Friday, May 15, 2009

Build a Bee Condo

Norfolk city ordinance prohibits keeping bee hives inside city limits on less than 5 acres of land, yet we all know that bees are important pollinators of our favorite fruits and vegetables as well as some flowering plants. And, of course, we all heard the news reports that the most common hive bee, several varieties of European honey bees, are in deep trouble because of a little understood condition called Colony Collapse Disorder. So how does a Norfolk gardener get his plants pollinated?

The answer is native bees, of course. So while most of us don't have enough property to keep bee hives in Norfolk, we can encourage native bee habitat in our gardens, just like we do for birds and butterflies. (For you tomato growers, you should know that the common honey bee is virtually useless at pollinating tomatoes anyway. We know from experience and university studies that tomatoes varieties that are not self pollinating are pollinated best by native bees or other insects, not honey bees.)

Many varieties of native bees live in our area--bumble bees, sweat bees, digger bees, long-horned bees, carpenter bees, leaf-cutter bees, and mason bees are probably the most common--and each requires its own habitat. University studies show that the champion native bee pollinators is the long-horned bee, but all are highly useful. Most native bees are solitary or small community nesters and none are aggressive. In fact, native bees are quite docile--male bees don't have stingers--and most native females have to be severely threatened to be provoked into stinging you.

I mentioned that honey bees are not good tomato pollinators. This is not the fault of the honey bees but the tomato plant, which doesn't give up its pollen easily to just any bee. As I mentioned, most varieties of tomatoes are self pollinating, but certain popular varieties--like cherry tomatoes--require insect pollination and even self pollinators could use the help of a good bee. Bumble bees, in particular, have mastered the art of "buzz" or sonic pollination of tomato plants.

To buzz pollinate, a foraging bumbler will grab hold of the tomato flower with all six legs and flap her wings furiously, transmitting all her energy into shaking the flower. When you hear this going on in your garden, it sounds like the bee is angry. But that's just the sound of bumble bee working hard to help you get more tomatoes. This violent sonic vibration causes the tomato flower to spew out pollen, which covers the bee and floats to other tomato flowers. You can do this yourself using a tuning fork--about Middle 'C' works well--but a lazy gardener would just let the bees do it.

So how do you encourage native bee habitat? By providing the essentials--water, food, and shelter--and stopping or limiting your use of pesticides, particularly insecticidal dusts, which stick to the bees and then are ingested when the bees clean themselves. Garden plantings for native bees is for another article, but if you are butterfly gardening or fruit or vegetable gardening, then you're well on your way to having the right food habitat for bees, which need nectar for energy and pollen for protein (you didn't think they were doing all this work for free, did you?).

What native bees need most from you is a little home in a quiet corner. There are two good ways to create habitat for native bees. The easiest native bee home to build is a bundle of reeds or hollow stems of various diameter, such as bamboo, cut in 6-8 inch lengths. Be sure to cut bamboo at the node so that there is an open end and a closed end. Then bundle 15-20 tubes with closed ends grouped together. I wedge my bundle of bamboo at the 'Y' where the rain gutter down spout bends inward to meet the house. A rafter in a carport, open garage or the crotch of a tree would work just as well, too, someplace where the nest will stay relatively dry and out of the weather.

The second way to build a native bee habitat is to drill nesting holes into a block of UNTREATED wood. A scrap 6-inch long piece of 4X4 (drill into the cut end to get the proper depth) or a length of 4X4 screwed to a 2X6 mounting board works fine. Holes should be 3/32 to 3/8-inches in diameter on 3/4-inch centers. Holes larger than 1/4-inch should be 5 to 6-inches deep. Smaller diameter holes should be 3 to 4-inches deep. Do not drill through the board! The hole must be closed at one end and fairly smooth inside. Then mount your bee condo on a fence post, tree, or outbuilding 3 to 6-feet off of the ground. A slight downward slope will keep most rain out.

Here's a picture of a luxury native bee condo that combines both of these ideas and then adds a roof.

Bumble bees are ground dwellers, so a clear and undisturbed patch of garden is all they need. Often bumblers will set up a small brood in an abandoned mouse hole. Many beekeepers make nesting boxes for bumble bees--a small wooden box buried with all but a length of 3/4 inch PVC pipe exposed for an entrance --and later rent their bumble bees to commercial greenhouse operators who need reliable pollinators.

For more information, see the Xerces Society web site or pick up the may-June 2008 edition of Audubon magazine.

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