Before a flower can set seed or form fruit, it needs to be pollinated. Though some plants are pollinated by bats, birds, butterflies, moths, and wasps, most of the work is done by bees.
Bees are in serious trouble, though. Their numbers are in sharp decline, mainly because of shrinking habitat. Fortunately, bees have some dedicated advocates like the Xerces Society. And home gardeners can help too. Here's what you can do to promote a bee-friendly environment in your garden.
Grow plants that bear flowers with plenty of nectar and pollen. Some native bees and native plants, including penstemon and salvia, are literally made for each other.
Old-fashioned, heirloom-type flowers like bee balm, black-eyed Susan, cleome, sunflower, and zinnia are also excellent; they have more pollen and nectar than highly developed hybrids.
Lavender, rosemary, thyme, and many other herbs also have blossoms that bees favor.
It's also helpful to include a large range of colors in your garden, especially blue, violet, white, and yellow.
Aim to have something in bloom from early spring to late fall so that winged visitors are never without nourishment.
One of the biggest challenges bees face is finding suitable nesting sites. We're not suggesting you house honeybee colonies; that's for professionals.
But the majority of our approximately 4,000 species of native bees (honeybees are a European import) are solitary ― essentially, single mothers raising their young alone. Having no hive to defend, they're not aggressive and rarely sting.
About 70 percent of native bees are ground nesters. A small patch of bare earth in a sunny spot ― as little as 1 square foot ― is all they need. When mulching your garden, be sure to leave some bare areas.
The remainder are mostly wood nesters: They'll occupy holes in trees bored by beetles, or they'll move into nesting blocks like the one shown opposite. The female bees will lay their eggs in the holes, then seal them; their offspring will emerge next spring to carry on.
Next: how to make a nesting block
Make a nesting block
Many bees make themselves at home in holes drilled in wood blocks.
To make a nesting block, you'll need a piece of wood at least 4 inches deep and 8 inches long. Use untreated lumber and avoid cedar, which is toxic to insects.
Drill a grid of holes varying from 3/32 to 3/8 inch in diameter, spacing them approximately ¾ inch from each other. Drill deep holes, even going all the way through the block, to maximize the nesting depth.
Attach the block to a backing board and install a sloping roof that extends in front of the block to shelter the holes from the elements. Mount the backing board on a sturdy fence, post, tree, or building in a site where the holes will get only gentle morning sun.
You can buy a ready-made nesting block for orchard mason bees from Planet Natural ($18; 800/289-6656). Or try the Countryside Culture Mason Bee Block House, Northwest Nature Shop; 877/482-3241.
Encourage native bees ― and gather information about them ― this summer by participating in the Great Sunflower Project. Get free seeds, and help map pollination all over the country. Go to Great sunflower.org for details.
Among the many problems with chemical controls is that they are nonselective: They don't just kill pest insects, they kill bees too.
Instead of using pesticides, provide a rich array of native plants to attract beneficial insects like lacewings and lady beetles, which devour aphids, mealybugs, and whiteflies.
The Xerces Society (503/232-6639), a nonprofit organization working to protect bees and other invertebrates, is a great source of additional information, especially its Pollinator Conservation Handbook (2003; $23, including shipping), written in association with the Bee Works and illustrated with revealing close-up photos of bees, butterflies, and other pollinator insects.