I have a farmers’ market friend who calls her volunteer squash “garden whimsy.” This time of year, when I see a random squash plant pop up in our compost pile, I think of her and smile. While their appearance is a fun surprise, an important question to ask is whether volunteer squash are safe to eat.
Many gardeners will tell you that the best squash they’ve ever eaten was from a volunteer plant. One of our favorites from a few years back looked like a mix between a yellow summer squash and a ‘Carnival’ winter variety. It had a lovely, smooth, tan interior flesh perfect for roasting. However, it doesn’t always turn out that way.
Let’s talk about how to know if these misfits are safe to eat or if we should let them be.
The Short Answer
The short answer is that volunteer squash may be safe to eat, but they might not be! Eat them only at your own risk. Thankfully, there’s a simple test that helps you determine which ones are likely safe to consume and which are not, and some methods you can use to decrease their occurrence.
The Long Answer
Over millennia, squash evolved from inedible forms, changing in flavor, size, and bitterness.
Thousands of years ago, squash was inedible to humans. Since then, it has gone through many versions of itself, ranging in flavor, use, size, shape, bitterness, and flavor. Humans have bitterness receptors that tell them which foods may not be safe for consumption, and this garden fruit runs the gamut on bitterness levels.
Some foods contain a compound called cucurbitacin that’s safe to eat at normal levels. However, these levels increase under certain conditions, resulting in toxic food.
A Brief History of Wild Squash Evolution
This crop was once inedible to humans.
Historians believe that squash has been domesticated about six different times globally. Humans initially did not consume it but rather used it as a tool or container because of its bitter flavor.
However, large mastodons that roamed during the Pleistocene epoch had fewer bitterness receptors. They could crush the hard exteriors and get to the nutritious center. They spread the seeds and gave squash a chance to continue evolving, making these creatures a huge part of this crop’s survival.
Fun fact: The seeds that humans brought to the Americas did go extinct in their native habitat due to climate change and the overhunting of wild animals who spread their seeds. This means the pumpkins you know today have genes of Cucurbita cultivated by humans about 10,000 years ago.
What Is A Volunteer?
Squash can sprout from discarded seeds in your compost pile.
A volunteer is a term used for squash, melon, or pumpkins whose seed germinated after being discarded into a compost pile, dropped from a fruit, or carried away and buried by a bird or critter. Basically, it’s a plant that showed up where you didn’t intentionally plant it.
It’s probably no shock to home gardeners to notice a random pumpkin plant emerging from the compost pile. Sometimes, these contain fruit; other times, they’re mostly vine.
Something about life being created out of death is soothing to me, so I generally leave them be, watching curiously to see what type of fruit will set. The jury on whether this squash was cross-pollinated during the previous season will be out until the fruit matures.
Cross-Pollination
Identification is challenging until maturity.
Cross-pollination occurs when pollen from a male flower of one type of squash is transferred to the female flower of another type. The current season’s fruit is produced from the female flower’s ovule and will not be altered even if the pollen from the male is a different variety.
However, the resulting seed inside the fruit may contain male and female genes and express aspects of each. The plant that grows from it will be a mix of the two plant parents.
Fun fact: The process above is how new cultivars are created!
How Cross-Pollination Works
Squash refers to summer squash, zucchini, winter squash, pumpkins, melons, and other gourds. They are all in the same plant family, Cucurbitaceae, and are unisexual. This means they contain both male and female flowers. They require a pollinating insect to come along and transfer pollen from one flower to the other to form fruit.
For this reason, cross-pollination is common, especially in garden plots where several different varieties of cucurbits are being grown. Anyone who saves seeds has likely planted what they thought was zucchini that turned out to be “garden whimsy.”
When seeds are dispersed from discarded plants or moved by a critter, new plants can easily germinate. When fruit from the plant starts to mature, you may notice it looks different from others you’ve seen before. It’s almost a guarantee it won’t be the variety you picked from the seed catalog.
Remember, one parent could be a winter squash, and the other could be a summer squash. The fruit’s exterior may look like either, and you won’t know what’s inside until you cut it open!
Pro tip: If the exterior of a volunteer looks like a gourd, try curing it for fall décor!
Varieties That Can Cross-Pollinate
Cross-pollination for these plants only occurs within the same species, not between different species like cucumbers.
So this is where it gets interesting. Not all squash can scientifically cross-pollinate, only those within the same species, which should ease your gardening heart a little.
Cross-pollination can happen if you have any pairing from the following groups in a small space:
- Members of Cucurbita pepo: Zucchini, Yellow Crookneck, Acorn, Spaghetti, Patty Pan, Delicata, various pumpkins, and gourds
- Members of Cucurbita maxima: Butternut, Buttercup, Banana, Hubbard, and Turban
- Members of Cucumis melo: Muskmelon (aka cantaloupe), Charentais (French cantaloupe), honeydew, Casaba (winter melon), Armenian Cucumber; Snake melon
Although squash is in the same family as cucumbers (Cucurbitaceae), cross-pollination between the two species is impossible.
How to Prevent Cross-Pollination For Saving Seeds
It’s hard to avoid cross-pollination in a home garden.
Typically, a half mile to a mile is the distance between crops in the same family that can reduce the risk of cross-pollination. However, not many of us have that luxury!
The best approach is to grow a few varieties and hope for the best. Cross-pollination, theoretically, is quite rare. But if you want to get serious about saving seeds and ensure their genes are pure, follow these tips.
How To Hand-Pollinate
Cover plants with insect netting or tape flowers before they open to prevent cross-pollination.
- Cover your plants with insect netting to create a barrier that will keep pollinating insects out. Alternatively, you can tape flowers to prevent them from opening. Do this when the flowers are still mostly green and stiff, showing a bit of orange coloring. Once open, insects will pollinate; in this case, we want to avoid this.
- Early morning, before insects are out and about, take a small, clean paintbrush to your squash patch and uncover or un-tape your patch.
- Dab the paintbrush inside the male flower to remove some pollen.
- Transfer pollen to the stigma (the round, sticky, yellow piece in the middle, resembling a bulb) in the female flower. This is best if done soon after the female flower opens in the morning (four hours or less). The humidity is highest, which helps the pollen stick.
- Pull the insect netting back over your patch or re-tape the flowers shut.
Repeat this a few times a week or daily if you’d like. You can remove the insect netting or bags once you see that the fruit has set. Mark your plants so that you know which ones were pollinated by hand. The seeds from these will stay true to the parent plant.
The female flower is the one that forms the fruit. Identify it by the swelling at the base before the fruit forms. The “showy” male flower has a pollen-filled stamen in the center. You may notice more male flowers due to their critical role in pollination.
Wait until your squash is almost over-ripe before harvesting for seed-saving. This will ensure proper seed maturity.
What Makes Volunteer Squash Potentially Dangerous
Cucurbit family plants contain cucurbitacin, a compound that can make squash bitter.
As I briefly mentioned above, the cucurbit family contains a compound called cucurbitacin. In cultivated varieties, mammals rarely detect very low levels of cucurbitacin.
However, if squash plants are under stress, the level of cucurbitacin may be much higher, making the bitterness more obvious and sounding the safety alarms. Our ability to sense and react to bitterness is an adaptation that keeps us safe.
What Causes Cucurbitacin to Increase?
Adverse conditions like drought or extreme weather can raise cucurbitacin levels, leading to bitterness.
Like many other crops, strange things can happen when plants are under stressful conditions. In cases of prolonged drought, poor pollination, or extreme rain, plants will go into a high-stress state, and regular activities such as pollination, normal growth habits, and reproduction will be affected.
When growing conditions are less than ideal, cucurbitacin levels may increase, causing bitterness. This includes drought conditions, prolonged heat or cold, heavy rainfall, improper spacing or fertility, or even lack of space.
How To Test Volunteer Squash For Safe Consumption
Do a taste test but monitor for symptoms after consumption, and seek medical help if needed.
If you want to know if your volunteer is edible, take a sample fruit and cut a small slice with a clean knife. Then, place it on your tongue for several seconds, noticing any bitterness coming through. If it is bitter, remove the fruit immediately, and do NOT consume the squash. If you do not taste any bitterness, you may choose to eat it, but do so at your own risk!
Seek medical attention if you have any questionable symptoms after consuming, even if it tasted normal.
Toxic Squash Syndrome
Consuming too much cucurbitacin can lead to illness.
If someone eats too much squash that’s high in cucurbitacin, they may become ill. Symptoms include vomiting, diarrhea, and abdominal pain. Extreme cases, although rare, can cause swelling of the liver, gallbladder, kidney, and pancreas.
If you have recently eaten a volunteer and think you are showing signs of toxic squash syndrome, seek a doctor’s assistance immediately.
Illness and death caused by cucurbitacin toxicity are incredibly rare because humans typically stop eating something that tastes bitter, especially if it’s something that doesn’t usually taste this way.
Final Thoughts
Cross-pollinated squash plants can create funky-looking fruits, great for displays, ornamental gardens, or experimental side dishes. But beware. High levels of cucurbitacin can cause bitterness in fruits and Toxic Squash Syndrome, leading to discomfort and, in very rare cases, death. If you choose to consume your volunteer squash, do the bitterness test first. Then, eat at your own risk.
