In one of my first small gardens, I planted a pumpkin plant and a zucchini plant next to each other. I didn’t save any of their seeds, but the next year, when I spotted a pumpkin plant coming up from the compost, I let it grow. It started out looking like a bit like an elongated pumpkin or some sort of squash. Then it ripened to the above specimen, which was christened the zupumpkin.
Cross-pollination occurs when an insect or the wind carries pollen from one variety of plant to another. The resulting seed, when planted, sprouts a hybrid of its parents. Since zucchini and pumpkins are both varieties of the same species, they can create the zupumkin (or zumption or pumcchini–your choice) but a cucumber and squash can’t procreate because they’re different species.
Cross-pollination does not affect the current year’s crop, but rather the next year–with one exception: corn. If the pollen from the tassels of one variety of corn are blown into the silks from another variety, the cob that develops is a hybrid.
Vegetables like beans, peas, peanuts, eggplant, peppers, lettuce, and tomatoes are self-pollinating. Their seeds will produce plants like the parent, but insects will occasionally cross them, so if you want to be absolutely certain that your seeds will grow true to type, plant each variety at least 10 feet apart.
Insect- and wind-pollinated plants
Vegetables that are pollinated by insects or wind need to be separated by variety, and grown a distance apart (the distance varies with each type of plant). To ensure that your seeds grow true to type, grow one variety of each type, or separate the different varieties.
Vegetables that willingly cross-breed
The following plants or plant families are prone to cross-pollination. If you are planting them with the intention of keeping their seeds, keep varieties well separated.
- Beets and Swiss chard
- Cauliflower, cabbage, kale, Brussels sprouts, kale, collard greens, and broccoli
- Honeydew, cantaloupe, and other melons, excluding watermelons
- Peppers (hot and sweet)
- Squash (some varieties)
- Zucchini and pumpkins