- Author: Christine Casey
As mentioned in my post of May 1, my position at the Haven is being eliminated. Recognizing that the need for bee gardening information will remain, this post is a summary of resource materials, web sites, and nurseries that you may find helpful in the future. This information is not comprehensive, and some of the recommendations --such as the plant lists-- are California-centered.
Bee books
California Bees and Blooms. Heyday Books. ISBN 978-1-59714-294-6
Insects and Gardens. Timber Press. ISBN 0-88192-504-7. Winner of an American Horticultural Society Book Award, 2002.
Bees, Wasps, and Ants: The Indispensable Role of Hymenopters in Gardens. Timber Press. ISBN 978-0-88192-988-1.
The Bees in Your Backyard. Princeton University Press. ISBN 978-0-691-16077-1. Available in a Kindle edition and in a spiral-bound edition. Both are great for taking into the garden.
Gardening books
California Native Plants for the Garden. Cachuma Press. ISBN 0-9628505-8-6
Sunset Western Garden Book. Time Life. ISBN 0-376-03920-5
The California Native Landscape. Timber Press. ISBN 978-1-60469-232-7
Web sites
UC Davis Bee Haven: http://beegarden.ucdavis.edu
UC Berkeley Urban Bee Lab: http://www.helpabee.org/
UC Cooperative Extension San Diego: https://ucanr.edu/sites/PollinatorAttractiveness/
Where to buy bee plants. This is not a complete list or a recommendation.
Davis, Dixon, and Woodland
Lemuria Nursery: https://www.facebook.com/LemuriaNursery
Redwood Barn Nursery: http://redwoodbarn.com/
UC Davis Arboretum plant sales: http://arboretum.ucdavis.edu
Sacramento area
Green Acres Nursery & Supply: http://idiggreenacres.com
The Plant Foundry: https://www.plantfoundry.com
California Native Plant Society plant sales: http://cnps.org/
San Francisco Bay area
Annie's Annuals: https://www.anniesannuals.com/
Berkeley Horticultural Nursery: http://www.berkeleyhort.com/
California Flora Nursery. http://www.calfloranursery.com/
Cottage Gardens of Petaluma: http://www.cottagegardensofpet.com/
Mostly Natives Nursery. http://www.mostlynatives.com/
Watershed Nursery: https://www.watershednursery.com/
California Native Plant Society plant sales. http://cnps.org/
Chico and Redding area
Floral Native Nursery: http://floralnativenursery.com/
Little Red Hen Nursery: https://www.littleredhen.org/pages/plant-nursery
McConnell Arboretum plant sales: https://www.turtlebaynursery.org/
The Plant Barn: http://theplantbarn.com/
California Native Plant Society plant sales: http://cnps.org/
Southern California
Tree of Life Nursery: https://californianativeplants.com/
Las Pilitas Native Plant Nursery: https://www.laspilitas.com/
Theodore Payne Foundation Retail Nursery: https://theodorepayne.org/plants-and-seeds/nursery/
California Native Plant Society plant sales: http://cnps.org/
Soils and water
UC Davis SoilWeb: http://casoilresource.lawr.ucdavis.edu/gmap/
Water Use Classification of Landscape Species (WUCOLS): http://ucanr.edu/sites/WUCOLS/
- Author: Christine Casey
A previous blog covered the steps to take before starting a bee garden. Now it's time to talk about the plants and how to take care of them.
Plant selection depends on many factors, including personal preference, climate, soil type, irrigation frequency, and plant availability. There are numerous bee plant lists available, some of questionable reliability (1). I recommend using a plant list from a reputable source like a university or cooperative extension website. Use national lists based on USDA planting zones carefully. USDA zones are based on average low temperature and place areas with vastly different rainfall and humidity in the same zone. For example, southern Florida and central California are in the same USDA zone; clearly Florida plants won't grow in dry California and visa-versa.
In California, a good starting point is the Haven's list of low-water bee plants shown below.
Once plants have been selected, it's time to place them for planting. Some gardeners like to plant from a plan like this one, while other prefer to 'wing it'. Plant numbers in this diagram refer to numbers on a planting list. I like to come up with a base plan and then alter it by moving plants around to their final position.
Dig a hole that's slightly wider than the root ball. If you're planting at time when it hasn't rained for at least a week, I suggest filling the hole with water and letting it drain before placing the plant. Refill the hole with the native soil after planting. Tamp down the soil, water, and mulch. The low-water plants widely used in California gardens should be planted slightly higher than the ground level to ensure good drainage. Water needs in a new garden will vary with the plants, site, soil, and weather. A general rule is to water daily the first 7 to 10 days, every other day for the next 7 to 10 days, and then weekly the rest of the summer.
It's also important to leave some bare soil for ground nesting bees. It doesn't have to be a large area; leaving a mulch-free area along a foundation, as shown here, is fine.
High insect diversity in the wild is seen at the edges where two different habitats meet, such as a forest and a meadow. Recreate this in your garden by placing your bee garden to run along the front of a shrub border. Grouping plants of the same species together also makes bee foraging more efficient. For more ideas about bee garden design drawn from research, see this previous post.
Bee garden maintenance comes down to one word: pruning. It's essential to deadhead as frequently as possible to ensure constant new flower growth. And in the winter, do hard pruning of semi-woody shrubs like sages: at the Haven we remove about 2/3 of the plant's growth. This stimulates lots of new shoots, which flower more than older wood.
References
1. Garbuzov, M. and F. Ratnieks. 2014. Listmania: The strengths and weaknesses of lists of garden plants to help pollinators. Bioscience 64: 1019-1026.
2. Majewska, A. and S. Altizer. 2018. Planting gardens to support insect pollinators. Conservation Biology 34(1): 15-25. PDF of this paper is here.
- Author: Christine Casey
I've spoken with countless gardeners over the years who wish to start their own bee haven. That's great -- the bees need all the help we can give them. But the most misunderstood part of the process is how much preparation needs to take place before a single plant goes in the ground.
As the Haven winds down, I'd like to share some tips on preparing to install your own bee garden.
Many gardeners are removing a turf lawn to create their bee haven. It's important to take the time to do this correctly so your garden doesn't revert to a weedy mess. UC IPM has great information about turf removal, including how to identify your turf species (knowing your species helps with removal) and how to remove existing turf.
If you are opposed to using herbicides to kill your lawn, solarization can also be used. For most lawns it will take longer and be less effective. That is definitely the case for bermudagrass lawns that are common in California. Figure 1 summarizes the pros and cons of various turf removal methods. For more own bermudagrass lawn, I used a combination of herbicides, sheet mulching, and hand removal.
Finally, weed barrier fabric is never recommended. It prevents ground-nesting bees from accessing the soil, traps weed seeds that grow through the fabric and become impossible to remove, and breaks down over time to leach microplastics into the ground.
Whatever methods you use, patience is key. Plan on at least one year of preparation before planting.
It's also essential to know your soil type and its physical characteristics. Jar tests and drainage tests provide important information about how your soil will hold water. In California, the UC Davis Soil Web has detailed soil maps; these may be less accurate if you are in a new development where there has been recent soil disturbance or addition of new topsoil.
Finally, watch the pattern of sun and shade in your garden for a year before planting. Many winter-blooming 'full sun' plants will do fine under deciduous trees as they are in full sun when flower buds are forming. In the hotter part of California, some 'full sun' plants may need shade in afternoon.
The final task while you're in the process of killing your lawn is to learn about and choose plants for your garden. Garden tours are a great way to start this process....you'll see what grows in your area and have the chance to speak to other gardeners. These are often sponsored by municipal water authorities. Botanic gardens and independent garden centers with knowledgeable staff are other great resources.
The UC Master Gardener program has trained volunteers throughout the state to provide research-based gardening information. They are a fantastic resource and hold educational programs like this one for the public. Finally, garden clubs and the California Native Plant Society hold tours, plant sales, and educational events.
- Author: Christine Casey
I've written previously about the Haven's research on bees and gardens. This work included a look at bee preferences for common California landscape plants and work to help growers and landscapers provide the healthiest plants for bees.
Studies on bee plant preferences were described in this blog post, and the first year's results (2022) of our current project developing bee sampling methods for growers and landscapers was described in this post.
The current project is an evaluation of a common insect sampling method, timed counts, with a novel method called snapshot counts. As the name suggests, the snapshot methods uses several quick counts rather than one longer timed count to assess the number of bees choosing a plant. Our goal was to see if the faster snapshot method could provide bee counts with accuracy similar to the widely used timed count method.
The speed of the snapshot method could allow it to be included with other routine insect sampling done by growers and landscapers. This would provide a way to assess the relative attractiveness of a nursery or landscape plant mix to bees, allowing for both accurate plant recommendations and targeting of bee-compatible pest management.
Trials took place at locations in San Diego County, the center of California's nursery industry.
While the average number of bees observed per plant differs between the two methods, the pattern of preference is the same for both (Fig. 2). This is confirmed by regression analysis (Fig. 3), which found a strong correlation between the two methods
Our goal was not to determine the absolute number of bees expected on a plant, as that will vary with location, season, and weather. Rather, we wanted to understand which plants are more likely to be chosen within a plant mix. Growers can then compare new plant varieties to those with known attractiveness to determine how they'll fit into a bee garden.
- Author: Christine Casey
- Author: Lea Corkidi
Regular Haven visitors notice that we frequently change our planting. It's one of the joys of gardening -- there are always new plants to try and experiment with. At the Haven, research on new plants and methods for bee gardens is essential to our educational mission.
Previous posts have reported on our work with bee plant preferences, with an emphasis on low-water plants. Our colleagues at UC Cooperative Extension in Southern California have done similar work for that part of the state. Previous blog posts have covered research with mulch, plant color, and water; all are important components of a healthy bee garden.
But all this is for naught if it isn't put into practice. So our current work is to create tools for the California horticulture industry to educate employees and customers about bee garden best practices based on this research. The first step in this work is development of an efficient sampling method so growers, landscapers, and public gardens can easily assess the bee-attractiveness of new plants as they come on the market. This will allow these plants to be marketed correctly, and will also help growers to target bee-friendly pest management.
In our attractiveness studies the Southern CA team used timed counts, while the Northern CA team used a snapshot count method (1). This technique consists of 20 second quick counts of every plant that is repeated three times in succession rather than a single 3-minute timed count. The snapshot count is faster to complete and more readily worked into the day of an otherwise busy nursery employee.
The purpose of this study was to calculate the relative net precision (RNP) of each bee counting method at a wholesale nursery (Fallbrook, CA) and a public garden site (Encinitas, CA) in San Diego County. RNP is calculated as shown below and is a way to assess sampling efficiency by balancing precision and sampling cost (2).
RNP = [1/(cost x Rv)] x 100, where Rv = (SE/mean) x 100
Plants in full bloom were sampled weekly for at least 4 weeks using both methods. Bees were counted as honey bees or other bees as this distinction is easy for an untrained observer; only honey bee data is reported here. At both locations, we saw a larger absolute number of bees with the snapshot method, but the trend of most attractive to least attractive was the same for both methods (Figures 1 and 2). We are most interested in this trend rather than the absolute number, which is expected to vary between locations. Additionally, regression analysis shows that the two counting methods are strongly correlated (Figure 3).
Finally, we saw differences between the RNP values calculated for the two sampling methods, with higher RNP for the snapshot method at both locations (Table 1). Higher RNP means greater sampling efficiency (2).
A second year of study will begin in April at additional sites to confirm these findings. We look forward to providing the California green industry with a useful tool for supporting pollinator gardens.
References
1. Garbuzov and Ratnieks. 2014. Functional Ecology 28: 364-374.
2. Buntin pp 99-115 in Handbook of Sampling Methods for Arthropods in Agriculture. CRC Press, Boca Raton, FL. 1994.