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:

Advertisements

Podcast Review: Botanical Mystery Tour

My interest is piqued any time plants are featured or plugged in popular culture. Hence my ongoing series of posts, Botany in Popular Culture, featuring Futurama, Saga of the Swamp Thing, etc. Plants just don’t get enough airtime, so it must be celebrated when they do. Which is why I was excited to learn about Chicago Botanic Garden‘s new podcast, Botanical Mystery Tour, in which the plants referenced in pop culture take center stage.

The hosts, as they state in each episode’s introduction, “dive into the botany hidden in our favorite stories.” To help with the discussion, they bring in experts that work at Chicago Botanic Garden to explore the science (and fiction) behind the plant references. In addition to discussing pop culture and the related science, the guests share details about the work they do at the Garden and some of the research they are working on.

In the first episode, Jasmine and Erica ask Paul CaraDonna about the drone bees featured in an episode of Black Mirror. Since many bee species are in decline, will we have to resort to employing robot bees to pollinate plants that rely on bee-assisted pollination? A great discussion about native bees and colony collapse disorder ensues.

(But maybe the idea of autonomous drone insects isn’t too far-fetched…)

In episode two, the hosts ask why humans are so obsessed with corpse flowers. Thousands of people flock to botanical gardens to see these humongous, stinky flowers on the rare occasions they are in bloom, so what is so appealing about Amorphophallus titanum? Patti Vitt joins the discussion to share details about this fascinating plant.

A corpse flower in bloom is a brief and uncommon occurrence, reminiscent of the Sumatran Century Flower in The Simpsons and the 40 Year Orchid in Dennis the Menace.

 

The third episode features the sarlaccs of Star Wars. It turns out, sarlaccs are carnivorous plants. This discovery spawns an interesting discussion with horticulturist Tom Weaver about what defines a carnivorous plant and the various ways that different carnivorous plant species capture and kill their prey.

The fourth (and latest) episode is an exploration into the magical world of mushrooms. In Alice in Wonderland, Alice encounters a large, hookah-smoking caterpillar sitting atop a giant mushroom. Are there mushrooms big enough that a person could actually sit on them like Alice does? Greg Mueller joins the podcast to address this and many other mycology-based questions. The conversation includes a great discussion about why a botanical garden (whose main focus is plants) would be interested in fungus.

The discussions in this podcast are fun and enlightening. The hosts shine the spotlight on often overlooked characters in popular media, and with the help of their guests, lead captivating conversations about the science related to these characters. With only a handful of episodes available so far, it will be easy to get caught up. And then you, like me, will find yourself anxiously looking forward to embarking on another Botanical Mystery Tour.

———————

Is there a plant-themed podcast or podcast episode you would like to recommend? Please do so in the comment section below.

Seed Oddities: Vivipary

Seeds house and protect infant plants. When released from their parent plant, they commence a journey that, if successful, will bring them to a suitable location where they can take up residence (upon germination) and carry out a life similar to that of their parents. Their seed coats (and often – in the case of angiosperms – the fruits they were born in) help direct them and protect them in this journey. Physical and chemical factors inhibit them from germinating prematurely – a phenomenon known as dormancy. Agents of dispersal and mechanisms of dormancy allow seeds to travel through time and space — promises of new plants yet to be realized.

There is rarely a need for a seed to germinate immediately upon reaching maturity. In many cases, such as in temperate climates or in times of drought or low light, germinating too soon could be detrimental. The most vulnerable time in a plant’s life comes when it is a young seedling. Thus, finding the right time and space to get a good start is imperative.

The fruits (and accompanying seeds) of doubleclaw (Proboscidea parviflora) are well equipped for long distance dispersal. (via wikimedia commons)

In rare instances, dispersal via seeds offers little advantage; instead, dispersal of live seedlings or propagules is preferable. For this select group of plants, vivipary is part of the reproductive strategy. In vivipary, seeds lack dormancy. Rather than waiting to be dispersed before germinating, viviparous seeds germinate inside of fruits that are still attached to their parent plants.

Occasionally, seeds are observed germinating inside tomatoes, citrus, squash, and other fruits; however, these fruits are usually overripe and often detached from the plant. In these instances, what is referred to as “vivipary” is not a genetic predisposition or part of the reproductive strategy. It’s just happenstance – a fun anomaly. The type of vivipary discussed in this post is actually quite rare, occurring in only a handful of species and prevalent in a select number of environments.

There are three main types of vivipary: true vivipary, cryptovivipary, and pseudovivipary. In true vivipary, a seed germinates inside the fruit and pushes through the fruit wall before the fruit is released. In cryptovivipary, a seed germinates inside the fruit but remains inside until after the fruit drops or splits open. Pseudovivipary is the production of bulbils or plantlets in the flower head. It does not involve seeds and is, instead, a form of asexual reproduction that will be discussed in a future post.

True vivipary is commonly seen among plant communities located in shallow, marine habitats in tropical or subtropical regions, such as mangroves or seagrasses. The term mangrove is used generally to describe a community of plants found in coastal areas growing in saline or brackish water. It also refers more specifically to the small trees and shrubs found in such environments. While not all mangrove species are viviparous, many of them are.

Seedlings of viviparous mangrove species emerge from the fruit and drop from the plant into the salty water below. From there they have the potential to float long or short distances before taking root. They may land in the soil upright, but often, as the tide recedes, they find themselves lying horizontally on the soil. Luckily, they have the remarkable ability to take root and quickly stand themselves up. Doing this allows young plants to keep their “heads” above water as the tides return. It also helps protect the shoot tips from herbivory.

Viviparous seedlings emerging from the fruits of red mangrove (Rhizophora mangle) via wikimedia commons

Another example of vivipary is found in the epiphytic cactus (and close relative of tan hua), Epiphyllum phyllanthus. Commonly known as climbing cactus, this species was studied by researchers in Brazil who harvested fruits at various stages to observe the development of the viviparous seedlings. They then planted the seedlings on three different substrates to evaluate their survival and establishment.

Epiphyllum phyllanthus is cryptoviviparous, so the germinated seeds don’t leave the fruit until after it splits open. In a sense, the mother plant is caring for her offspring before sending them out into the world. The researchers see this as “a form of parental care with subsequent conspecific [belonging to the same species] nursing.” Since the plant is epiphytic – meaning that it grows on the surface of another plant rather than in the soil – local dispersal is important, since there is no guarantee that seeds or propagules dispersed away from the host plant will find another suitable site. That being said, the researchers believe that “vivipary involves adaptation to local dispersal,” since “the greater the dispersal distance is, the higher the risk and the lower the probability of optimal dispersion.”

Epiphyllum phyllanthus via Useful Tropical Plants

While some viviparous seedlings of mangroves can travel long distances from their parent plant and don’t always root into the ground immediately, they maintain their advantage over seeds because they can root in quickly upon reaching a suitable site and lift themselves up above rising tide waters. As the authors of the Epiphyllum study put it, vivipary is “a reproductive advantage that, in addition to allowing propagules to root and grow almost immediately, favors quick establishment whenever seedlings land on suitable substrates.”

There is still much to learn about this unusual and rare botanical feature. The research that does exist is relatively scant, so it will be interesting to see what more we can discover. For now, check out the following resources:

Also, check out this You Tube video of :

Seed Oddities: Apomixis and Polyembryony

Plants have uncanny ways of reproducing themselves that are unparalleled by most other living things. Offshoots of themselves can be made by sending out modified stems above or beneath the ground which develop roots and shoots (new plants) at various points along the way. Various other underground stem and root structures can also give rise to new plants. Small sections of root, stem, or leaf can, under the right conditions, push out new plantlets in a fashion that seems otherworldly. (Picture chopping off a bit of your finger and growing a whole new you from it.)

These are some of the ways in which plants reproduce asexually, and it’s kind of freaky if you think about it. Plants can clone themselves. But one major disadvantage of reproducing this way is that clonal offspring are genetically identical to the parent plant, which truncates any advantage that might be gained by genetic mixing between two separate plants. For one, it means that a plant population composed of all clones is at risk of being wiped out if something in the environment comes along (such as a disease or change in climate) and none of the plants in the population have adapted any sort of resistance to it.

New plants forming along the lateral stems of Ranunculus flammula – via wikimedia commons

That’s where seeds come in. Seeds are produced sexually, when the gametes of one plant fuse with the gametes of another. Genetic recombination occurs, and a genetically unique individual is born, housed within a seed. Unless, of course, that seed is produced asexually. Then the seed is a clone, and we’re back to where we started.

Apomixis is the process by which seeds are produced asexually. In flowering plants, this means that viable seeds are formed even when flowers haven’t been pollinated. In some cases, pollination stimulates apomixis or is required to produce endosperm; but either way, the result is the same: an embryo containing an exact copy of the genes of its single parent plant.

To understand this process, it’s important to familiarize yourself with the basic anatomy of an ovule, the part of a plant where embryos are formed and which ultimately becomes a seed. In gymnosperms, ovules sit inside cones; in angiosperms, they are surrounded by an ovary. The wall of the ovule is called an integument. A small opening at the top of the ovule, known as a micropyle, is where the pollen tube enters. Diploid cells of the nucellus compose the interior of the ovule, and within the nucellus resides the megasporocyte, which is where meiosis occurs and egg cells are produced. In sexual reproduction, a germ cell introduced through the pollen tube fuses with the egg cell to form a zygote and eventually an embryo. In the case of apomixis, the fusion of germ cells isn’t necessary for an embryo to form.

ovule anatomy via wikimedia commons

There are three main types of apomixis: diplospory, apospory, and adventitious embryony. In diplospory, the megasporocyte skips meiosis and produces diploid cells instead of haploid cells (germ cells). These unreduced cells go on to form an embryo inside of the embryo sac, just like an egg cell would if it had been fertilized with a pollen cell. Additional unreduced cells go on to form endosperm, and the ovule then matures into a seed. This type of apomixis is common in dandelions (Taraxacum officinale). As much as bees love visiting dandelion flowers, their pollination services are not required for the production of viable seeds. Yet another reason you are stuck with dandelions in your yard whether you like it or not.

In apospory, an embryo develops inside of an embryo sac that has been formed from cells in the nucellus. Embryo development within the megasporocyte is bypassed; however, pollination is usually necessary for endosperm to form. Plant species in the grass family commonly produce seeds using this type of apomixis.

Adventitous embryony is also known as sporophytic apomixis because an embryo is formed outside of an embryo sac. Cells from either the integument or the nucellus produce an embryo vegetatively. In this case, a sexually produced embryo can form along with several vegetatively produced embryos. Extra embryos die off and a single, surviving embryo is left inside the mature seed. But not always. Two or more embryos occasionally survive, including the sexually produced one. The mature seed then consists of multiple embryos. This phenomenon is called polyembryony and is common in citrus and mangoes. When it comes to plant breeding, polyembryony is incredibly useful because the asexually derived seedlings are exact copies of their parent, which means the desirable traits of a specific cultivar are retained.

Depiction of seed with three viable embryos after germination.

Polyembryony can occur in a number of ways, and not always as a result of apomixis. In some species, additional embryos “bud off” from the sexually produced embryo. This is called cleavage polyembryony and is known to happen frequently in the pine family (Pinaceae), as well as other plant families. Another common form of polyembryony in gymnosperms is simple polyembryony, in which several egg cells in a single ovule are fertilized resulting in the development of multiple embryos. This doesn’t always mean there will be multiple seedlings sprouting from a single seed. Most embryos usually fail to mature, and only one prevails. However, sometimes more than one survives, and if you’re lucky, you’ll find a seed with multiple plant babies pushing out from the seed coat.

Up Next: Vivipary!

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, documentariesarticles, 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 ThinkingErica 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:

Field Trip: UBC Botanical Garden and VanDusen Botanical Garden

Last week, we found ourselves in Vancouver, British Columbia for a work-related conference put on by American Public Gardens Association. In addition to learning heaps about plant collections and (among other things) the record keeping involved in maintaining such collections, we got a chance to visit two Vancouver botanical gardens. Both gardens were pretty big, so covering the entire area in the pace we generally like to go in the time that was allotted was simply not possible. Still, we were smitten by what we were able to see and would happily return given the chance. What follows are a few photos from each of the gardens.

UBC Botanical Garden

UBC Botanical Garden is located at the University of British Columbia. Established in 1916, it is Canada’s oldest university botanical garden. We saw a small fraction of the Asian Garden, which is expansive, and instead spent most of our time in other areas, including the Alpine Garden, the Carolinian Forest Garden, the Food Garden, and one of my favorite spots, the BC Rainforest Garden. The Rainforest Garden is a collection of plants native to British Columbia, which was the original focus of UBC Botanical Garden’s first director, John Davidson.

fall foliage of redvein enkianthus (Enkianthus campanulatus)

Franklin tree in bloom (Franklinia alatamaha) in the Carolinian Forest Garden

alpine troughs

bellflower smartweed (Aconogonon campanulatum)

cutleaf smooth sumac (Rhus glabra ‘Laciniata’) in the BC Rainforest Garden

the fruits of Gaultheria pumila in the E.H. Lohbrunner Alpine Garden

Himalayan blueberry (Vaccinium moupinense) in the E.H. Lohbrunner Alpine Garden

VanDusen Botanical Garden

VanDusen Botanical Garden is a 55 acre garden that opened in 1975 and is located on land that was once a golf course. It features an extensive collection of plants from around the world accompanied by a series of lakes and ponds as well as lots of other interesting features (like a Scottish Shelter, a Korean Pavilion, an Elizabethan Maze, and more). Our time there was far too brief. The whirlwind tour we joined, led by the education director, was a lot of fun, and if the threat of missing our bus wasn’t looming, we would have been happy to stay much longer.

Japanese anemone (Anemone x hybrida ‘Whirlwind’)

fall color on the shore of Heron Lake

knees of bald cypress (Taxodium distichum) in R. Roy Forster Cypress Pond

witch hazel (Hamamelis x intermedia ‘Pallida’)

a grove of giant redwoods (Sequoiadendron giganteum)

We tried the fruit of dead man’s fingers (Decaisnea insignis). It tastes a bit like watermelon.

Japanese stewartia (Stewartia pseudocamellia)

More Awkward Botany Field Trips:

How to Identify Puncture Vine (a.k.a. the Goathead Monster)

This post originally appeared on Idaho Botanical Garden’s blog. With the first annual Boise Goathead Fest fast approaching, the purpose of this post is to help people in the Treasure Valley identify goatheads so that they can collect them for drink tokens to use at the event. I’m reposting it here in hopes that people around the globe who are tormented by goatheads might benefit from it. All photos in this post were taken by Anna Lindquist.

———————

If you have spent much time on a bicycle in Boise, chances are you have been the victim of a goathead-induced flat tire. You probably even got a good look at the spiky nutlet as you went to remove it from your tire. But where did the culprit come from? No doubt, it came from a plant. But which one?

This is particularly useful to know right now because the first annual Boise Goathead Fest is coming up, and if you manage to fill a garbage bag full of these noxious weeds before the end of July, you will earn yourself a drink token. Fortunately, this plant is fairly easy to identify; however, there are a few look-a-likes, so it is important to familiarize yourself with the plant in question so you can be sure you are pulling the right one.

puncture vine (Tribulus terrestris)

Puncture vine, also known as goathead or Tribulus terrestris, is a warm season annual that is native to the Mediterranean region of southern Europe. It was introduced to North America unintentionally by early European settlers when the plant’s blasted burs snuck their way across the ocean in sheep wool. Since then, puncture vine has spread across the continent prolifically thanks to the hitchhiking prowess of its seeds.

Behold, the infamous Goathead Monster.

Puncture vine has a prostrate habit, meaning that its branches lie flat on the ground, spreading outward from a central location. It grows upward only when it is being shaded or crowded out. Its leaves are divided into several tiny leaflets, and its flowers are small and bright yellow with five petals. It is an otherwise pretty plant were it not for the threatening, jagged fruits that follow the flowers. As these fruits dry, they dislodge from the plant, split into five pieces, and lay in wait to puncture your tire, work their way into the bottom of your shoe or the foot of an animal, or latch onto some errant fur.

puncture vine (Tribulus terrestris)

Depending on the conditions, puncture vine either remains fairly small or spreads as much as six feet wide. Fruits start forming shortly after flowering, and seeds ripen soon after that, so if the plant isn’t removed quickly – nutlets and all – future populations are guaranteed. Luckily the plants are fairly easy to remove. Unless the ground is particularly compact, they pull up easily, and if they break off at the root, they generally don’t sprout back.

Virtually any plant that has a prostrate growth habit and is actively growing in the summer could, at first glance, be mistaken for puncture vine. Closer inspection will help confirm the plant’s true identity. Two plants that might confuse you are purslane and spotted spurge. Both of these species can be found growing in full sun in disturbed or neglected sites in close company with puncture vine.

Purslane has tiny, yellow, five-petaled flowers similar to puncture vine; however, its leaves are glossy and succulent-like and its stems and leaves often have a red to purple hue to them. Purslane seeds are miniscule, and while the plant can be a nuisance in a garden bed, it poses no threat to bicycles or wildlife.

purslane (Portulaca oleracea)

Spotted spurge, also known as prostrate spurge, can be quickly distinguished by the milky sap that oozes from its broken stems. Its leaves are generally reddish purple on the undersides with a purple spot on top. Its flowers are minute and its seeds even smaller. Because its sap contains latex and other chemicals, it can irritate the skin and poison creatures that dare eat it.

spotted spurge (Euphorbia maculata)

Both of these plants are introduced, weedy species, so even if they won’t count towards your drink token, it still doesn’t hurt to pull them. Puncture vine, however, is included on Idaho’s noxious weed list, which means it is particularly problematic. So take this opportunity to pull as many as you can, and hopefully we can put a sizeable dent in the population of a plant that has tormented Boise bicyclists for far too long.

See Also: Plant vs. Bike