Pollinators and vegetable gardens
Yesterday a reader asked if having a pollinator garden would help her vegetable garden. The answer to this is somewhat complex, depending on what you are trying to grow. There are general rules and exceptions.
If you are growing any kind of cucurbit—including melons, squash, cucumbers, zucchini, and gourds—pollinators are absolutely essential. Some are notoriously difficult to pollinate, especially pumpkins, which often require many pollinator visits before they will set fruit. Another completely pollinator-dependent garden crop is kiwi.
Blueberries, raspberries, blackberries and similar fruit will all do much, much better with bees. Although a few fruits may set without them, the yield would be greatly diminished. For the most part, the bean family is self-pollinating, but yields can be increased in the presence of bees.
There are a few crops, such as tomatoes, eggplants, and peppers that do fine outside without pollinators because the wind displaces the pollen from the anthers and disperses it. When raised in a greenhouse, however, these plants need pollinators to do the job of the wind. Certain bumble bees are raised specifically for use in greenhouse pollination of tomatoes.
In any plant where you eat the vegetative parts—such as broccoli, brussels sprouts, cabbage, carrots, cauliflower, collards, leeks, onions, potatoes, radish, or turnips—you don’t need pollinators. If, however, you want to save your own seed from any of these crops, then you do need pollinators. But again, the amount of gain from the pollinators depends on the individual crop. In this list, for example, lettuce is generally considered self-fertile and it will readily produce seed. Turnips, on the other hand, need pollinator assistance to produce a good crop of seeds.
It is interesting to note that two of our favorite tropical foods, chocolate and vanilla, are both completely pollinator dependent. Chocolate, Theobroma cacao, is pollinated by a type of midge, and vanilla, Vanilla planifolia, is pollinated by solitary bees.