by Eric Solderholm, CFSA’s Organic Transition Coordinator.
Squash season is upon us and with it come a number of challenges for raising a healthy, productive crop. One of these is pollination. Plants that are members of the cucurbit family (summer squash, winter squash, pumpkins, melons, cucumbers) produce unisexual flowers and must have pollen moved from male flowers to female flowers to set a viable fruit. Female flowers that have not been pollinated will still produce a fruit, though it is often significantly smaller, shriveled, misshapen and doesn’t have seeds. Not an attractive sight on any farmers’ market table! There are several insects that serve as pollinators in a squash patch, and it is beautiful to observe their activity when crops are in full bloom. Honeybees can play an important role is pollination, but they aren’t the only ones on the scene.
Squash are native to the Americas and their domestication by American Indian farmers predates maize. The squash bee (Peponapis pruinosa) is also a native to North America, unlike the honeybee. For the casual observer, they are difficult to tell apart from honeybees. But get down on your belly to check out several striking difference. The squash bee has much more distinct light colored stripes on its abdomen and has combs, rather than a “pollen basket,” on its hind legs for carrying pollen. Click here to see some images of this striking bee.
This species has developed a unique symbiotic relationship with squash, feeding exclusively on the pollen of the cucurbit family. They are considered extremely effective pollinators. As specialists, they make more contact with reproductive structures in the flower, start earlier in the morning and move rapidly from flower to flower without deviating to other plant species. These bees are solitary, live in nests in the soils and produce one generation each year. I have often caught them mating in squash flowers and males will overnight in the closed blooms, ready to get back to work in the morning. To encourage squash bees in your garden, it is best to avoid deep tillage. There have been many mornings when I have seen squash bees emerging from their soil cavities, just below the leaves of cucurbits. It is also helpful to maintain untilled, marginal areas in close proximity to your squash patch. Learn more about farm management for this and other species of native bees from the Xerces Society.