As we move into the hottest, driest part of the summer, many of our gardens are looking a bit worn out. It's certainly easier to stay inside where it's cool and put garden tasks off until the fall.
But the bees are still out there doing their work to bring us food and create habitat for wildlife. What are the plant options for California gardens that will stand up to the heat with little water (all these plants are rated ‘low' in WUCOLS) and be loved by bees?
One great choice is our native California aster, Symphyotrichum chilense. Unlike asters native to the eastern US and Europe, which need regular water in California, this one thrives on low water. Shown here are the cultivars, 'Purple Haze' and 'Point St. George'.
'Purple Haze' is about 2 feet tall, while 'Point St. George' grows low to the ground. The former has deeper purple flowers than in typical for this species. Both need full sun to light shade and will spread (a lot!) to cover an area. Consider yourself warned when choosing an area to plant these in.
In our studies of bee plant preference at UC Davis we found our native aster to be one of the most attractive plants to California native bees. The late summer flowers are a critical source of nectar and pollen at a time when not a lot is blooming.
The flowers age from white to rust in later summer and provide fall color in the garden into winter.
Finally, for intense late summer color, nothing beats California fuchsia, Epilobium canum. There are numerous cultivars available, but my favorite is ‘Catalina', which reaches about 3 feet tall including flowers. California fuchsia will grow in sun or shade but blooms best in full sun. As with the aster, this plant spreads over time, making it a great filler in areas bounded by paths, buildings, or roads. These serve as barriers to keep it contained, while the plant can take the hot conditions often found in these spots.
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.
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.
One great plant that's often overlooked as a choice for the bee garden is flannel bush -- also referred to as California fremontia -- (Fremontodendron californicum). While the species is sometimes available, you're more likely to find one of the cultivars. Look for this plant at specialty nurseries or well-stocked independent garden centers. The species and its cultivars 'California Glory', 'Pacific Sunset', and 'San Gabriel' are quite large, reaching up to 20 feet in height. The cultivar 'Ken Taylor' is more manageable for a small garden; 'Ken' will reach up to six feet tall and 10 feet wide but can be kept smaller with pruning.
Here's why flannel bush makes a great choice for the California (Sunset zones 4-24) bee garden:
1. It's an attractive, eye-catching plant. The large, 3-inch wide flowers cover this plant at peak bloom. You may have noticed large plants along California highways that are covered in yellow flowers come springtime. That's flannel bush...from California Native Plants for the Garden: "A California fremontia in full bloom is an unforgettable sight." This plant was photographed at the Old City Cemetery in Sacramento.
2. Going low water? Flannel bush needs NO summer water, in fact summer water is HARMFUL to this plant. Like many of our California natives, it evolved in hot, dry areas in the absence of the root diseases that are favored by warm, wet conditions. It thus has no defenses against these diseases.
3. Fast growing. Flannel bush grows quickly; you'll have lots of bloom by the second year after planting. This also makes it a good candidate for an espalier. The best cultivars for this are 'California Glory' and 'San Gabriel'. This photo of 'Ken Taylor' was taken one year after planting, at which point is was already about 4 feet across. This cultivar, which is a cross of the Sierra foothills species Fremontodendron californicum decumbens and 'California Glory', has a prostrate form that looks nice on a bank orberm. This is also a great way to provide the excellent drainage this plant needs. Another small (3 feet tall by 6 feet wide) flannel bush is 'Dara's Choice', which was introduced by the Santa Barbara Botanic Garden. It is a cross between Fremontodendron californicum decumbens and Fremontodendron mexicanum.
4. Fun fact for plant nerds....flannel bush nectar fluoresces blue under UV light. Amaze your friends and family with this neat trick! This was first observed by UCD Entomology's own Robbin Thorp many years ago (Thorp, RW et al. 1975. Science (189): 476-478). This property has been observed in many plant nectars and is thought to provide a visual cue to foraging bees (remember that bees see in the UV spectrum).
5. Flannel bush nectar is nutritious. It is rich in isoflavenoids, which may have antimicrobial properties helpful to bees (Scogin, R. 1979. Bot. Gazette (140): 29-31).
We have Fremontodendron californicum and the hybrid 'Ken Taylor' at the Haven. There are also several nice specimens at the UC Davis Arboretum. This plant is at its best in early spring. One note of caution: some people are irritated by the small hairs that cover its leaves. Plan on wearing gloves and long sleeves when pruning.
We know it's fall at the Honey Bee Haven is when our asters come into their full glory. This large (more than 600 species) group of plants even has its own book. Asters recently underwent a taxonomic revision that split the genus Aster into five genera. The commonly-available species either remained in Aster (Old World species) or were moved to Symphyotrichum (New World species).But the common name aster still applies to all. True plant nerds will want to read this detailed summary of the cultivated species. Blooming into November, asters are a valuable late-season source of pollen for bees and nectar for bees and butterflies.
These are the species we have at the Haven, listed in order of bloom:
Aster 'Purple Dome': Symphyotrichum novae-angliae 'Purple Dome'. The species is native to the US east of the Rocky Mountains. This cultivar, which is a UC Davis Arboretum All-Star, is the first aster to bloom at the Haven. It typically starts flowering in late June; deadheading results in several more flushes of bloom until frost. It produces deep purple flowers and stays under 18 inches tall. It will spread and we divide ours every other year.
California aster: Symphyotrichum chilense. This one is about 24 to 30 inches tall; the amount of spread depends on how frequently it is watered. Ours receive a deep soaking about every three weeks and so far we've not seen any invasive tendencies.
Aster 'Wood's Pink':Symphyotrichum dumosum 'Wood's Pink'. This aster has bright pink flowers and is native to the northeastern US. Ours is watered daily. It grows 12-16" tall, making it a nice addition to the front of a border. The species was used as a parent for developing smaller cultivars by Victor Vokes of the UK War Graves Commission, who needed low-growing, late fall color for WWI cemeteries.
Aster 'Fanny's': Symphyotrichum oblongifolium 'Fanny's'. The story of this cultivar of a southeastern US species is that Ruth Knopf of South Carolina acquired the aster from her maid, Fanny, who in turn received it from her grandmother. Fanny is 3 to 4 feet tall and wide.
While entomologists might hope that we select plants for our gardens based only on their value as bee resources, gardeners want attractive plantings. To bridge that gap, here are some suggested plant pairings for the bee garden that not only look good together but also provide complementary bee resources (i.e. one provides pollen and the other nectar) and have similar light and water needs.
Winter and early spring is when our native wildflowers shine. These re-seed easily, so a confined area like a parkway strip is a good place for them; sow seeds in late fall and let winter rains do the rest. If spread to other areas of the garden is a concern, pull these plants while they're still flowering before seeds are set. A great pair for full sun are California poppy (Eschscholzia californica) and phacelia (several species); orange and purple are complimentary colors and always look good together. A pair that can take some shade is Chinese houses (Collinsia heterophylla) and five spot (Nemophila maculata). Their purple and white flowers are an attractive combination; Chinese houses provides nectar and the five spot is a pollen source.
Honeywort (Cerinthe major 'Purpurascens') is an annual that provides both pollen and nectar. Be warned....it re-seeds with vigor! The Haven's plant is well-used by honey bees, and this year it was favored by a California bumble bee (Bombus californicus) queen. It's paired here with foothill penstemon (Penstemon heterophyllus), which covers the honeywort's sparse lower growth and provides nectar. Another spring combination are the California natives seaside daisy (Erigeron 'Bountiful') and California sunflower (Encelia californica). Yellow and purple are a pleasing combination and are colors that are attractive to bees. Both plants provide pollen and nectar.
Yellows and purple continue into the summer. Yarrow 'Moonshine' is a classic Mediterranean garden plant that provides pollen; it's paired here with 'Purple Ginny' sage, but it works well with any of the autumn or little-leaved sages (which are nectar sources). Another summer combination is catmint (Nepeta x faassenii), which provides nectar, and the seaside daisy (Erigeron 'Bountiful'), which provides both pollen and nectar. Both will re-bloom with regular deadheading.
For fall bloom, another yellow and purple combination is bluebeard (Caryopteris x clandonensis) and goldenrod (several species/cultivars). Both are pollen and nectar sources that grow in part shade; goldenrod will spread over time so keep that in mind when selecting a planting location.