Cultivating pollinators aids harvests

Posted March 05, 2010, at 5:06 p.m.

One out of every three bites of food you eat depends on insect pollination. In the garden, you depend on pollinators, mainly bees, for success with tomatoes, peppers, eggplants, summer and winter squash, cucumbers and melons, peas and beans, strawberries, blueberries and other small fruits.

As you plan for the coming season in the garden, what steps will you take to ensure that these all-important pollinators will be there with you?

Honeybee populations have been in decline for more than two decades due to a variety of disorders, leaving it to native bee populations to pick up the slack. I can count on one hand the number of honeybees that I see in our garden each season, but bumblebees and other native bees abound thanks to our efforts to provide them with food and shelter.

We leave part of the garden wild. About a hundred feet from the vegetable garden, we leave a patch of grass and wildflowers for the insects. We never mow this patch and, as a result, there is a season-long supply of nectar and pollen for the bees, including violets and dandelions in spring, goldenrod and Queen Anne’s lace (wild carrot) in summer, asters in autumn. In addition to the pollinators, hoverflies and other beneficial insects thrive in this spot, completing their life cycles undisturbed while frequently visiting the vegetable garden.

We plant for the bees. A large patch of catmint (Nepeta) in the perennial bed provides bumblebees with a nectar source that lasts for weeks and doubles as a bumblebee playground. I think of it as play to watch the flowerscapes swaying under the weight of bees.

Unlike the honeybee, the bumblebee does not think twice about leaving one nectar source for another. I have watched the same bumblebee move from catmint to allium to summer squash, all in the course of a few minutes. Honeybees tend to forage monocultures, large fields of a single species, and thus are not the best small-garden pollinators.

We weed selectively. What a gardener might consider weed, a native bee considers food, either nectar or pollen. Volunteer calendulas and other flowering weeds are left to flower at the feet of pea plants and in the sunny spaces between squash leaves, attracting a variety of native solitary bees to pollinate the garden plants.

We provide housing for native bees, nest boxes for the solitary bees and opportunities for the bumblebees. An example of the latter is an old stump left slowly rotting at the edge of the catmint patch mentioned above. The bumblebees took to this stump, building an underground nest beneath it. I sit near the stump and watch the bees disappear down a hole in the ground.

Bumblebees are finicky about their nest sites and do not always appreciate the gardener’s efforts to help, although I still want to try burying an old teapot, leaving the spout at ground level as an entrance hole. It is better to leave natural nesting sites, like the old stump, or an abandoned mouse hole, for them to use. In other words, don’t be too tidy around the garden — what looks like a pile of sticks to you might cover the entrance to a bumblebee nest.

We do not use any pesticides. Period.

Every tomato you harvest from your garden this coming year will likely have been pollinated by a bumblebee. Yes, tomatoes are self-pollinating, but only after the bee shakes the pollen from the anther by a unique technique called “buzz pollination.” The bumblebee grasps the flower and moves its flight muscles rapidly, causing the anther to vibrate and release the pollen.

Bumblebees know how to enjoy life.

Send queries to Gardening Questions, P.O. Box 418, Ellsworth 04605, or to rmanley@shead.org. Include name, address and telephone number.

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