Bay Area Plants For Habitat
By Jeffrey Caldwell
I had an occasion to write to a new acquaintance about the culture of plants that appear in my “bee suites” — lists based on numbers of bee species collected on various species of plants on a transect of Californian plant communities where about 70,000 insects were captured on flowering specimens of native and naturalized wild land plants. Many of the best plants for creating insect habitat are among those rarely cultivated by gardeners. The plants on the lists are those that got the most species of visiting bees.
Creating habitat for wildlife has been a constant in my gardening interests; I have also been involved with mitigation plantings and ecological restoration experiments.
I have never owned any land of my own, but worked for decades as a groundskeeper or grounds manager in various settings, besides working as a revegetation technician and planner in various settings, or doing biological impact assessments for roadway work, etc. and then in recent years doing some garden design and working in a few native gardens.
Many of the best plants for creating insect habitat are among those rarely cultivated by gardeners.
I grew masses of goldfields (Lasthenia) and tidy tips (Layia) at Pomona College back in 1971. Unfortunately, it was the driest spring in over 70 years, less insect activity than usual. The horticulturists at the botanic gardens say they won’t viably re-seed unless grown in large masses. Either is pretty easy. Can’t say exactly how yellow rayed lasthenia (Lasthenia glabrata) compares with California goldfields (Lasthenia californica) insect-wise. We grew great masses of it in about 1991 on freshly created areas near the San Francisco Bay, very saline soils — Lasthenia glabrata out-performed everything else in that niche. Unfortunately, I was never able to get out on the site when the masses of it were in flower.
I’ve never had the pleasure of growing bladder parsnip (Lomatium utriculatum) but it is one of the lesser-known native members of the carrot family that historically was quite common and is in cultivation, offered by specialists.
Douglas’ stitchwort (Minuartia douglasii, formerly Arenaria) I have seen at Edgewood County Park, but have not had under much observation. The cultivation information for it in the 1993 Jepson Manual is an indication that its cultivation presents no difficulties. Just another little shiny white flower, I have never seen it offered by any seed producers or purveyors, but it should be easy and the pollinator angle might prove the way to sell it. There are many “easy to grow” native annuals that are in the second or third tier of showiness and thus far have found no market.
Tidy tips (Layia) is actually a major wildflower species that is cultivated and offered, more popular abroad than in this country, a personal favorite of mine. Both it and goldfields, if sown early enough, can be among the very first plants in flower. In their earliest flowering is when they get attention from butterflies. (For the last few years I am writing a book on Californian plants and Lepidoptera). Possibly in their earliest flowering is also when they get most of the bee attention.
Calf lotus (Acmispon wrangelianus) is another obscure little annual. For a while in recent years some of the revegetation oriented seedsmen, Pacific Coast Seed and S&S Seed, were if I am not mistaken, offering inoculated seed of it. I gather there were too few orders, Pacific Coast Seed has pulled way back on the variety of annual legumes and S&S has a reduced variety as well. None of the obscure annual legumes were ever sold retail anywhere to my knowledge. I call this plant “grass of the earth” — historically exceedingly common, part of the general matrix, now mostly lost to endless waves of weeds.
California poppy (Eschscholzia californica), of course, is an enduring staple. Works best for bees when there is a lot of it.
Gold nuggets (Calochortus luteus) are not as difficult to grow as their reputation. Typically favor heavy soils, and not as easy to kill with summer water as most other closely related Calochortus. They are the easiest species of their section of the Calochortus genus to grow, and more people should try them.
Ithuriel’s spear (Triteleia laxa), similarly, is the easiest of its section of Triteleia to grow, easier and more garden tolerant than the Calochortus. More popular in Europe than over here, as with many of our native plants. ‘Queen Fabiola‘ is a famous variety. Another plant that actually likes heavy soils. Especially, more people should try it! All of the native geophytes are relatively under-used compared to their utility and value in every way. Maiden clover (Trifolium microcephalum) is one of the “dropped” legumes that were available inoculated just a few years ago, but apparently didn’t get enough orders to be worth the seed companies continuing to carry them. It is one of the least showy but most ubiquitous species, likely among the easiest to grow, though I’ve never had the pleasure. My hand has barely been in gardening the last several years. It came up a little higher on the number of species of bees known to use it, possibly because the plant simply was present on more of the collecting sites. It is one of the natives that hangs on when much has already gone to weeds. (In restoration, the last to go are among the first to consider for putting back).
At the present time, being offered wholesale are foothill clover (Trifolium ciliolatum), clammy clover (Trifolium obtusiflorum), tomcat clover (Trifolium willdenovi), and Spanish clover (Acmispon americanus), among the obscure native annual legumes — all, no doubt, good choices for bees. Spanish clover is tops for butterflies!
Naked buckwheat (Eriogonum nudum) is not as large or showy as some of the Eriogonum species more commonly used in gardening, but is easy enough to grow. It is unsurpassed as butterfly caterpillar forage. It is proving very easy and long-flowering for one of my butterfly-gardening clients, volunteering a bit; also working fairly well for Acterra in a Mountain View planting for Google, Inc. on the banks of a grass-lined channel levee. It also will tolerate very heavy soils well.
Hayfield tarweed (Hemizonia congesta luzulifolia) is one of the wildflowers still hanging on in many otherwise weed-infested situations. In recent years it has been offered by Larner Seeds, a major wildflower seed purveyor. Valuable for late-season flowers. I haven’t grown it but suspect it is easy.
Brittle leaf manzanita (Arctostaphylos crustacea) honestly is not generally cultivated. Probably not perceived to be as handsome as the species which are more commonly cultivated. Likely was the most common manzanita in the areas where Moldenke collected his approximately 70,000 flower-visiting insects. It is the most common manzanita in the Santa Cruz Mountains. In garden usage in the lowlands, others are probably equally good for bees.
Buck brush (Ceanothus cuneatus) is easy to grow. There are even some nice blue selections, though most are white. I think the foliage and form are handsome too; but many of them, flower-color wise, are some sort of white, not terribly exciting to many; but great plants for the bee-lover. (I’ve had a grand total of one client focused on attracting bees; we planted a couple in her front yard, sandy soil in Saratoga, where they worked quite well.) I believe it is one of the more culturally tolerant species in the genus, great for low maintenance. Best planted small. A problem with Ceanothus is that they grow fast, quickly becoming root bound in containers.
Hollyleaf cherry (Prunus ilicifolia) is one of the easiest and most adaptable of all natives; even tolerates shearing quite well. Can be a nuisance with zillions of volunteer seedlings (nothing is ever perfect, says the Little Prince). Tolerates heavy soils well, almost any cultural treatment. Best and most satisfying to grow by planting a seed where you want the plant. You will have the biggest and healthiest plant that way in four years, even less. Enables the plant to send down a great taproot. A top honeybee plant and other bees and bugs love it, too.
Golden yarrow (Eriophyllum confertiflorum) is a staple revegetation item, not used so much in gardens. A perennial that could be grown by seed sown en situ. The large number of bees collected may partly be a reflection of its commonness on Moldenke’s collecting transects. Easy in gardens but may rot in wet winters; too much moisture and cold not good for it. (Get great opinions on native perennials from Glenn Keator’s book). Gumweed (Grindelia hirsutula) is easy to grow; have planted it in two client’s gardens. May take awhile to establish, probably especially good to plant it early in the fall. Have not been able to plant a mass of it anywhere yet. (My suites are theoretical more than anything, though all my observations and experience tell me to expect them to work fairly well). This and so many other natives might work best from seed en situ — not a way much of anyone works anymore, but, in my limited experience, a most satisfying way to garden.
Yerba santa (Eriodictyon californicum) has a disease problem which has kept it out of most gardens. In field observations of butterfly usage, it is second only to California buckeye (Aesculus californica). Other species in the genus might be substituted — they are a handy size for most gardens; the other species do not have the disease problem. They are simply not terribly showy, but certainly of useful sizes and shapes and deserve a place in more gardens. Wonderful for those interested in insects.
Pitcher sage (Lepechinia calycina) is another easy-to-grow native, very handy size, relatively easy culture shrub. Not as super-showy as other plants that have taken first place. More than the bees, what I’ve noticed is beautiful beetles in their flowers. Many of these plants are great for the masses who really aren’t gardeners. Easy care. Farewell-to-spring (Clarkia amoena) has got to be one of the greatest under-used species. Very easy, very hardy, somewhat snail-resistant. In a trial of about 50 wildflower species, I found it one of the easiest, and it is one of the showiest, growing taller than many. There may likely be a whole different spectrum of bees in the suburbs, so the numbers attracted may vary widely from wild lands. This plant can provide a lot of delight for little work. I suspect it would naturalize on many sites. (I not only have not had any land of my own, I’ve had to move many, many times. I’ve probably moved more times than any man my age you know. I did a big test when living in downtown San Jose, spring of 2005, I think it was.)
Coyote mint (Monardella villosa) is pretty much of a staple native perennial. Fairly easy and reliable, grown by many, a great plant for the butterfly garden.
Bush mallow (Malacothamnus) is another handy-sized shrub for many yards. Fairly garden tolerant though extreme over-watering can put it down.
Deerweed (Acmispon) is rarely used in gardens, but commonly in revegetation. Easy to grow. Working fine in that planting at Google. Also great for butterflies, good host and nectar plant, works even better in southern California. Good choice for the insect-lover. Toyon (Heteromeles arbutifolia) is a staple native plant, wonderful for insects when in flower, including honeybees, but a vast spectrum. Fruits feed about 20 species of birds, too.
Hairy bird’s-beak (Cordylanthus pilosus), lies pretty much beyond what anybody has worked with, horticulturally. Good choice for anyone interested in breaking new ground. Would have to classify it as “interesting”. Hardly showy enough for anyone to notice, but the bees do.
California figwort (Scrophularia californica) is actually “easy” — a perennial with small seeds that, nevertheless, is not difficult to get going by simply spreading a few seeds. Also works fine from containers and is somewhat offered. Culturally tolerant, no need to know or do anything special to grow it. Perhaps if it found a place in more gardens the common Checkerspot butterfly would move into the suburbs. Buckeye caterpillars eat it, too, and hummingbirds are among the flower visitors.
Rigid hedge-nettle (Stachys ajugoides) is easy. Some came up in a small, confined bed at the world headquarters of American Microsystems, Inc. I allowed it to take over the bed. A plant that improves with cultivation.
Basically like a mint. When it gets ratty, cut it back. With such garden care — irrigation and dead-heading or renewal pruning — it will flower over and over again. Modestly attractive, relatively little work.
Jim-brush (Ceanothus oliganthus var. sorediatus) is likely one of the more garden-tolerant Ceanothus, sometimes sort of a riparian Ceanothus, a plant of the outermost edge of the riparian zone. Fross and Wilken, top experts, say: “Although used sparingly today, hairy ceanothus (Ceanothus oliganthus) was cultivated frequently in California in the past and has performed well in a broad range of garden conditions. Tolerant of heat, clay soils, and some summer watering … fast-growing and vigorous, light pruning will help moderate its robust nature … partial shade as well as full sun”.
Western morning-glory (Calystegia occidentalis) is easy to grow; I propagated some myself decades ago. Useful as being a rather small vine which can be allowed to grow up into a shrub without overwhelming it. Creates great little niches for small birds to nest. Ocean spray (Holodiscus discolor) is one of the under-used plants. Super for insects, especially if grown in the sun. Problem, for some: it is deciduous. But deciduous plants are often best for habitat value. Also typically very tough and adaptable. I found a photograph of one used in an Agi Kehoe garden in full sun with other natives, in full bloom, quite striking.
Yerba buena (Clinopodium douglasii) is a staple small-scale native ground cover. Easy. Culturally tolerant, works best for insects in the sun, not drought-stressed.
Western vervain (Verbena lasiostachys). Very easy, may need a fair amount of attention to pruning and deadheading. Other verbenas might well better for many gardeners. Among the best for butterflies.
White plectritis (Plectritis macrocera) another third-tier of showiness wildflower, valerian family. Some plectritis is being grown, I think, by Oregon butterfly gardeners. Not very showy but probably easy. Bugs being a reason to grow it.
Saltmarsh baccharis (Baccharis glutinosa) is extremely easy, grown for revegetation. Might take over your yard, if you water a lot. Some of the best insect plants need root containment. Now they have products for taming running bamboos, should work fine for overly vigorous perennials. Moldenke captured 120 species of insects on its flowers! One of my clients grows it in a very large container. Super for insects.
California buttercup (Ranunculus californicus), extremely easy, grass of the earth. Flowers a very long time. Often see nothing on it, then it is mobbed. I think it is a strong secondary player for the pollinators. Other plants may out-compete it for attention, but when they pause, it is there for the bugs to fall back upon.
Narrow leaf milkweed (Asclepias fascicularis) has found a market with butterfly gardeners. Spreads readily underground, tough and easy, not terribly showy but quite popular with insects, especially butterflies. This and other milkweeds come up late in the spring, sometimes people think it is dead or forget that it is there when dormant. As a rule, “common” plants are easy to grow. Not as showy as some, but often better serving the needs of the insects.
They didn’t come up in these particular suites, but some common wildflowers are great for bees. One of the best is “beefood”, lacy phacelia (Phacelia tanacetifolia). A large mass of it under a flowering leguminous tree was quite delightful and got a huge number and diversity of bees to the Saratoga bee garden. It is probably the easiest of the true annual wildflowers (California poppy is not actually an annual).
One rarely grown here, commonly abroad, is meadowfoam (Limnanthes douglasii). It is actually sort of a vernal pool plant, happy being well watered.
Chinese houses (Collinsia heterophylla) are easy and got a few interesting bees in my wildflower trial in San Jose (somewhat spoiled by being the coldest spring in memory!)
Jeffrey Caldwell is a member of the CNPS East Bay Chapter and a Horticultural Consultant Specializing in Native Plants and Habitat Gardens.