Some crops, like squash, are dependent on bees for pollination and fruit production.
We sometimes hear from customers whose first squash of the season shrivel. Cool, wet weather and fewer honeybees may be the cause. The weather usually corrects itself as summer arrives, and there are ways to encourage some special native bees—the sweat bee, the bumblebee, and the squash bee—in your garden. These indigenous bees can pollinate both earlier and later in the year than honeybees.
Big Bumblebees Work Early, Stay Late
Bumble bees do indeed bumble about the garden, rocking flowers as they park their big bodies for a moment. Credit: Gary Alpert, Harvard University, Bugwood.org
Almost everybody knows big, furry, black-and-yellow bumblebees. They get busy early in the season, earlier than honeybees, so they’re a big help for early squash. Bumblebees live in little cavities in soft ground, or they move into holes already present, like old mouse nests. They will visit many crops, including watermelon, cucumber, cantaloupe, beans, okra, and herbs such as lavender and bee balm. Bumblebees live in colonies started by a queen each spring that can number in the hundreds.
Tiny Sweat Bees Visit Many Crops
Sweat bees are pretty little bees that often have a metallic coloring. Credit: Susan Ellis, Bugwood.org
Sweat bees are smaller, often metallic green, black, blue, or yellow bees that like to rest near the center of flowers in your garden. They are called sweat bees because they sometimes forage for the salt in human sweat. Just ask a farmer. Sweat bees have very small stingers and sting only if bothered. They’re active from late spring until fall, and busiest from sunrise until about 11:00 a.m.
Sweat bees dig a small tunnel in compacted, undisturbed earth to nest; they live alone and don’t have a queen. Because they are small, individual bees can’t carry much pollen, but there is strength in numbers. They are abundant in most gardens and will visit an array of Bonnie flowers and herbs such as petunias, sweet basil, bee balm, lavender, and mint. They will also pollinate cantaloupe, pumpkins, tomatoes, peas, eggplant, and strawberries.
Squash Bees Are Uniquely Suited for Squash
Squash bees, which live east of the Rocky Mountains, are designed to pollinate squash plants and their relatives. The bees have hair on just the right place on their bellies to capture the pollen of one squash flower and place it exactly on the pistil of another. Flying about the garden from June to September, squash bees are easy to mistake for honeybees, but squash bees don’t have a queen and they don’t make honey. For the squash family, better pollination means larger, well-formed fruit, so squash bees are welcomed by cantaloupe, pumpkins, all types of squash, cucumbers, watermelons, and zucchini. Like sweat bees, squash bees are solitary and live only a year. Also like sweat bees, they excavate holes in compacted, undisturbed earth to make homes.
How to Invite Native Bees
Encourage nesting. Perhaps you can lure colonies to your yard with attractive nesting sites, especially in the early spring. Bumblebees like piles of soft soil or compost. Sweat bees and squash bees, on the other hand, prefer compacted earth. Tilling or mowing can disturb and even kill these bees. Try leaving some areas near your plants undisturbed to increase your native bee populations. Bare or sparsely covered ground is the easiest place for these bees to nest, but sweat and squash bees have been known to nest in grassy areas as well.
Plant their favorite foods. Your plants provide nectar and pollen for bees. Have meals for them from early to late in the season. For example, bumblebees can visit blueberries in the early spring and honeysuckle a little later; try planting a patch of bee balm to give bees something to eat throughout the summer. Specialist bees like squash bees do not need extra plants because their life cycle is timed to their target plants, but generalists like sweat bees and bumblebees will benefit from access to flowers from spring until fall.
Be careful about pesticides. The pesticides you may use to control insect pests may also affect bees. Always read the label for warnings about safety for bees. (Incidentally, labels also warn of potential hazards to fish, if you should have a pond.) Pesticides that soak into the ground may reach into the homes of ground-nesting bees and kill them. Bees are most active in the day, so applying pesticides in the evening also helps.
Learn More about Native Bees
There are many other native bees in the US. To learn more about native bees and ways to encourage them, visit http://attra.ncat.org/attra-pub/nativebee.html from the National Sustainable Agriculture Information Service.
