It's the first week of spring at the Haven and our plants are starting to look their best. For those of you who cannot make it to the garden this week, here's a brief tour of what's going on. For those who can make it, I've included some of the bees to look for.

The garden is currently open, although the cities of Davis and Sacramento are now recommending shelter-in-place. If this expands to other areas or becomes mandatory, the garden will close. Check our web page for the latest information.

Now blooming at the Haven:

Ceanothus, many species. For more detail on this genus, see this previous post. 

Western redbud, Cercis occidentalis. This plant provides bright pink flowers early in the year, while leafcutter bees use its foliage for nest construction throughout the summer. This California native needs full sun and little to no summer water. It grows slowly, so it's worth buying a larger size for your own garden. It may be fed on by the redhumped caterpillar; damage occurs towards the end of the season so control is not needed.

Redbud leaves used in a leaf cutter bee nest

Redhumped caterpillars on redbud

Brandegee's sage, Salvia brandegii. This is a long-blooming California native sage. As you can see from the photo, which shows one plant, it can get quite large. Flowering from late January through May, pair it with the summer blooming native Cleveland sage (Salvia clevelandii) for season-long bloom. It also needs full sun and low summer water.

Bladderpod, Isomeris arborea. This is another long-blooming California native. It is at its peak in the spring, but will produce some flowers year-round. Our single plant is about 6 feet by 6 feet. Needs full sun and little to no summer water. 

Firecracker penstemon, Penstemon eatonii. This bright red California native is used more by hummingbirds than bees, and adds a jolt of color to the early spring garden. It's soon to be followed by the foothill penstemon, a bee favorite. The firecracker penstemon can take part shade and will re-bloom if given some water after the first flush of flowers. Like most of our native penstemons, it will go dormant in the heat of the summer, at which point watering should stop.

Bees to look for this week include honey bees and the blacktailed bumble bee, Bombus melanopygus. The latter seems to like the Brandegee's sage, so look for it there.

Blacktailed bumble bee, Bombus melanopygus, male on Brandegee's sage

We've all seen them....garden catalogs or magazine articles with cute little bee houses hanging like birdfeeders, or entire fences made of nesting tubes for solitary bees. We even had them at the Haven -- for a while -- in the form of bee condos. The only problem? They often don't work, and may even do more harm than good.

While the attention devoted to declining bee populations by the gardening world is great, lots of attention to an issue can often lead to misinformation. This led to greenwashing, with manufacturers rushing to claim often dubious 'green' credentials for their products. We now see the same happening with bees; the term 'beewashing' was coined by Scott MacIvor and Laurence Packer of University of York University to describe this phenomenon as it relates to solitary bee houses. In a study of 600 solitary bee nests that they placed in Toronto, they found that native wasps were more abundant than bees, close to half of all bees using the nests were introduced species, and that parasitism of bees using the nests increased as the size of the nest groups increased.

This is not limited to bee houses; previous investigation by Mihail Garbuzov and Francis Ratnieks of the University of Sussex found similar misinformation surrounding bee plant lists. They reviewed lists published for various regions worldwide, and found large variation in recommended plants, even within the same region. The science behind the lists, such as university research or repeated monitoring by trained observers, was also often unclear.

 

So what's a conscientious bee gardener to do?

Bee houses

I've written extensively about solitary bee houses on this blog. In the wild, bees nest in abandoned beetle galleries in trees. This environment is dark, stationary, and made of wood, and can inform our choice of solitary bee housing. Consider the following:

1. Bees will use a nesting tube diameter that corresponds to their body size. A good range of sizes for common bees is 3/16 to 5/16 inch. Tubes should be 4 to 6 inches deep; anything shorter will produce predominantly male bees.

2. Bees will not use houses or nesting blocks that move or are open in the back

3. A shaded entrance is important; even a piece of burlap draped over the top of the nest can work

4. Bee houses constructed of wood seem to be preferred

5. Position house with entrance out of the prevailing wind

6. Pathogens can build up in bee houses as they are used; they cannot be sterilized with bleach or other disinfectants. 'Cleaning' the used nesting tube with a drill bit or brush is likely to push pathogens into the wood. Houses (in the case of wood blocks) or individual tubes should be replaced after they are used. 

7. Consider all dimensions. Bees may nest in hollow stems that are not horizontal.

 

Sedum 'Autumn Joy' showing hollow stems after fall pruning. These may be used by solitary bees the following spring.

Nesting tubes in use. Note that tubes are filled with different material depending on the bee species. Materials include leaf pieces, leaf hairs, and bits of decomposed granite. Tubes on the upper right with chewed holes have been exited by newly emerged bees.

Leafcutter bee nest cross section. Each segment is an individual egg and food provision. The different shape of the front and back of the segment helps the emerging bee to orient itself to the correct direction for exit.

A fact sheet about building and using solitary bee houses is here.

Bee garden plant selection

Use bee plant lists from reputable sources, such as the Haven or the UC Berkeley Urban Bee Lab. These lists are based on years of observation throughout California by bee scientists. The Haven is participating in a 5-year USDA-funded project evaluating plants for bees; in addition to these field plot studies, bee use of plants in the Haven is monitored weekly by student interns and citizen science volunteers. This ensures that our plant recommendations are based many observations across variations in time and weather.

 

My last post covered the use of color in garden design from the perspective of what bees see. While aesthetics are important in any garden, the needs of bees come first at the Haven and other bee gardens. Here are a few examples of color combinations that are attractive to us and provide both pollen and nectar for bees.

Shades of purple throughout the year

As was mentioned in my last post, purple is a color that bees see well. Here are some ideas for shades of purple throughout the year:

Winter: rosemary (nectar), germander (nectar), ceanothus (pollen and nectar), phacelia (pollen and nectar)

Spring:ceanothus (pollen and nectar)

Summer: sages (nectar), Russian sage (nectar), zinnia (pollen and nectar), cosmos (pollen and nectar)

Fall: aster (pollen and nectar), bluebeard (pollen and nectar)

Tansy-leaved phacelia (Phacelia tanecetifolia)

Aster 'Fanny's' (Symphyotrichum 'Fanny's)

Bluebeard (Caryopteris x clandonensis)

Shades of yellow throughout the year

As a complementary color to purple, yellow is attractive against any of the plants listed above. Some yellow flower choices include:

Winter:bidens (pollen and nectar), blanketflower (pollen and nectar)

Spring:bidens (pollen and nectar), blanketflower (pollen and nectar), lupine (pollen and nectar)

Summer: sage (nectar), sunflower (pollen and nectar)

Fall: sunflower (pollen and nectar)

Yellow lupine (Lupinus microcarpus densiflorus)

Sunflower (Helianthus anuus), unknown cultivar

Summer whites

Spring: Santa Barbara daisy(pollen and nectar), buckbrush (pollen and nectar)

Summer: Santa Barbara daisy (pollen and nectar), gaura (pollen), veronica (pollen), coneflower (pollen and nectar), zinnia (pollen and nectar), cosmos (pollen and nectar), California buckwheat (pollen and nectar)

Fall:gaura (pollen), California buckwheat (pollen and nectar)

Gaura (Gaura lindheimeri)

Coneflower 'Pow Wow White' (Echinacea purpurea 'Pow Wow White')

Zinnia (Zinnia elegans)

California buckwheat (Eriogonum fasciculatum)

Hot colors throughout the year

Winter: California poppy (pollen), Cape balsam (pollen and nectar)

Spring: Cape balsam (pollen and nectar), sage (nectar)

Summer: Cape balsam (pollen and nectar), coneflower (pollen and nectar)

Fall: Cape balsam (pollen and nectar), sage (nectar), sedum (pollen and nectar)

Coneflower 'Magnus' (Echinacea purpurea 'Magnus')

Sage 'Hot Lips' (Saliva microphylla 'Hot Lips')

Cape balsam and sedum 'Autumn Joy' (Hylotelephium spectabile 'Autumn Joy'; bright pink in back of photo)

Spring is here, and planting is underway in bee gardens throughout California. And planting, especially if you're creating a new garden, means you are thinking about design. In this series of posts I will cover various aspects of garden design -- such as color, texture, shape, and size -- from the perspective of what bees need. Based on research, this information should provide a solid foundation for a successful bee garden.

This post will focus on color. An understanding of color theory is helpful in creating an aesthetically pleasing garden for us, but color is also relevant for bees. All color wheel screen shots shown here are from the Adobe web page. 

1. Complementary colors. Colors opposite each other on the color wheel are complementary; this is one of the easiest ways to select colors. Using opposite colors together makes each color appear more vibrant.

Purple and yellow are excellent complementary colors for a bee garden

2. Analogous colors. Colors adjacent to each other on the color wheel are analogous; using these colors can be a bit trickier, especially with hot colors like oranges and reds. One way to combine these effectively is to mix in white, as is done here with white gaura in this planting of the analogous colors pink (echinacea) and purple (tall verbena).

Analogous colors can be softened with white flowers

3. Shades of one color. This is the easiest combination to pull off. Cool colors (blues and purples) tend to create a calming effect and make the garden appear larger, while warm colors (reds and yellows) create energy and make the garden appear smaller. Here is an example of shades of a cool color (purple) used in the Haven: 

Shades of purple in the Honey Bee Haven

So how do we meld this with bee biology? Here are some pointers:

1. Bees see color differently than we do. They don't see red at all, and see purple very well....there's a reason we have so many purple flowers in the Haven. Here's an example: the first photo shows a flannel bush flower in daylight, while the second shows it under ultraviolet (UV) light, which is the light spectrum where bees see. The 'invisible' nectar (to us) is a bright blue beacon to bees under UV light.

Flannel bush flower as bees see it

But, you might be thinking, I see bees on red flowers all the time! Well bees can use more than color to find a flower, which brings us to scent....I'll discuss this in a future post. 

2. Does color pattern in the garden matter to bees? One study (Proc. R. Soc. London B. 2003. 270: 569-575) found that honey bee foraging distance was longer in simple landscapes; this makes sense because honey bees do best with a varied diet and need to travel further to find a mix of flowers in a simple landscape. Conversely, waggle dance activity was greater in complex landscapes because the patches of plants were more variable -- high quality and low quality plants were mixed together. So it's also important to ensure a good mix of high-quality bee plants in appropriately-sized patches.

3. Another aspect of flower color often not considered is patterns on the flowers themselves. Called nectar guides, these serve to guide bees into the nectary. Of course they pick up and deposit pollen as they do this, thereby pollinating the flower.

For lots more detail about how bees see, check out this article. My next post will cover shape, size, scent, and texture. I'll finish with suggested plant lists and planting plans. Here's to your successful bee garden!