Northern California writer Amy Stewart has written four books about plants — and none of them are your typical field book or gardening guide. Wicked Plants recounts the world's most dangerous flora, including the plant that poisoned Socrates. Flower Confidential exposes the bizarre engineering of the flower industry. Drunken Botanist, her latest, celebrates the plants that create well-loved drinks, from the juniper that adds floral notes to good gin to sorghum, perhaps the world's most widely fermented plant.
Stewart's roving curiosity and sense of delight make her a natural fit for Bastyr University's May 31 Herb and Food Fair, a garden party at our Kenmore campus that includes educational workshops, cooking demonstrations, herbal foot soaks, a craft sale, a plant sale, guided walks and much more. Stewart spoke with us in advance of her talk.
At Bastyr, we focus on a lot of health-giving plants in our botanical medicine programs. What inspired you to write about dangerous plants?
As I was doing research for Flower Confidential, I was talking to a lot of botanists. While touring a greenhouse, somebody said to me: “Come look at this thing I have growing in the corner. Don’t tell my boss I’m growing one of these.” It was actually on a university campus and the students thought they had gotten hold of Erythroxylum coca, the plant from the Andes that cocaine is made from. They were passing this plant around amongst themselves and chewing it. But it turned out to be a very caustic Euphorbia relative with a sap that could close your throat if you chew on it long enough.
That got me thinking there really are a lot of deadly and dangerous plants in the world. That’s how plants defend themselves. They can’t run away and hide. They can’t fight back. They don’t have opposable thumbs. But they can inflict pain and suffering on anyone who tries to eat them.
In a way it’s surprising that there are so many plants we can eat when you consider that it’s usually not in their best interest to be eaten, unless you’re a bird helping them spread seeds. So I thought it would be really interesting to tell that story. I wasn’t really interested in whether a plant could hurt someone, but who had it hurt? What specifically had happened? So that was how I cast my net, looking for plants that had been used as murder weapons or to start a war, or all the ways that those plants have intersected with our lives for the worse.
It sounds like a good way to appreciate the power of the natural world.
Right. And of course the line between medicine and poison is a very fine line. It’s all in the dose. A plant like foxglove gives us the medicine digitalis but can also be very dangerous. Caffeine is deadly in very high doses.
Let’s talk about the Drunken Botanist project. Why is it worth knowing what plants contribute to drinks?
When we talk about plants in alcoholic drinks, there are really three stages. There are the plants with enough sugar or starch to feed the yeast and produce alcohol — things like grapes, apples, rye and sugar cane. It's impossible to track all of them, because literally any fruit or grain on the planet has probably been fermented by somebody at some point.
Second, there are plants that might be added at the distillery or brewery to change the flavor. So hops in the case of beer or juniper in the case of gin. And third, plants that go into the glass to make some kind of drink. Those could be the ones we grow in our gardens: Mint, strawberries, blueberries and raspberries come to mind.
I have a garden of cocktail-friendly plants at home in Humboldt County, California. Some things that maybe don’t lend themselves very well to culinary uses are good in drinks, like scented geranium, lavender and lemon verbena, which pair very well in vodka or gin.
You can make great drinks that really let you appreciate those flavors. Alcohol is a solvent, so it extracts flavor and active ingredients from plants. That's why we started adding plants to alcohol — to preserve their medicinal qualities. A lot of cordials and aperitifs and old European liqueur like chartreuse started as medicine. Add a little sugar to get patients to take it and the modern cocktail is born.
There’s a lot of cultural anthropology in your work. Have you discovered practices from other cultures that Americans could benefit from adopting?
Well, I tried to be very careful about that. People always want to know if their favorite cocktail is a health drink and I’m always very quick to say let’s not fool ourselves. You’d poison yourself with the alcohol long before you’d ingest enough active medicinal ingredients to make a difference.
One exception to that, which I think I will talk about at Bastyr, is gentian. It's a plant found around the world, but there’s one species in the Swiss Alps that has been used as medicine for a long time. There’s some evidence that the amount of gentian that ends up in Campari or Angostura bitters has some medicinal qualities for digestion.
What’s going on in your garden this spring?
I’m growing black currant, which is something that people in the U.S. are not used to growing. In France, it's used to make cassis, a wonderful fruit liquor. It's used in kir, a classic drink with a little white wine and a splash of cassis. Black currants are very fun to grow in the Pacific Northwest. It’s one of those super fruits, very healthy.
I've got elderflowers as well. There’s a very popular elderflower liquor on the market right now, St. Germain. You can actually make your own if you can get enough elder flowers to bloom at once. I’m also trying to grow sloes, or blackthorn, Prunus spinosa, which is used to make sloe gin. That’s something that should do very well in the Pacific Northwest, but it turns out sloes are very slow to grow (ha ha). I’ve been growing them for several years now, and I have yet to get any fruit. I know the climate’s good for it, but I have not seen any fruit yet.