Summer 2006

Table of Contents

Insect pollinators are among the hardest working creatures of the natural world - Kelly McAllister photo

Help pollinators help us all

(excerpted from an article by Matthew Shepherd and Mace Vaughan of The Xerces Society for Invertebrate Conservation, a non-profit organization dedicated to protecting inveterbrates and their habitat through science-based conservation, education and advocacy.)

Insect pollinators are among the hardest working creatures of the natural world.

The transfer of pollen grains from the anther to the stigma of the same or another flower, is necessary for plants to produce seeds and fruit. Up to 80 percent of the world's flowering plants rely on pollinators for this transfer.

Insects pollinate two thirds of the world's crop species, whose fruits and seeds together provide 15 to 30 percent of the foods and beverages that we consume.

Pollinators are keystone species in most terrestrial ecosystems. They are essential to the reproductive cycles of most flowering plants, which are a major part of the diet of many birds and mammals. In some areas, these pollinator-supported plant communities bind the soil, thereby preventing erosion and keeping creeks clean for aquatic life.

Despite its importance, in many places the essential service of pollination is at risk. There is a growing body of evidence that the loss, alteration, and fragmentation of habitats and the extensive use of pesticides have contributed to a decline in pollinator populations and reduced fruit set, a trend that has been recorded on all continents.

Pollinator conservation is an easy and straightforward thing to do. Like all wildlife, pollinators need food and shelter, which you can provide by:

• Growing a diversity of native plants whose blooming times overlap to provide flowers throughout the seasons.
• Maintaining a landscape free of poisonous pesticides.
• Establishing nesting and egg-laying sites, with appropriate nesting materials.
• Constructing sheltered, undisturbed places for hibernation and overwintering.

To help bees, butterflies and other pollinator insects, you should provide a range of plants that will offer a succession of flowers, and thus pollen and nectar, through the whole growing season.

Use local native plants. Research suggests native plants are up to four times more attractive to native bees than exotic (non-native) flowers. Native plants are also usually well adapted to your growing conditions and can thrive with minimum attention.

Use heirloom varieties. For the garden, heirloom varieties of herbs and perennials are good sources of nectar or pollen and thus provide good foraging.

Chose several colors of flowers. Bees have good color vision to help them find flowers and the nectar and pollen they offer. Flower colors that particularly attract bees are blue, purple, violet, white, and yellow.

Plant flowers in clumps. Flowers clustered into clumps of one species will attract more pollinators than will individual plants scattered through the habitat patch. Where space allows, make the clumps four feet or more in diameter.

Include flowers of different shapes. There are nearly one thousand different species of bees in the Pacific Northwest, and they are all different sizes, have different tongue lengths, and will feed on different shaped flowers. Therefore, providing a range of flower shapes means more bees can benefit.

Have a diversity of plants flowering all season. Most bee species are generalists, feeding on a range of plants through their life cycle. By having several plant species flowering at once and a sequence of plants flowering through spring, summer, and fall, you will support a range of bee species that fly at different times of the year. A diversity of native flowering plants that support pollinators, from asters to yarrow, are listed on the Xerces website.

Plants also provide other resources beyond food for many insects at different life stages. For example, a butterfly begins as an egg, hatches into a wriggling, crawling caterpillar that bites and chews on plants, has a period of inactivity as a chrysalis, and then emerges as a flying adult that can only drink fluids. Providing for these means more than just flowers for nectar and pollen.

Provide caterpillar host plants. The caterpillars of each butterfly species have their own limited menu of plants upon which they will dine. Female butterflies lay their eggs on or near these host plants and will only be able to lay eggs if there are the right plants. To start with, grow host plants for the more common butterflies you already see flying through your property and then branch out as you learn more. From clover to willow, host plant species are listed on the Xerces website.

Leave hiding places for butterfly pupae. After several weeks of eating and growing, caterpillars need to transform (pupate) into their adult, winged forms. They do this within the protection of a chrysalis. Before becoming a chrysalis, however, a caterpillar wanders in search of a protected site. Depending upon the species, this safe haven could be a bush, tall grass, or piles of leaves or sticks.

Leave overwintering sites. Depending upon the species, butterflies may overwinter (hibernate) as eggs, larvae, pupae, or even adults. You might find them on plants, under leaf litter, under loose bark, or in piles of logs and other debris. To help these hibernators, a little untidiness goes a long way. Two or three weeks before the severe cold of winter sets in, clean up a minimum of leaves and garden debris and create a pile of logs or leaves.

Offer fruit and sap. Adult butterflies need sugar to fuel their search for mates and egg-laying sites. Nectar provides most of this but some butterflies, such as the mourning cloak, get sugars from rotten fruit or the sap leaking from wounded trees. Plates of rotting fruit (such as peaches, melons, or bananas) will attract many of these beautiful insects.

Create mineral and salt areas. Because plants contain very little minerals or salt, many adult butterflies need to find another source of these nutrients. In the wild, they can get these by tasting exposed clay deposits, animal urine, saliva, or even bird droppings. They also will come to mud puddles that you create. Scrape a small depression in the ground, line the edges with pebbles, and add some water each morning. It is best if these puddles dry out by the end of each day.

Maximize sun, protect from wind. Adult butterflies need to be warm in order to fly. Therefore, nectar flowers and larval host plants should be grown in an open, sunny area protected from the wind by large shrubs, a hedgerow, a fence, or some other windbreak. You could also put out large, flat rocks placed in the sun. These rocks will soak up the sun's heat and give the adult butterflies a place to warm themselves.

Provide bee nest sites. The great majority of bees are solitary nesting species that create nests in beetle-riddled snags or dug in the ground. The bees may remain in the nest for a year or more as they pass through the egg, larva, and pupa stages. Wooden blocks drilled with small holes or patches of bare ground can provide secure nest sites.

Avoid pesticides. Alternative methods for controlling specific pests without using chemicals are available, but even these should be used with caution, keeping in mind the various life stages of butterflies and other insects.

You'll also find great advice and information in these books:

The Xerces Society and the Smithsonian Institution. Butterfly Gardening: Making Summer Magic in Your Backyard. Sierra Club Books, San Francisco, CA.

Buchmann, S. L., and G. P. Nabhan. 1997. The Forgotten Pollinators. Island Press, Washington, D.C.

Shepherd, M., S. L. Buchmann, M. Vaughan, and S. H. Black. 2003. Pollinator Conservation Handbook. Xerces Society, Portland OR.

Vaughan, M., M. Shepherd, C. Kremen, and S. H. Black. 2004. Farming for Bees: Guidelines for Providing Native Bee Habitat on Farms. The Xerces Society, Portland, OR