January 19, 2019
When I heard bees were in trouble, I wondered if there was anything I could do to help them. Turns out there are a lot of things we can do in our gardens to make life better for the bees. Gordon Frankie, at the University of California at Berkeley, has created an experimental bee garden that serves as a research facility and outreach tool for advising gardeners on planting gardens that will encourage bees and other flower visitors.
It’s not just what you plant, but how you plant.
When pollinators spend their day foraging for pollen and nectar, they sometimes play favorites, a behavior known as flower constancy. This is particularly true for honey bees and bumblebees. Flower constancy is displayed when the bees choose some flower species over others, even when alternative choices exist in the same area. In some cases, the alternatives may provide even more nectar or pollen, but they are bypassed as the bees remain faithful to their plant of choice. If the bees visited many different species in the same trip, they might transfer pollen from one species to a different species and pollination wouldn’t occur. That’s why plants are best pollinated when bees display flower constancy, transferring pollen from one species to another flower of the same species.
At UC Berkeley, researchers have found that large patches of one single flower is the most attractive to bees as well as butterflies. If you have the space, each plant species should be planted in a patch of 3 feet by 3 feet or larger. Patches this size provide more nectar and pollen rewards, and allow bees to forage in one spot without having to spend a lot of energy flying from one plant to the next. Bees prefer to practice flower constancy with the least amount of effort.
Bee year blooms
In our climate, it is possible to have something blooming in the garden year-round. With a combination of native and non-native flowering plants, aim for the most blooms during the “bee year,” which is March through October.
Choose carefully. Just because it has flowers does not mean it is an ideal bee plant. Roses are a good example of plants that are not ideal for bees. They have been bred to produce many showy petals, which replace anthers (the reproductive parts of the flower) where bees get the pollen. The same is true for any of the other double flower hybrids where anthers have been replaced by petals. To avoid them, look for flore pleno next to the scientific name.
While all flowers have pollen, not all flowers have nectar. The California poppy is a profuse example. Make sure you have plenty of nectar producing flowers too. One family of nectar-rich plants is the Lamiaceae, which includes useful herbs such as thyme, rosemary, oregano, basil, savory and mint, as well as salvias and lavender. Diversity is important since native bees are more likely to forage on native plants.
The vast majority of bees in California are native bees. We have 1,600 species, which is why most of the pollination going on in your garden is the work of native bees, not honey bees. Frankie wants us to know that between 60 to 70 percent of these native bees live and nest in the ground, which is why native bees need access to bare ground. This means no hardscaping, plastic weed cloth or mulch. Native bees seek bare ground in order to excavate a tunnel with a series of nest cells in which they will lay their offspring. They also need to make many trips bringing nectar and pollen from flowers to the tunnel mouth for provisioning. Frankie recommends leaving half of your garden with bare dirt.
For information on how to bring more bees into your garden, go to the UC Berkeley Bee Garden website at helpabee.org.