By Susan Lewitt, for Let’s Talk Plants! April 2024.
Will You “Bee” Part of the Solution?
San Diego is a biodiversity hot spot due to our vast number of native plants and native bee species, which makes it the perfect location for designation as a Bee City USA through the Xerces Society’s program of the same name. This will mean a need to increase methods to support these native bee species such as native rooftop gardens and native community gardens, efforts that will help sustain our ecotourism and agriculture.
“Bee City USA is not just a designation, it’s a commitment to biodiversity, pollinators and reducing harmful pesticide use,” said City Councilman Joe LaCava of La Jolla, who spearheaded efforts that culminated with council approval August 2023.” (“San Diego is now a Bee City USA in an effort to protect the crucial pollinators” by David Garrick Aug. 17, 2023, 10:30 AM PT. La Jolla Light.)
Deer Weed, Acmispon glaber, appeals to Bumble Bees. Left photo courtesy of Calscape. Right photo by Bonnie Nickel.
In order to support the more than seven hundred native bee species, their needs must be met for food sources, shelter and nesting areas. Some of you may be squirming at this point because you are probably thinking that more bees mean more chances to get stung. That may be somewhat true with Honeybees, and Yellow Jackets, a wasp species, but our native bees are nonaggressive. Many are solitary, making it too risky to sting someone. Also, quite a few of our bees are very tiny.
Santa Barbara Milk Vetch, Astragalus trichopodus var. lonchus, is favored by Bumble Bees because of its tubular flowers. The Rhus Fairy Bee (Perdita rhois) likes the tiny white clustered flowers of Toyon, Heteromeles arbutifolia, right. Left and right photo by Keir Morse. Middle photo by Bonnie Nickel.
What do our seven hundred plus native bee species need?
There are several things you may try in your own garden. Many of them are ground nesting and therefore need a sunny patch of bare soil free of mulch, plants and weeds. Weed barriers, whether they are mesh or black plastic, tend to be a deterrent, making it hard for our bees to get to the ground where they can dig out a nest. A good alternative weed barrier is newspapers, which degrades over time.
You may see some Chimney Bees (Diadasia sp.) visiting native plants like Island Morning Glory, Calystegia macrostegia. Left photo by Keir Morse. Right photo by Bonnie Nickel.
Carpenter Bees utilize soft wood, like pine, Pinus spp., or fir, Abies spp., and will thank you by pollinating your produce garden. They also like to nest in Agave, Agave spp., Cottonwood, Populus fremontii ssp. Fremontii, and Yucca, Yucca spp. Leafcutter Bees use Redbud, Cercis occidentalis, and plants from the rose family, Rosaceae, to line their nest with leaf cuttings from these plants. Wool-carder Bees gather fuzz from plants such as Wright’s Cudweed, Pseudognaphalium canescensto, to line their nests. Leaflitter should be left under shrubs for Digger Bees who prefer to be hidden. Mason Bees dig into logs to create their nests, and also use existing holes in wood that they enhance with mud; to supply them with mud, keep a bare patch of soil moist or provide a shallow dish of mud. Cellophane Bees, also known as Polyester Bees, make a waterproof lining for their nests using material from native plants.
Native bees are seen here on Ceanothus (middle) and Goldenbush, Isocoma menziesii, (right). Right photo by Keir Morse. Middle photo by Bonnie Nickel.
Mason Bees and Leafcutter Bees will make use of artificial nests.
“Fill a coffee can with a bundle of drinking straws, mount it to a fence post in a protected area, and you’ve got yourself an artificial nest for these efficient pollinators. If you’re handy, drill some holes in a block of pine or fir wood instead.” (12 Things You Can Do to Help Native Bees, Roll Out the Green Carpet for Native Pollinators, https://www.thoughtco.com/how-to-help-native-bees-1968108)
Some Mining Bees (Genus Andrena) are attracted to Lemonade Berry, Rhus integrifolia. Fruit of the Lemonade Berry shown on the right. Left photo by Bonnie Nickel. Right photo by Keir Morse.
Bees also prefer lawns that are not mowed. Lawn mowing is potentially deadly to bees, so if you must mow, do it during times of the day when bees are less active, such as early morning, or late afternoon, or on cloudy days. Pesticide use can also be very harmful to our bees and must be used sparingly, or not at all. Natural predators of unwanted insects, such as birds and solitary wasps, can be an ecofriendly alternative to poisons.
Bush Sunflower, Encelia californica, is shown with Metallic Sweat Bees (subgenus Dialictus, left) and Ligated Furrow Bee (Halictus ligatus, right). Photos by Bonnie Nickel.
Finally, our native flowering plants are necessary to attract and provide food for these wonderful native pollinators. Quite a few of our native bees are generalists (polylectic), which means many different species of native flowering plants will support them. This includes some Mining Bees, Woolcarder Bees, Furrow Bees, and Cellophane Bees. Sweat Bees, which are very tiny, and sometimes bright green, are generalists and like to visit quite a few different native plants including Bladderpod, Peritoma arborea, Sea Dahlia, Leptosyne maritima, Ceanothus, Ceanothus spp., Seaside Daisy, Erigeron glaucus, Buckwheat, Eriogonum spp., Cliff Spurge, Euphorbia misera, and California Bush Sunflower, Encelia californica. Carpenter Bees are also generalists, with a preference for large open flowers, but they will also steal nectar by cutting a hole in the base of the more tubular flowers to get to the food source inside. It is important to also include native plants for the specialist bees (oligolectic).
Leafcutter Bees are drawn to members of the pea family which includes Western Redbud, Cercis occidentalis, left. California Aster, Corethrogyne filaginifolia, is hosting this native Metallic Sweat Bee (right). Left photo courtesy of Calscape. Right photo by Bonnie Nickel.
To maximize support of our native bees, be sure to plant a variety of native species that bloom at various times during the year to provide year-round food sources, especially from the beginning of spring through the last days of fall. A native plant that blooms all year long is the Tree Mallow, also known as Malva Rosa, Malva assurgentiflora.
A member of the Sweat Bee family is exploring this native Seaside Daisy, Erigeron glaucus, left. A Texas-striped Sweat Bee, Agapostemon texanus, visits California Buckwheat, Eriogonum fasciculatum (right). Photos by Bonnie Nickel.
Bumble Bees like tubular flowers such as Deer Weed, Acmispon glaber, Penstemon spp., Santa Barbara Milkvetch, Astragalus spp., and Salvia spp. Some Mining Bees are specialists with each species having its own preferred food source such as flowers in the Asteraceae family, or Fabaceae family. One species of bees related to Mining Bees prefers flowers of the Creosote Bush, Larrea tridentata. Another Mining Bee relative specializes in visiting Sand Blazing Stars, Mentzelia involucrate, which can be found in our own Anza-Borrego Desert.
Mason Bees enjoy visiting Oregon Grape, Berberis aquifolium, and help produce edible berries that resemble grapes. Photos by Keir Morse.
Do you like blueberries? You can thank one Mason Bee species, (Osmia ribifloris) utilized by commercial blueberry growers to pollinate their blueberry crops. Another native bee species in San Diego County, a very tiny bee, the Rhus Fairy Bee (Perdita rhois) likes the tiny white clustered flowers of Toyon, Heteromeles arbutifolia, and Laurel Sumac, Malosma laurina. Chimney Bees species (Diadasia spp.) are specialists on cactus with large cup-shaped flowers, and some forage on mallows, while others prefer morning glories.
On the left are leaves of the Munz’s Sage, Salvia munsii and on the right, a Digger Bee is investigating its flowers. Left photo by Keir Morse. Right photo courtesy of Calscape.
Look for some of these native bees, as well as the native plants that they enjoy while you stroll through the 2024 native garden tour on April 6 and 7. https://cnps-sd.squarespace.com/native-garden-tour-2024
In addition to the tour, please visit Calscape (https://www.calscape.org/) for information on which native plants work for your landscaping.
These Laurel Sumac flowers, Malosma laurina, could be waiting in your garden to greet some Rhus Fairy Bees (Perdita rhois). Photo courtesy of Calscape.
Susan Lewitt is a member of the California Native Plant Society (CNPS), participating in their Native Gardening Committee, and their Conservation Committee.