Yew (Taxus spp.) is a good example of why eating samples of unknown plants is not always a safe practice. This shrub is commonly planted in front of houses, apartments, and businesses; however, nearly every part of the plant is extremely toxic. Just a few berries can lead to serious poisoning or even death. But don't let that scare you away from wild edibles! Yew is easy to differentiate from edible evergreens, as long as you pay attention to key identification features.
Before I go over the characteristics of yew, I would like to talk a bit about poisonous plants in general. After all, this is my first blog post that focuses entirely on a poisonous species!
The best way to avoid eating poisonous species is to learn which of them grow in your area, and what edible or medicinal species you might mistake them for. There are several books that list these species; for example, Peterson Field Guides has Venomous Animals and Poisonous Plants of North America and North of Mexico. Though by no means a definitive collection, it will help you avoid the most common toxic species.
Learning family characteristics also helps you avoid poisonous plants; Thomas Elpel's Botany in a Day is an excellent guide. This way, if you can't identify a plant, but can tell that it is part of the parsley family (for example), you may decide not to sample it because many poisonous species grow in that family, including two of the deadliest plants in North America-- poison hemlock (Conium maculatum) and water hemlock (Cicuta virosa).
Finally, any decent guide to edible or medicinal plants should go over poisonous look alikes. This is a good way to avoid specific toxic plants, but it will probably leave you in the dark about other dangerous plants growing in your area.
Habitat and Distribution
In the wild, the native Canada yew (Taxus canadensis) grows from Newfoundland and Labrador to western Ontario, southeast to West Virginia, and north along the Atlantic Coast. Pacific yew (T. brevifolia), also native, grows in Alaska, British Columbia and Alberta, southeast to Montana, southwest to Northern California, and back north up the Pacific Coast. The native Florida yew (T. floridana) is limited to Florida.
Yew grows in shady areas in moist forests. However— as previously stated— it is often used in landscaping. The most common ornamental varieties are European yew (T. baccata), Japanese yew (T. cuspidata), or a hybrid of the two (T. x media). Incidentally, these two are also the more toxic varieties! As an ornamental, it can be found far outside its wild range and habitat.
Canada yew is a midsize shrub, reaching heights of six feet. But what it lacks in height it makes up for in width; it can spread as wide as 100 feet through a process of clonal reproduction. Both Pacific yew and Florida yew grow much larger, reaching heights of 18 and 50 feet, respectively. However, they typically grow as tall understory shrubs. In an ornamental setting, yew is typically trimmed to heights of three to four feet, sometimes into neat rectangular shapes.
As an evergreen species, yew has needle-like leaves that persist for about two years. They grow singly, are arranged in two lateral rows along the branch, are 1/2 to 1 inch in length, flat-shaped, and have sharp, pointed tips.
Yew produces red arils— berry-like seed coverings. (I'll just call them "berries" for simplicity's sake.) They are fleshy, cup-shaped, and 1/4 to 1/2 inch long. The inside of the cup houses the brown seed, which is less than 1/4 inch in diameter. This reproductive structure is unique to yew; most evergreens produce seed cones. If you find an evergreen with small red, fleshy berries, it is certainly yew. However, the berries typically mature from June to September, so they're not a reliable identification mark year-round. You should also be aware that yew (like other evergreens) produces strobili, which are not the same as mature seed cones! Strobili are cones (about 1/8 inch long in the case of yew) that produce pollen and/or ovules, depending on the sex. In yew, male and female strobili grow separately; the male strobili pollinate the female, which eventually mature into arils (berries). It's unlikely that you would mistake them for mature seed cones since they're so tiny and inconspicuous; but I just don't want you to notice them and mistakenly think that the plant is producing seed cones and not berries, so it must not be yew.
Edible Look Alikes
Other needle-bearing trees could be mistaken for yew, but of those, firs (Abies spp.) are the most probable. Like yew, firs have single flat-shaped needles that are arranged in two lateral rows on the branch. Unlike yew, the needles are blunt-tipped or notched. Furthermore, firs are trees— not shrubs— so they grow much taller than yew (reaching heights of 85 feet) and have a single trunk with resin-filled pockets. The overall shape of the tree is sharply triangular.
Common juniper (Juniperus communis) is a spreading shrub with sharp-pointed needles that grow in whorls of three. (Those of yew grow in two rows.) Furthermore, juniper produces dry, blue berries, unlike the red, fleshy berries of yew.
Eastern hemlock (Tsuga canadensis)— the tree, not the poisonous plant— also has single flat-shaped needles that are arranged in two lateral rows on the branch. However, the needles are much smaller at 1/4 to 1/2 inches and they are blunt-tipped. Eastern hemlock is a tall tree, reaching heights of 100 feet.
Pines (Pinus spp.) and tamaracks (Larix spp.) have needles that grow in bunches, unlike yew, whose needles grow singly. Spruces (Picea spp.) have sharp needles that are roughly square-shaped in cross-section, unlike yew's flat needles. Furthermore, they are spirally arranged on the branch, not in two rows.
All parts of yew are deadly poisonous, except for the flesh of the berry. However, the seed within is the most poisonous part of the plant! Therefore, I don't recommend popping the berry in your mouth and spitting out the seed. It's just too risky! I had a friend who would do this solely to freak me out. He's dead now. Just kidding! But seriously, don't do it.
If you're so very curious about the flavor of the flesh of the berry that you can't even contain yourself, here's what you can do: pick a berry from a shrub, remove the seed by hand, put the fleshy part in your mouth, and discard the seed. I promise you, it's not worth the effort. Imagine a tiny, watery strawberry with no flavor, and you'd be pretty close to the taste of yew berries. I wouldn't eat it unless it was a survival situation and I had literally nothing else to eat. Which seems like a pretty unlikely scenario.
So what makes yew so poisonous? It contains a deadly alkaloid called taxine. This is a rapidly absorbed cardio-depressant that can kill within a few hours of ingestion in cases of acute poisoning, but may take as long as 24 to 48 hours if smaller amounts were consumed. Oftentimes there are no symptoms until the heart suddenly stops. If there are symptoms, they may include trembling, staggering, nervousness, coldness, weakness, vomiting, and low blood pressure.
It's not just toxic to humans, either; yew is a well-documented killer of livestock, including cattle, horses, goats, and sheep. Typically they don't consume yew unless they're low on forage. There is some evidence that white-tailed deer are resistant to the yew toxin; however, articles indicate that not all deer species are resistant. There is at least one report of a moose dying of acute yew poisoning.
Interestingly, taxine does not disperse after parts of the shrub are cut. Thus, yew trimmings retain their poison until they compost entirely. This is also true of the seeds and roots. Even the pollen contains taxine! However, it is in far lower concentrations than other parts of the plant. Some sources claim that yew pollen can cause lethargy, headaches, aching joints, and rashes. However, this may stem from the Ancient Greek doctor Dioscorides, who asserted that yew emits poisonous fumes, and that sleeping or eating under it can cause death. I wasn't able to find any scholarly articles to substantiate claims that yew pollen is anymore harmful to humans than other pollen.
However, it's not all bad news. Researchers developed a potent anti-cancer drug from the bark of Pacific yew. Called paclitaxel, this compound blocks cancer cell growth by halting cell division. It is the most popular naturally-sourced cancer drug in the US to date, used for ovarian and breast cancer.
For all it's poisonous properties, yew is still a beautiful ornamental. With its evergreen needles and bright red berries, it's easy to see why this plant is so popular in landscaping. Just don't eat it! Or sleep under it, if you happen to be an ancient Greek physician.