For a long time, I thought that castillejas were practically ungrowable in gardens because I had been told they were parasitic plants. This belief was reinforced by many books on the subject. The third edition of Gardening With Native Plants of the Pacific Northwest, published 2019, states that gardeners who grew castillejas must be “just plain lucky” because their seeds “must germinate in the proximity of roots of other plants” (p. 249). As I will show in this article, castillejas do not require being in proximity to the roots of other plants to germinate. At some wholesale nurseries, they are germinated, grown, and sold in the thousands without the presence of hosts in their pots. See the offerings of Seven Oaks Native Plant Nursery, a wholesale nursery in Albany, Oregon. Seven Oaks has been offering Castilleja miniata for many years and often has in excess of 300 plants available at a time, all grown in individual pots, without a host.
It was only after I saw them offered for sale by a few native plant nurseries that I realized that growing these beauties in my garden was an achievable goal. I have learned that castillejas are not true parasites. Rather, they are what is called hemiparasitic, meaning that they make their own chlorophyll and can live on their own without a host, but that they also have special roots which can attach to the roots of a host to obtain additional water and nutrients. They have this in common with some other members of the Orobanchaceae family, in particular with members of the genus Pedicularis which I have also been growing in my garden.
I first obtained some castillejas about seven or eight years ago from a local native plant nursery. I purchased three Castilleja miniata plants, and, as it turned out, this was a good species to start with. Sometimes called common paintbrush or scarlet paintbrush, this is a very widespread species, growing in varying habitats over its extremely large range. I have seen this species growing right at cliff’s edge by the Strait of Juan de Fuca, in wet meadows in the Central Cascades in Oregon, by the millions near Johnston Ridge, Mt. St. Helens, on dry volcanic soils, and along roadsides near Chinook Pass in Mt. Rainier National Park.
According to the Burke Herbarium of the University of Washington, this species occurs throughout much of the Pacific Northwest from Alaska south to California, east to the Rocky Mountains in the United States, and east to Ontario in Canada. It is fairly clear from the wide range of this castilleja that it can grow in very wet soils as well as in very dry ones.
When I got my first plants of Castilleja miniata I was unsure where to plant them, but after doing some research it appeared that they were not picky about hosts. That fact has been borne out by all my subsequent experience with castillejas. People seem to obsess about the correct host to plant castillejas with and then never get around to planting them. My advice: just plant them, preferably in conditions that mimic as closely as possible their natural habitat, about a foot from just about any other plant. As the castilleja and host grow, their roots will connect. Don’t plant too close to the host. I have lost more castillejas as a result of their being overwhelmed by their host than by their being too far from it. And, of course, once you get castillejas to self-sow, just let nature take its course and don’t worry about host plants.
I planted my first three Castilleja miniata plants around a Stipa gigantea (syn. Celtica gigantea). They did well there. It was a fairly dry spot, but they have self-sowed in subsequent years all around that original planting. I do not know if my original plants are still there, but there are plenty of their progeny about. Too many to count, in fact.
Because of the vagaries of my sprinkler system, some of these are now growing in quite moist soil, while others are in very dry spots. I have to say, though, that while Castilleja miniata can and does grow in dry soil, it grows more plentifully in moist conditions and I have killed more castilleja seedlings from lack of water than from any other cause. This may have to do with a theory that one reason castillejas tap into their host is to obtain water, so castilleja seedlings starting out on very dry soil must quickly find a host or they will die from lack of water. This may hold even for those castillejas that come from very dry habitats.
After I got those first three castillejas, I discovered a wholesale source for Castilleja miniata, so naturally I bought several flats of them and planted them in numerous parts of my garden. The fact that these can be grown by wholesalers gives a clue that they are growable, and not just in small quantities. I should also add that I have since learned that a number of growers produced mass quantities of several different species for revegetation efforts for Puget Sound prairies, including Castilleja miniata, C. hispida, and C. levisecta. Castilleja levisecta, also known as the golden castilleja, was endangered in Washington State, and extirpated in Oregon, so a breeding program along with extensive research was undertaken. Vast quantities of this castilleja were propagated, and much was learned in the process. This program was successful. Today this castilleja is off the endangered list, and there are robust populations in Oregon and Washington.
Several things were learned in the course of bringing Castilleja levisecta back from the brink. First, castillejas do not require host plants to be grown from seed. Hosts are not required for germination, nor are they required for growing these on, at least for a year or two. I have grown castillejas in pots for as long as four years without a host. As long as they are well fertilized and watered, they do quite well, and they flower. There are studies showing that castillejas with hosts do better in the long run, but it is certainly not necessary for them to have hosts.
A second takeaway from all the studies on Castilleja levisecta was that these set much more seed if there were other plants and populations for them to breed with. I think it is reasonable to assume that the same may apply to other species of castillejas as well. In other words, if you want castillejas to self-sow and naturalize in your garden, it is best to have more than one of a species. In fact, the more is probably the better. The fact that I started with so many plants may go a long way to explain why I have been successful with getting them to naturalize in my garden. So my advice is, if you are buying castilleja plants, try to buy more than one at a time. See Beth A. Lawrence’s thesis entitled Studies to Facilitate Reintroduction of Golden Paintbrush (Castilleja levisecta) to the Willamette Valley, Oregon, presented on December 12, 2005, to the Department of Botany and Plant Pathology, Oregon State University: https://appliedeco.org/wp-content/uploads/Lawrence_Thesis_CHAPTER-5-Grow... This brings up another point about growing castillejas. If you have more than one species in your garden, you are likely to get hybrids. Castillejas are notorious for hybridizing.
Growing from seed
I have been growing castillejas from seed for a number of years, and I learn more with each succeeding year. I have tried growing all castilleja seeds that I can get a hold of: so far, I have tried at least 17 different species and I have successfully germinated all that I have tried, eventually. All the species I have tried have done best if sown in the winter, no later than the end of January, and for some, even earlier is better. Ones that are from high elevations seem to need a longer period of cold stratification, which is understandable considering their natural habitat. I have also found that castillejas that do not come up the first year after sowing will often come up the second year. So, as everyone should know by now, pots of seeds that did not come up the first year after sowing should not be thrown away.
I do all of my seed sowing outside on my deck. I leave pots outside for the winter. I do not have a cold frame, but I live in Zone 8 on the Olympic Peninsula where it doesn’t get all that cold compared to other parts of the country. I use a cactus mix for sowing all my castilleja seeds. I sow the seeds on top and then cover with a thin layer of poultry grit. I like the cactus mix because it is well-drained and doesn’t seem to grow much in the way of mosses and liverworts (although it does eventually grow them). The grit also helps with that, but not one hundred percent. This last year I had some seed of Castilleja parviflora var. oreopola (aka magenta paintbrush) from near Mt. Rainier. I sowed some in the cactus mix and some in regular potting soil as an experiment since in the wild this paintbrush grows in fairly moist rich conditions. I saw very little difference in germination, except perhaps the seed sown in regular potting mix did a little worse. If I didn’t have a good quality cactus mix available, I would probably make a custom mix with a regular starting mix, sand, and grit. In other words, a standard mix for most alpine or dryland plants.
Most castillejas start germinating in the spring. It seems that those from the warmest climates usually germinate first, understandably. This last year Castilleja parviflora var. oreopola was last to germinate. Others that I have germinated include C. angustifolia var. dubia (syn C. chromosa), C. applegatei, C. arachnoidea, C. exserta, C. hispida, C. integra, C. lineariifolia, C. miniata, C. oresbia, C. parvula var. parvula, C. peckiana, C. rhexiifolia, C. scabrida, C. sulphurea, and C. thompsonii. Germinating these does not necessarily mean that I have gotten all these species established in my garden. Often, a whole seed pot will only produce one seedling. Even if more are produced, there are often large losses in potting the seedlings on. I have concluded that it is best for most of these to either leave the seedlings until their second year before potting them on, or to direct sow the seeds in the garden. Castilleja miniata, C. hispida, C. lineariifolia, C. exserta, C. integra and C. angustifolia var. dubia (syn. C. chromosa) are particularly good candidates for direct sowing. If direct sowing, it is important to have some bare soil in the garden to sow them into, or a loose mat-forming plant like Monardella macrantha ‘Marian Sampson’. Loose mat-forming plants catch the seeds and provide a host, while simultaneously allowing the castilleja seedlings some light. I often see castillejas growing in loose mats of other plants in the wild. It is also imperative that one can recognize the seedlings. The image above shows what these seedlings look like, more or less, though exact appearance differs from species to species.
In general, the different species look similar to each other at the seedling stage. And if you have a landscaping service, forget about it, since most landscapers are bound to weed out all the seedlings. Finally, I should mention that castilleja seedlings should not be allowed to dry out, as that will surely kill them. This goes for desert species as well as species from wetter areas. As mentioned above, until castillejas attach to a host, it seems they are particularly sensitive to lack of water.
Castilleja exserta is a particularly good species to grow from direct sowing. This is an annual castilleja from California and the southwestern United States. It is very beautiful, especially en masse as it is sometimes seen in the wild. This species has done well with direct seeding in my garden and even perpetuated itself by self-sowing for several years. Recently I did another direct sowing, and it did well from that again. This is a species that I would only direct sow, into an open area in the garden, preferably on lean, well-drained soil.
I now have castillejas growing everywhere in my garden. I have too many to count, and their numbers increase every year, from both self-sowing and more direct sowing by me. Most of the castillejas in my garden are orange or scarlet. Currently, I am working on getting some of the pink ones to naturalize. These include Castilleja parviflora var. oreopola, C. parviflora var. olympica, and C. rhexiifolia. Others I would particularly like to obtain are Castilleja hispida var. acuta, Castilleja thompsonii (a yellow/green species common in eastern Washington), and Castilleja schizotricha. I have seen some purple-colored castillejas, and those are also on my list to obtain.
The main problem with growing castillejas is obtaining seed. There is no seed commercially available for the vast majority of castilleja species. Fortunately, the NARGS seed exchange often has various species available. Other sources include Western Native Seeds, Alplains, Geoscapes Desert Nursery, Northwest Meadowscapes, Inside Passage Native Seed, Larner Seeds, Plants of the Southwest, Miss Penn’s Mountain Seeds, Native Seed (Texas Native Seed), Jelitto Seed, and the San Diego Chapter of the California Native Plant Society. Most of these sources carry only a few species.
My takeaway after growing castillejas for the years that I have is that they should be treated as any other plant. They can be sowed and will germinate like so many other native plants, without any special considerations for the fact that they are hemiparasitic. They can be planted out like most other plants, with the caveat that each of them should be somewhat close to another plant, but what species of plant is not all that important. They can be allowed to self-sow like any other native plant. They can even be dug up and moved like any other plant, an operation I have successfully done on more than one occasion. And finally, they can be direct-sowed like so many of our natives.
I have enjoyed my adventures with castillejas. I think you would enjoy similar adventures in your own garden.
For a fairly comprehensive collection of pictures and descriptions of the species of castillejas, I recommend Mark Egger’s Flickr gallery of the genus Castilleja, https://www.flickr.com/photos/mark_egger_castilleja/collections/72157617...
