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.

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

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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.

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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.

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Garlic emerging in the spring.

When Sunflowers Follow the Sun

Tropisms are widely studied biological phenomena that involve the growth of an organism in response to environmental stimuli. Phototropism is the growth and development of plants in response to light. Heliotropism, a specific form of phototropism, describes growth in response to the sun. Discussions of heliotropism frequently include sunflowers and their ability to “track the sun.” This conjures up images of a field of sunflowers in full bloom following the sun across the sky. However cool this might sound, it simply doesn’t happen. Young sunflowers, before they bloom, track the sun. At maturity and in bloom, the plants hold still.

What is happening in these plants is still pretty cool though, and a report published in an August 2016 issue of Science sheds some light on the heliotropic movements of young sunflowers. They begin the morning facing east. As the sun progresses across the sky, the plants follow, ending the evening facing west. Over night, they reorient themselves to face east again. As they reach maturity, this movement slows, and most of the flowers bloom facing east. Over a series of experiments, researchers were able to determine the cellular and genetic mechanisms involved in this spectacular instance of solar tracking.

Helianthus annuus (common sunflower) is a native of North America, sharing this distinction with dozens of other members of this recognizable genus. It is commonly cultivated for its edible seeds (and the oil produced from them) as well as for its ornamental value. It is a highly variable species and hybridizes readily. Wild populations often cross with cultivated ones, and in many instances the common sunflower is considered a pesky weed. Whether crop, wildflower, or weed, its phototropic movements are easy to detect, making it an excellent subject of study.

Researchers began by tying plants to stakes so that they couldn’t move. Other plants were grown in pots and turned to face west in the morning. The growth of these plants was significantly stunted compared to plants that were not manipulated in these ways, suggesting that solar tracking promotes growth.

The researchers wondered if a circadian system was involved in the movements, and so they took sunflowers that had been growing in pots in a field and placed them indoors beneath a fixed overhead light source. For several days, the plants continued their east to west and back again movements. Over time, the movements became less detectable. This and other experiments led the researchers to conclude that a “circadian clock guides solar tracking in sunflowers.”

Another series of experiments helped the researchers determine what was happening at a cellular level that was causing the eastern side of the stem to grow during the day and the western side to grow during the night. Gene expression and growth hormone levels differed on either side of the stem depending on what time of day it was. In an online article published by University of California Berkeley, Andy Fell summarizes the findings: “[T]here appear to be two growth mechanisms at work in the sunflower stem. The first sets a basic rate of growth for the plant, based on available light. The second, controlled by the circadian clock and influenced by the direction of light, causes the stem to grow more on one side than another, and therefore sway east to west during the day.”

The researchers observed that as the plants reach maturity, they move towards the west less and less. This results in most of the flowers opening in an eastward facing direction. This led them to ask if this behavior offers any sort of ecological advantage. Because flowers are warmer when they are facing the sun, they wondered if they might see an increase in pollinator visits during morning hours on flowers facing east versus those facing west. Indeed, they did: “pollinators visited east-facing heads fivefold more often than west-facing heads.” When west-facing flowers where warmed with a heater in the morning, they received more pollinator visits than west-facing flowers that were not artificially warmed, “albeit [still] fewer than east-facing flowers.” However, increased pollinator visits may be only part of the story, so further investigations are necessary.

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I’m writing a book about weeds, and you can help. For more information, check out my Weeds Poll.

Summer of Weeds: Lambsquarters

Since we seem to be on the topic of edible weeds we may as well discuss lambsquarters, another frequently present and commonly eaten, nutritious and versitile weed. Botanically known as Chenopodium album, it is a member of the family Amaranthaceae and therefore related to several common (and uncommon) agricultural crops, including spinach (Spinacia oleracea), beets (Beta vulgaris), Swiss chard (also Beta vulgaris), amaranth (Amaranthus spp.), and red orach (Atriplex hortensis). Chenopodium, a genus consisting of 100 plus species, is also cultivated in various parts of the world for its edible leaves, stems, and seeds. Chenopodium quinoa, commonly known as quinoa, is now a popular “grain” in North America after being grown for millenia by Andean cultures.

Chenopodium album is a summer annual that reaches up to 6 feet tall with sturdy, angular stems and triangular, diamond-shaped, or lance-shaped leaves with irregularly toothed margins. The leaves are green on top and mealy gray-white on bottom. The flowers are tiny, petal-less, and organized in tight clusters at the ends of branches. In Botany In a Day, Thomas Elpel describes the flowers as “little green ‘globs’ forming along an upright stalk, sometimes colored with specks of yellow.” They are generally wind-pollinated, but are occassionally visited by pollinating insects. Each plant can produce tens of thousands of seeds, which are potentially viable for up to 40 years.

Inflorescence of lambsquarters (Chenopodium album)

Lambsquartes is one of many common names for C. album (others include goosefoot, fat hen, baconweed, mealweed, frostblite, and wild spinach), and is a name with several proposed origins. Is it because the plant is commonly found growing in the manure-rich soils of barnyards? Or is it because the fuzzy undersides of the leaves are reminiscent of sheep’s wool? Perhaps it is because per weight, the harvested plants and a quarter of lamb contain roughly the same amount of protein? Who knows? Despite all this talk of sheep, however, large quantities of lambsquarters are reported to be poisonous to both sheep and pigs.

Though lambsquarters prefers nutrient-rich soils, it tolerates a wide variety of soil types, including dry, compacted, urban soil. It is drawn to all sorts of disturbed sites and is particularly abundant in gardens, agricultuaral fields, and roadsides. It readily hybridizes with other Chenopodium species, including the North American native C. berlandieri. In The Book of Field and Roadside, John Eastman calls it “one of the wold’s most abundant and noxious weeds,” because “it competes with some 40 crops [and] is especially invasive in tomato, potato, sugar beet, soybean, and corn fields.”

Eastman goes on to hint at lambsquarters’ potential for phytoremediation: “The plant accumulates high levels of nitrates and pesticides in addition to its oxalic acid content.” It also takes up heavy metals, including zinc, copper, and lead. This phenomenon is worth a future post, so stay tuned.

Leaf of lambsquarters (Chenopodium album)

That being said, when harvested from a non-polluted site, lambsquarters is a very nutritious spinach-like green both raw and cooked. Younger leaves and plants are preferred because older ones tend to be higher in oxalic acid. The seeds are also edible and, like quinoa, can be used in a similar manner as common grain and cereal crops. Harvester ants and various bird species also collect and consume the seeds. The roots of lambsquarters are high in saponin and can be used to make soap.

There are many reasons to be impressed with Chenopodium album, including its ability to tolerate drougt and frost, its adaptability to all types of soil, its highly nutritious plant parts (but also potentially toxic due to accumalation of pollutants and oxalic acid), and its competitive and persistent nature. Ehrenfried Pfeiffer, author of Weeds and What They Tell, was in awe of this “most enduring annual weed” and its goosefoot family relatives, writing: “We have the feeling that the goosefoot was destined to play a better role than to become an obnoxious weed. They follow closely man’s steps, showing their inclination to be domesticated. Probably future plant breeders may develop new cultivated varieties out of this family long after our present cultivated plants have degenerated, for it is their extreme vitality and preserverence to grow that makes the goosefoot family so interesting.”

Pfeiffer’s predictions haven’t quite come to pass, but time will tell.

More lambsquarters flowers

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According to an article posted on LiveScience, lambsquarters is one of “The Five Healthiest Backyard Weeds.” The list includes two other weeds we have covered during the Summer of Weeds: Purslane and Plantain.

Summer of Weeds: Eating Purslane

If it wasn’t so prolific and persistent, purslane would probably be a welcome guest in our vegetable gardens and edible landscapes. Easily among the most nutritious and versatile of the edible weeds, Portulaca oleracea is an annoyingly abundant annual that has inserted itself into garden beds and croplands in temperate climates across the globe. Thought to have originated in India or somewhere in Eurasia, purslane invaded North America long before Europeans did and has been naturalized across much of the continent for hundreds of years.

common purslane (Portulaca oleracea)

There are over 100 known species in the genus Portulaca, the only genus in the family Portulacaceae (otherwise known as the purslane family). Common purslane is a succulent plant with paddle- or teardrop-shaped leaves that generally grows low to the ground, forming a thick mat. It reaches for the sky when grown in shade or when competing with other plants for space. It produces little, yellow flowers that only open in bright sun and are typically self-pollinated. A small capsule containing dozens of tiny, black seeds quickly follows each flower. Each plant can produce tens of thousands of seeds, which remain viable for around 40 years.

Attempts to remove purslane by cultivation may only aid its survival. Broken pieces of the plant can take root in the soil, and uprooted plants can re-root if they are in contact with soil. Stirring up the ground brings to the surface seeds from purslane’s extensive seed bank. These freshly exposed seeds can then germinate, taking advantage of disturbance and open space. For all these reasons and more, John Eastman writes in The Book of Field and Roadside: “Purslane knows how to live and linger.”

The ever-urban and ever-common purslane.

The seeds of purslane germinate in late spring and throughout the summer when the soil has reached at least 75 – 80° Fahrenheit. It is adapted to high heat and dry soils. In order to conserve water, it switches to CAM photosynthesis when conditions are particularly hot and dry. In this photosynthetic pathway, carbon dioxide is stored as malic acid during the night and then converted back during the day. This means that, when it comes to eating purslane, the flavor changes depending on when the plant is harvested. In The Wild Wisdom of Weeds, Katrina Blair discusses this phenomenon: “In the morning purslane leaves contain as much as ten times more malic acid, making them very sour tasting. If you prefer a milder tasting purslane, harvest your greens in late afternoon and if you want more zing to your recipes, gather the leaves at dawn.”

Speaking of eating purslane, if all the claims are to be trusted, there may not be a more nutritious weed. In A Feast of Weeds, Luigi Ballerina calls it “a health bomb” because “it contains more omega-3 fatty acids than almost any other green, not to mention vitamins A, B, and C and beta carotene.” Blair calls it “one of the most nutritious plants on Earth,” and goes on to sing praises about its richness in dietary fiber, vitamins, minerals, protein, etc. Funnily enough, in describing the health benefits of purslane, Ballerina also quotes ancient sources claiming that “purslane calms sexual excitement.” Apparently it not only “eliminate[s] sensual dreams, but if used too much, it often extinguishes all ardor and even the capacity to procreate.”

With that caveat in mind, I tried it anyway. I had eaten it before, but nothing more than a leaf here and there and once in a green salad. I picked two recipes to try: Walnut Purslane Coleslaw from The Wild Wisdom of Weeds and Potatoes and Purslane from A Feast of Weeds. I’m generally a big fan of coleslaw, but for whatever reason I found this recipe to be a little bland. It was missing something, but I couldn’t put my finger on it. The purslane seemed to add a vague slimy-ness to it, which it will do on account of its mucilaginous nature.

Walnut Purslane Coleslaw

The Potatoes and Purslane recipe involved cooking the purslane. I enjoyed the finished product both hot and cold. The purslane added a sort of lemon-y spinach flavor. Those who tried it with me also liked it. The potato recipe was made with purslane that had been harvested in the morning, which may explain the strong lemon-y flavor. The coleslaw was made with purslane harvested in late afternoon, which may explain its blandness. I will have to try it the other way around for comparison. Purslane recipes abound in books and on the internet; browsing through them, I am intrigued enough to consider trying others. I think I’ll start with pickled purslane, purslane pesto, and perhaps, purslane sauerkraut.

Potatoes and Purslane

More Resources:

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Do you have a favorite purslane recipe? Share it in the comment section below.

Introducing the Summer of Weeds

I spent the first five months of this year posting almost exclusively about invasive species. There is still plenty more to say on the topic, and I’m sure I will get back to that. However, it is time now to dive into the topic that I really want to explore. Weeds.

There is definitely crossover between the two topics – many weeds are invasive species – but there are clear distinctions, too. Oftentimes, weeds as a category of plants are unfairly and unjustly lumped under the title “invasive,” but any plant can be a weed at any moment in time if a human says so. That’s the difference. A plant does not have to prove that it is causing any sort of ecological or economic damage to be called a “weed;” it just has to be growing where a human doesn’t want it to. Yet, too quickly a plant “out of place” is cursed at using words like “invasive” or “noxious” regardless of its origin or behavior. I know I’m being overly semantic about this, but it seems unfair (and incorrect) to lump any and all plants that are bothering us for whatever reason into categories that have legal definitions.

If you can’t already tell, I am obsessed with weeds. It’s a topic I have been thinking about fairly consistently for much of my adult life. For one thing, as part of my career I spend a huge portion of my time killing and controlling weeds. I comprehend fully the visceral reaction of seeing a garden overcome by weeds – the vile thoughts one can have towards a group of plants that are soiling what could otherwise be a beautiful landscape – and I know very well the backbreaking work and countless hours that go into removing uninvited plants (cursing the intruders along the way). I get why weeds are a problem, and I understand why they are a subject of so much vitriol. Yet, over the years I have developed a respect – even a love – for weeds (despite the fact that I still must remove them and that removing them continues to be an overwhelming task).

Unwanted plants have been following us around and getting in our way for millenia. Essentially, we are partners in crime. We intentionally and unintentionally bring plants from various parts of the world on our travels, and through disturbance we create conditions where introduced plants can settle in and thrive. Over time, some once beloved plants grow out of favor and transition from desirable to weedy. As our cycles of disturbance continue, we give early successional, opportunistic plant species a chance to perpetuate themselves, guaranteeing that we will keep such “weeds” with us forever. We reap what we sow; even though we generally don’t plant weeds on purpose, other actions ensure that they will be our constant companions.

The importance of weed control goes beyond the aesthetic. In horticulture and agriculture, weeds compete with crops for light, space, water, and nutrients. They also harbor pests and diseases, and their seeds can contaminate crops. In pastures and rangelands, some weeds poison livestock. Certain weeds are harmful to people, too. Other weeds are simply disruptive – getting tangled up in machinery, damaging infrastructure, blocking our vision along roadways, and even giving cyclists flat tires. Apart from all that, even if all weeds did was make our gardens look unsightly, I imagine we would still be pretty angry with them.

I am interested in weeds wherever they are, but the weeds that fascinate me the most are those that thrive in urban environments. Not necessarily the weeds in our yards, but the weeds that have escaped our fences and property lines; the ones in the margins. We see them in abandoned lots, along roadways, near irrigation channels, and in other neglected spaces. They pop up in the cracks of sidewalks, on rooftops, in the middle of decaying buildings, and anywhere else that people haven’t paid attention to in a while. Urban areas have, for the most part, been scraped of their native flora. Introduced species move in to fill that void. As Richard Mabey writes in his book about weeds, these plants “insinuate the idea of wild nature into places otherwise quite shorn of it;” they are “the very essence of wildness.” Novel ecosystems, like those created by urbanization and human development, are with us whether we like it or not. There is a “wildness” to them that is unlike other cultivated and manicured areas maintained by humans. These urban wild places are worth a closer look.

So, what is the Summer of Weeds?

Put simply, it’s an exploration of weeds. Throughout the summer I will be profiling some of the weeds I come across in my daily life. I will include photos, a brief description, and some interesting facts about each species. I will also include quotes about weeds from various sources, as well as videos, links, resources, and whatever else I come across that seems worth sharing. I hope you enjoy it. If you have anything to add along the way – specifically any personal thoughts or stories to share about weeds – please do. You can contact me via the usual ways: in the comment section below, through the Contact page, or on Twitter, Tumblr, Facebook, or Instagram. Happy Summer!

Poisonous Plants: Buttercups

Hold a buttercup flower under your chin. If your chin glows yellow, you love butter. That is according to a classic childhood game anyway. Recent research explored the cellular structure of buttercup petals and revealed the anatomical reason behind their yellow glow. Apart from helping to warm the flower’s sex organs, this glow is thought to draw in pollinating insects to ensure proper pollination.

Now take the fresh green leaves of buttercups, crush them up, and rub them against your skin. On second thought, DON’T DO THAT! This is not a childhood game and should absolutely be avoided…unless, of course, you derive some sort of pleasure from painful blisters.

Buttercups, also commonly known as crowfoots, are in the genus Ranunculus and the family Ranunculaceae. Ranunculus consists of a few hundred species and is a common group of annual and perennial herbaceous plants with alternately arranged, palmately veined leaves that are either entire, lobed, or finely divided. Buttercup flowers are usually yellow (sometimes white) with 5 petals (sometimes 3 or 7) that are either borne singly or in loose clusters. The flowers are complete, having both male and female reproductive structures that are easily identifiable. Flowering usually occurs in the spring.

bulbous buttercup (Ranunculus bulbosus) – photo credit: wikimedia commons

Ranunculus species are found throughout the world. Common habitats include moist woods, meadows, open fields, wetlands and other riparian areas, as well as drier sites like roadsides and neglected, urban lots. Several species are commonly grown as ornamentals, and others are common weeds in natural areas, urban landscapes, and agricultural fields.

All buttercups contain a compound called ranunculin. When the leaves are crushed or bruised, ranunculin breaks down to form an acrid, toxic oil called protoanemonin. Contact with this oil causes dermatitis. Symptoms occur within an hour of contact and include burning and itching along with rashes and blisters. When the leaves are chewed, blisters can form on the lips and face. If swallowed, severe gastrointestinal irritation can follow, accompanied by dizziness, spasms, and paralysis. The toxic oil is also irritating to the eyes.

Ranunculus species vary in their levels of this toxic compound, and individual plants are said to be more toxic in the spring when they are actively growing and flowering. Protoanemonin breaks down further into an innocuous compound called anemonin, so dead and dried out plants are generally safe. Commonly encountered (and particularly toxic) species in North America include tall buttercup (R. acris), cursed buttercup (R. sceleratus), creeping buttercup (R. repens), littleleaf buttercup (R. arbortivus), and sagebrush buttercup (R. glaberrimus). Bulbous buttercup (R. bulbosus) has bulbous roots that are toxic when fresh but are said to be edible after they are well boiled or completely dried.

cursed buttercup (Ranunculus sceleratus)

The toxicity of Ranunculus species seems to be more of an issue for livestock than for humans. Grazing animals tend to avoid it since it tastes so bad. Those that do eat it exhibit responses similar to humans – blistering around the mouth, gastrointestinal issues, etc. In The Book of Field and Roadside, John Eastman writes about Ranunculus acris: “Cattle usually avoid the plant – its acrid juices can blister their mouths – though they can also develop something like an addiction to it, consuming it until it kills them.” Buttercups becoming dominant in pastures and rangelands is often a sign of overgrazing.

Despite – and likely due to – their toxicity, buttercups have a long history of medicinal uses. Civilizations in many parts of the world have used the leaves and roots of the plant to treat numerous ailments including rheumatism, arthritis, cuts, bruises, and even hemorrhoids. A report published in 2011 describes three patients in Turkey that had applied poultices of corn buttercup (R. arvensis) to parts of their body to treat rheumatism. The patients were treated for chemical burns caused by the applications. The report concludes by advising against treatments “whose therapeutic effects have not been proven yet by scientific studies.”

In The North American Guide to Common Poisonous Plants and Mushrooms, buttercups are listed among plant species that are skin and eye irritants, honey poisons, and milk poisons (see Appendices 3, 4, and 5). Other genera in the buttercup family may also contain high levels of protoanemonin, including popular ornamentals like Clematis, Helleborus, Anemone, and Pulsatilla. Thus, the moral of this story: handle these plants with care.

sagebrush buttercup (Ranunculus glaberrimus)

More Poisonous Plant Posts on Awkward Botany: