Gardening is like anything else. Fads, rumors, trends, and shared concerns spread through the community from time to time. In a way, this is a great sign; it shows that gardeners talk to each other and that there’s a genuine community around growing and caring for plants. While some of the fads can be questionable, our shared questions and concerns are a chance to learn and to share good information with others. We recently came across one such question/concern: are volunteer squash toxic? Many of us, especially those who compost, have had “volunteers” (plants that grow from a seed planted unintentionally) pop up in our garden spaces. There’s a worry now that volunteer squash seeds can be toxic. But is it true? Let’s dig in and learn more about volunteer squash, squash toxicity, and how to ensure we’re harvesting safe-to-eat vegetables.
Gardzen Executive Summary:
· Volunteers can be problematic. Due to cross-pollination they may not breed “true to type” and might produce low-quality or inedible fruit.
· Whether volunteer or deliberately planted, sometimes squash, cucumber, zucchini, or pumpkin plants will produce bitter-tasting fruit. Please note that this is relative to a normal fruit in the varietal—some are meant to be bitter in flavor!
· These overly-bitter fruits can cause stomach upset or digestive distress, so don’t eat them. Sample a small piece of garden fruits first to ensure they’re good.
· However, we can’t find any evidence that volunteer squash are toxic. As far as we know, volunteers are safe to eat.
Cucurbitaceae, Volunteers, and Bitter Fruit
While we think of squash, zucchini, pumpkins, and cucumbers as distinct plants, they are all related in that they’re all members of the family cucurbitaceae. Due to their shared heritage and DNA, all of these plants contain substances called cucurbitacins, albeit to varying degrees. Cucurbitacins give the fruits of cultivated varieties a mildly bitter flavor, which can be either negligible or even pleasant for those of us who enjoy eating them.
Cucurbitacins are safe to eat in the low concentrations we find in garden veggies. Every now and then, however, cucurbitaceae plants produce fruit that have especially high concentrations of cucurbitacins, giving that fruit a bitter and unpleasant flavor. This is a good thing, as consuming fruit with too much cucurbitacins can cause stomach pain and diarrhea in humans and animals.
These bitter fruits can occur for a variety of reasons. If cucurbitaceae plants don’t get good, consistent watering, the fruit can become bitter on the vine. Fluctuations in temperature or overly-hot temperatures can do the same thing under some circumstances. Another possible source of problems comes from cross-pollination. The fruit of cross-pollinated cucurbitaceae seeds may not breed true to type, and may produce misshapen, woody-textured, or bitter tasting fruit. The concerns about volunteer squash start here: they may be cross-pollinated and produce fruit that causes digestive issues in those who do eat them.
So we know that under some circumstances cucumbers, squash, pumpkins, zucchini and the like can produce fruit that’s not good to eat, and we know how to spot them via an especially bitter flavor. It’s a good idea to cut a small sliver of our cucurbitaceae as a taste-test before we start cooking just to ensure everything’s OK—especially if the fruit is weirdly-shaped or colored! But let’s get back to our central question: are volunteer squash, cucumbers, etc more likely to be toxic? The explanation gets a little complicated, but fortunately the answer is simple . . .
Are Volunteer Squash Safe to Eat?
The short answer is: yes. As far as we know cucurbitaceae volunteers will generally be safe to eat pending the taste test we should apply to all squash, cucumbers, etc just to be safe. Volunteers will not be dangerous to eat in and of themselves, and the worst that will happen if we force ourselves to eat an unusually bitter squash or cucumber is a stomachache and some extra time in the bathroom.
How likely is that to happen? Well, even if we ignore the warning from our taste buds the likely of bitterness and a high cucurbitacins concentration in a volunteer is the same as in any other cucurbitaceae. If the plant has bred true to type and has had appropriate water, sun, and temperature conditions then the fruit will likely be good to eat. Volunteers from home-grown plants are more likely to cross-pollinate and not run true to type, but that will likely result in misshapen or malformed fruits, bitter flavors, and woody textures too.
Should We Let Volunteers Grow in Our Gardens?
The short answer to this one is . . . maybe? We’ve been known to let some volunteers stick around, especially those from self-fertilizing plants like tomatoes. They’re free seedlings and it’s kind of fun to see them pop up like a surprise gift. With plants that are prone to cross-pollination—cucurbitaceae, for example—we’re a bit more cautious. On the one hand this is how new varieties are born, but we don’t know what a volunteer will give us. It could be a brand new breed of squash, or cucumber, or whatever else. It could be a “normal” fruit and some free seedlings. Or it could be a cross-pollinated plant that doesn’t give us anything usable. So it all comes down to how much garden space we have and how adventurous or experimental we’re feeling.
Volunteers are a reminder that plants and seeds are living things, and that life will find a way to survive and thrive. While gardens are an attempt to grow plants in a controlled way, nature will always have surprises for us, among which are volunteers. So while volunteer squash aren’t toxic, they are a reminder of the wild nature of plants and gardening and (potentially) a chance to try out something new.
Just don’t eat squash that taste too bitter.
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