by Art Guppy
Art wrote several articles about Castilleja, which were published in two 2005 issues of the Alpine Garden Club of BC Bulletin and others in BEN (Botanical Electronic News).
As garden plans, Castilleja tend to suffer from bad press.
One reads that they are difficult or even impossible to grow. Don’t believe it. Some even survive in my garden, which proves they are very tough plants.
That does not mean that all Castilleja are easy to grow. As with any genus of plants, those from a high altitude or a very different climate are likely not to adapt to our coastal gardens.
I recommend three species that grow naturally near where we live.
Castilleja miniata is aptly called the Scarlet Paintbrush, though very rarely it is yellow or orange. It is often seen in slightly moist places on sandy or rocky slopes above our sea beaches. In such locations it can usually be identified by its tall, branching habit and fairly narrow leaves that lack lobes or teeth except right under the inflorescence where the leaves grade into the lobed bracts which enclose the flowers. The species is widespread over much of western North America, but plants raised from seeds from away from the coast may not adapt to our gardens.
Castilleja hispida is often called Harsh Paintbrush, but don’t expect it to be harsh. Apparently sometimes the leaves are hispid, which means having firm, coarse hairs, but that condition seems rare. Usually the leaves are so sparsely hairy to villous with soft hairs. Let’s call it the Soft-harsh Paintbrush. It is the fairly common red paintbrush of the rocky hills of southern Vancouver Island, and generally has wide leaves with one or two hairs of lone, slender lobes. Young shoots may have narrow, unlobed leaves. The species is widespread and high in the Cascades is often yellow.
Castilleja levisecta, the Golden Paintbrush, is a delightful clear yellow and could well be considered the most beautiful of all Castilleja. In B.C. it grows in the wild only on Trial Island and one other small island, and in Washington State is so rare as to be considered endangered. It grows wild nowhere else, though it used to be in a few locations in Oregon.
Castilleja are hemiparasitic; that is, they attach to the roots of other plants and obtain part of their water and nutrients from those plants. It is notable that the above three species could be grown without host plants if they were given ideal conditions with adequate water and nutrients, but in the hard, cruel world of the garden, with drying winds and competition from other plants, they would not live long without the help of water and nutrients stolen from host plants.
For the gardener, the providing of suitable host plants is the most difficult problem connected with the growing of Castilleja. A host plant must be vigorous, or the parasite will kill it, but it must not be too weedy or the gardener will not tolerate its presence. It must suit the taste of the Castilleja, and the gardener can only learn what plants are acceptable to the parasite by observing and experimenting. It is of very great importance that the host plant have roots close to the surface, as like most parasites, Castilleja are lazy and will not make the effort to reach down to the deep roots.
Observation may enable you to learn what hosts Castilleja choose in nature, and you can experiment to find other suitable hosts. You will find C. miniata plants growing with alder and willow, but you will find them with these hosts only where rock, hardpan, or other soil conditions keep roots close to the surface. I have grown C. miniata on Oemleria cerasiformis (Indian-plum), but after a few years the Oemleria suddenly died. It was a large shrub so it seems unlikely the Castilleja killed it, but something did. At the present time I have a self-sown C. miniata doing quite well apparently on Rubus parviflorua (Thimbleberry).
An experiment that I tried twice, and that seemed very successful at first each time, involved growing C. miniata on a seedling alder in a large pot so the host’s roots could not grow out of reach of the parasite. Each time the Castilleja did extremely well for two years and produced a magnificent display of bloom, but each time the alder died at the end of the second year, and the following year the Castilleja died.
If you are not a purist, and don’t mind using a non-native host, C. miniata does very well with Spiraea japonica, especially if the soil is shallow. At one time I had C. miniata with close to 100 inflorescences (too many to count accurately) growing on Spiraea japonica in about 8 inches of soil over rock, but I lost it when I forgot to water it. C. mininta demands plenty of water.
On the rocky hills of southern Vancouver Island, one often finds C. hispida growing on either Holodiscus discolor (Oceanspray) or Symphoricarpos albus (Common Snowberry), but apparently only where rock keeps the host roots close to the surface and where there is seepage water until late spring. Both natural hosts may seem a little large for use in a garden, but Symphoricarpos hesperius (Creeping Snowberry) is an excellent substitute and has the added advantage of producing roots close to the surface. It can creep about with excessive exuberance, but carrying a paintbrush or two slows it down considerably so that a little clipping of long shoots in the spring will make it entirely docile. Like C. miniata, C. hispida will accept Spiraea japonica as a host.
C. levisecta in nature probably usually grows on rhizomatous grasses, but likely also attaches to Eriophyllum lanatum (wooly sunflower). The latter seems a good host for use in the garden as it is an attractive plant which flowers as the paintbrush’s flowering period ends. Unfortunately the paint brush sometimes does too well and kills the host. Then one must rush to insert young host plants close to the parasite. Usually small rooted shoots of Eriophyllum are easily obtained where the species grows well, as in my gravel driveway. C. levisecta also does well on Creeping Snowberry.
To be continued. The next part will have a little about pollination, but will deal mainly with growing from seed and from cuttings of small shoots taken in early March.