Create an Oasis for Bees & Butterflies in your California Garden

By Susan Kegley, Pesticide Research Institute and Bees N Blooms Farm

Spring is here and there is a buzz and a flutter in the air! With a little planning, your garden can be a haven for bees, butterflies and other pollinators. And they DO need your help!

Over the last 10 years, managed honey bee populations have dropped steeply, with beekeepers reporting heavy losses every year since then. Native bees such as bumble bees are not monitored as closely as honey bees, but those that are being tracked are declining in abundance as well, with the western Rusty Patched bumble bee listed as an endangered species last year. Butterflies are not doing much better—populations of the iconic Monarch butterfly on the west coast are down by nearly 80% since the early 1990s.

There are several factors thought to be contributing to the declining populations of bees, butterflies and other pollinators, with a new class of insecticides—the neonicotinoids—and certain fungicides playing a central role. Other stressors include pests of bees like the Varroa mite and the diseases it transmits, as well as expanding monocultures in agricultural areas that limit the diversity of food sources and habitat for pollinators.

Gardeners and farmers can help bees and other pollinators by providing a pollinator-friendly space with a diversity of pesticide-free plants that provide nectar and pollen throughout the year, with a special emphasis on bee-attractive plants that bloom in late summer and fall. In Sonoma County, spring brings a riot of blooming plants, from apples in Sebastopol to mustard in the vineyards, along with rosemary, ceanothus, and acacia. But when the hot, dry summer arrives, there are very few flowering plants, making it difficult for bees and butterflies to find enough to eat. That’s when your garden or farm should kick into high gear for pollinators.

The best plants for attracting pollinators are those with an abundance of nectar and/or pollen with an open center. Flowers with multiple petals and closed centers like roses and the more exotic dahlias don’t qualify (even though they are beautiful!), since pollinators cannot access the center of the flower. Some plants produce more nectar and pollen than others, including all types of Salvia, poppies, milkweed, borage, native California buckwheats, asters, scabiosa, lavender, Gaillardia, hyssop, veronica, clover, phacelia and sunflowers. Butterflies especially seem to like verbena, milkweed, daisies, coneflowers, cosmos, yarrow, and zinnias. For late summer and early fall forage, plant goldenrod in the spring and sow a final round of sunflowers, phacelia, and annual buckwheat in mid to late July.

Trees and shrubs are another great source of late summer food for bees and other pollinators, providing a three-dimensional field of flowers. Some recommended species include Chaste tree (Vitex), Bottlebrush, Red-flowering gum, and Crape Myrtle, particularly the white variety. If you plant these types of trees, you will know you are helping the pollinators because your yard will be audibly buzzing when they are in bloom!

Native bees such as the familiar black and yellow bumble bees, black carpenter bees, bright green sweat bees, iridescent blue mason bees, and the long-horned bee are common in Sonoma County. Except for the bumble bee, which creates a colony underground, these native bees are solitary, nesting in hollow stems or in the ground. Leaving areas in your yard or garden undisturbed will maximize nesting spaces for native bees, as will leaving your garden a bit messy through the winter. Some natives nest in the hollow stems of last year’s flowers. If you do have to trim your plants in the fall, place the cut stems gently on the compost pile and don’t disturb until well into spring to give the overwintering bees a chance to start the new year. Planting at least part of your garden in blooming California natives ensures a match between the native bees’ nutritional needs and available food.

To ensure your garden or farm is truly bee-friendly, avoid use of bee-toxic pesticides, especially neonicotinoids, which persist in plants and soil for months to years, making the pollen and nectar toxic to bees for a long time. Even low doses of these insecticides have been found to compromise the bees’ immune system, making them more vulnerable to diseases carried by the Varroa mite. Neonicotinoids and some fungicides also impair bees’ ability to reproduce, and even affect the bees’ ability to navigate their way back to the colony after foraging.

Having a pesticide-free garden also requires starting with neonicotinoid-free plants, but finding them can be a challenge. A recent study by Friends of the Earth and Pesticide Research Institute showed that in 2014, 51% of bee-attractive plants sampled from big box stores like Home Depot and Lowes contained neonicotinoids. With the results of the study in hand, Friends of the Earth and consumers asked the big box stores to eliminate these insecticides from their plants, or at least label the plants so gardeners could make informed choices. Many nurseries responded to pressure from retail stores and consumers, and by 2016, only 23% of plants tested from big-box stores contained neonicotinoids, and the treated plants were labeled as having been treated. It’s an improvement, but there is still progress to be made.

Buying local is the best way to ensure that plants you buy are safe for pollinators. Many of the local nurseries in Sonoma County do not use neonicotinoids and can provide a clean source of plants for your garden or farm. Ask the staff to be sure.

Happy gardening!

Useful Resources for Gardeners:

Attracting Native Pollinators, Xerces Society

Farming for Bees, Xerces Society

Bee-Friendly Gardening Resources, Pesticide Research Institute

Best Bee Plants for California, UC Berkeley Urban Bee Lab

Pest Smart Web allows you to find out which pesticide products are toxic to bees (also available as a free iOS app), Pesticide Research Institute

Neonicotinoid Insecticides in Garden Plants, Friends of the Earth and Pesticide Research Institute

Susan E. Kegley, Ph.D.
Principal and CEO
Pesticide Research Institute, Inc.
3883 Petaluma Hill Road
Santa Rosa, CA 95404

© 2018 – All Rights Reserved

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