wild relatives are a hot topic these days. That’s because feeding a growing population in an increasingly globalized world with the threat of climate change looming requires creative strategies. Utilizing wild relatives of crops in breeding programs is a potential way to improve yields and address issues like pests and diseases, drought, and climate change. While this isn’t necessarily a new strategy, it is increasingly important as the loss of biodiversity around the globe threatens many crop wild relatives. Securing them now is imperative.

There are about 100 species in the genus Lactuca. Most of them are found in Asia and Africa, with the greatest diversity distributed across Southwest Asia and the Mediterranean Basin. The genus consists of annual, biennial, and perennial species, a few of which are shrubs or vines. Prickly lettuce (L. serriola), willowleaf lettuce (L. saligna), and bitter lettuce (L. virosa) are weedy species with a wide distribution outside of their native range. Prickly lettuce is particularly common in North America, occurring in the diverse habitats of urban areas, natural areas, and agricultural fields. It is also the species considered to be the main ancestor of today’s cultivated lettuce.

In a paper published in European Journal of Plant Pathology in 2014. Lebeda et al. discuss using wild relatives in lettuce breeding and list some of the known cultivars derived from crosses with wild species. They write that in the last thirty years, “significant progress has been made in germplasm enhancement and the introduction of novel traits in cultivated lettuce.” Traditionally, Lactuca serriola has been the primary source for novel traits, but breeders are increasingly looking to other species of wild lettuce.

bitter lettuce (Lactuca virosa) – image credit: wikimedia commons

Resistance to disease is one of the main aims of lettuce breeders. Resistance genes can be found among populations of cultivated lettuce, but as “extensive screening” for such genes leads to “diminishing returns in terms of new resistance,” breeders look to wild lettuce species as “sources of new beneficial alleles.” The problem is that there are large gaps in our knowledge when it comes to wild lettuce species and their interactions with pests and pathogens. Finding the genes we are looking for will require “screening large collections of well defined wild Lactuca germplasm.” But first we must develop such collections.

In a separate paper (published in Euphytica in 2009), Lebeda et al. discuss just how large the gaps in our understanding of the genus Lactuca are. Beginning with our present collections they found “serious taxonomic discrepancies” as well as significant redundancy and unnecessary duplicates in and among gene banks. They also pointed out that “over 90% of wild collections are represented by only three species” [the three weedy species named above], and they urged gene banks to “rapidly [acquire] lettuce progenitors and wild relatives from the probable center of origin of lettuce and from those areas with the highest genetic diversity of Lactuca species” as their potential for improving cultivated lettuce is too important to neglect.

Lactuca is a highly variable genus; species can differ substantially in their growth and phenology from individual to individual. Lebeda et al. write, “developmental stages of plants, as influenced through selective processes under the eco-geographic conditions where they evolved, can persist when plants are cultivated under common environmental conditions and may be fixed genetically.” For this reason it is important to collect numerous individuals of each species from across their entire range in order to obtain the broadest possible suite of traits to select from.

One such trait is root development and the related ability to access water and nutrients and tolerate drought. Through selection, cultivated lettuce has become a very shallow-rooted plant, reliant on regular irrigation and fertilizer applications. In an issue of Theoretical and Applied Genetics published in 2000, Johnson et al. demonstrate the potential that Lactuca serriola, with its deep taproot and ability to tolerate drought, has for developing lettuce cultivars that are more drought tolerant and more efficient at using soil nutrients.

willowleaf lettuce (Lactuca saligna) – image credit: wikimedia commons

Clearly we have long way to go in developing improved lettuce cultivars using wild relatives, but the potential is there. As Lebeda et al. write in the European Journal of Plant Pathology, “Lettuce is one of the main horticultural crops where a strategy of wild related germplasm exploitation and utilization in breeding programs is most commonly used with very high practical impact.”

Coming Up in Part Two: Can cultivated lettuce cross with wild lettuce to create super weeds?

What Is a Water Chestnut?

This question came up on a recent episode of Every Little Thing, and while I have eaten water chestnuts on numerous occasions, I realized that I have never really considered what they were or where they came from. Thanks to the folks at ELT, I am better informed. So, why not spread the wealth?

Chinese water chestnut (not to be confused with Trapa natans, which is also commonly known as water chestnut) is in the family Cyperaceae – the sedge family. Known botanically as Eleocharis dulcis, it is a member of a sizable genus collectively referred to as the spikerushes or spikesedges. Its distribution is quite expansive, spanning sections of Australia, tropical Africa, several countries in Asia, as well as islands in the Pacific and Indian oceans. It is commonly cultivated in regions outside of its native range, including in North America as a novelty crop.

Eleocharis dulcis is a perennial, aquatic plant that grows in marshes, bogs, and the margins of other wetland and riparian areas in tropical and subtropical climates. Individual plants are clumps of tall, stiff, upright, leafless stems that can grow to over one meter tall. An infloresence is borne at the tops of stems and is a short, cylindrical cluster of small, yellow-brown florets. Clumps of stems are connected via rhizomes, and in this manner dense colonies can be formed. Rhizomes also terminate in corms, which are the edible portion of E. dulcis and the part of the plant that we refer to as water chestnuts.

Chinese water chestnut (Eleocharis dulcis) growing in a bog garden – photo credit: flickr/techieoldfox

Corms are underground storage organs. They are the bases of stems that have become thick and swollen with starch. They are often covered in papery scales – which are the remnants of leaves – that help protect the corm from being damaged or drying out. Buds on the top of the corm form shoots; adventitious roots form on the bottom of the corm. Tubers, which are also modified stems and underground storage organs, differ from corms in that they have growing points at various locations along their surface rather than a single growing point at the top.

Common misconceptions are that water chestnuts are nuts or roots. They are neither. They are corms, or in other words, they are modified stem bases. Apart from that, they are vegetables. Curiously, they are vegetables from a plant family that does not produce much in the way of food for humans. Consider that the next time you eat them. You are eating a sedge.

Corm of Chinese water chestnut (Eleocharis dulcis), the edible portion of the plant – photo credit: flickr/sclereid0309

Chinese water chestnuts can be prepared in many ways, both raw and cooked. I have only had them in stir fries, but they can also be used in salads and soups or ground into flour to make water chestnut cakes. Interestingly, even when they are cooked they remain crisp. This has something to due with the special properties of their cell walls.

As an agricultural crop they are often grown in paddies in rotation with rice. With a few preparations they can also be grown at home alongside your other vegetables. Further information and instruction can be found at various locations online including Permaculture Research Institute, Missouri Botanical Garden, and Plants for a Future.

Having only eaten water chestnuts from a can, I am anxious to try fresh, raw water chestnuts. Apparently they are available at certain Asian markets. When I get my hands on some, I will let you know what I think. Follow me on Twitter or Facebook for further updates.


What are your favorite ways to eat Chinese water chestnuts? Let us know in the comment section below.

White Rot and the Quarantine Zone, revisited

This is a revised version of a post I wrote in July 2013 during the inaugural year of Awkward Botany.


It’s garlic planting season in the northern hemisphere. A few years ago, while helping out with the garlic harvest at a local farm, I had the chance to learn about some of the challenges involved in growing garlic in southern Idaho. Apart from the fact that it is a very labor intensive crop to grow, one of the major challenges stems from a disease called white rot – easily one of the worst diseases that garlic and onion growers face.

White rot is caused by a fungus (Sclerotium cepivorum), and it affects all plants in the Allium genus, including garlic, onions, chives, and ornamentals. The disease causes the leaves of alliums to die back, their bulbs to decay, and their roots to rot, ultimately turning the plants to mush. Sclerotia, the dormant stage of the fungus, are small (about the size of a poppy seed), black, spherical structures that can survive in soil for more than 20 years. They remain dormant until the exudates of allium plants awaken them, at which point they begin to grow, unleashing their destruction. Sclerotia can be moved around by farm equipment, floods, irrigation water, wind, and by attaching themselves to plant material. Once this fungus has established itself in a field, it is extremely difficult to eradicate, making the field virtually unfit for allium crops.

The threat of white rot and the monetary damage that it can cause led to the establishment of a quarantine zone in southern Idaho in order to protect its $55 million dollar a year onion industry. Due to the quarantine zone (which encompasses 21 counties), all garlic that is grown for seed within the zone must be inspected and certified. [“Seed” in this case refers to the garlic cloves themselves; onions, on the other hand, are grown from actual seeds and are not subject to the same protocol.] Any seed garlic that is brought into the zone must go through a rigorous testing process in order to ensure that it is free of the white rot pathogen before it can be planted. Garlic is a specific threat because the cloves can readily carry sclerotia, compared to onion seeds, which are not likely to harbor them.

This process significantly limits the amount and variety of garlic that can be grown in the quarantine zone. While the quarantine is essential for warding off the threat of this particular pathogen, it stifles the garlic growing industry and makes it difficult for new garlic growers to establish themselves.

Garlic farming is already incredibly demanding due to the amount of time and physical labor that goes into planting, harvesting, drying, grading, etc. The quarantine, while understandable, is an added challenge. Learn more about this issue by listening to this story on PRX.

See Also:

Garlic emerging in the spring.