Added on May 31, 2014  Geoff McCabe

Toxic Edible Plants

It may sound like an oxymoron, but many plants that we have growing at the farm are highly toxic if the wrong part is eaten, if they’re eaten before they’re ripe, or uncooked, etc.

When giving tours of the farm, the guests sometimes freak me out by eating random stuff they find growing there! Let’s be clear: just because it’s natural, organic, and growing in nature, doesn’t mean it’s healthy. In fact, the vast majority of plants out there are toxic to humans. Many of them have dozens of toxic compounds that evolved in their systems to keep mammals from eating them.

Here’s a list of some of the dangerous plants that we can eat only if we know how:

Cashew:

Cashew trees grow very fast and we have several on the farm. Below the fruits, which look like a medium-sized bell pepper, is a shell which contains a syrup and a cashew seed. This syrup is highly toxic, and to make the cashews edible, they are cooked for quite a while in a high heat to boil off the urushiol poison. This is a tricky process that many of the local Ticos know how to do. Our volunteer coordinator, Joy Lopez, tried it with friends in another part of Costa Rica and they all got sick. As a result, the “raw cashews” you bought at Whole Foods probably aren’t.

Tomatillo:

We have wild tomatillo growing around the farm in random places. These small round fruits, surrounded by a paper “lantern” are toxic when they’re green. To eat them, you’ll need to let the paper shell dry out, leaving the tomatillos yellow and sweeter. Wherever we find them growing, we just leave them alone. Eventually the plant dries and collapses, and they continue to ripen on the ground for weeks. Eventually they’re yellow and ready to eat. They’re tasty, but not particularly sweet. If eaten when green, they’re mildly toxic, but not the type of thing that’s going to send someone to the hospital.

Tomato Leaves:

For years, tomato leaves have been known to be poisonous. I once read that assassins used to use them to murder people by slipping a few into their salad. Apparently, they could cause death by what appeared to be a natural heart attack. Other plants in the same Nighshade family are also toxic, such as eggplant, peppers, and potatoes. Sweet potatoes aren’t in this family so the leaves are fine (and very healthy) to eat. Some people cook with tomato leaves to enhance the flavor, which is apparently okay as long as you remove them and don’t actually eat them. Apparently the toxins stay inside the leaves during cooking/heating. Yet, this article claims that tomato-leaf toxicity is a myth, and not only that, but the leaves and green tomatoes have a great cancer-fighting chemical in them called tomatine. Read about that here: http://www.gardenbetty.com/2013/08/tomato-leaves-the-toxic-myth/

Yucca / Cassava:

This tasty root vegetable grows very well here in the beach climates of Costa Rica. However, you should never eat it raw! It has two types of cyanogenic glucosides, which convert to cyanide. This can be fatal or cause permanent paralysis. I have been told that some people are also slightly allergic to yucca and if eaten too frequently, they’ll start to go blind. Not eating it anymore will reverse the blindness. The more bitter the yucca, the more toxic it is, and when grown in drought conditions, it has even more toxicity.