Cliff paintbrush (Castilleja rupicola) COSEWIC assessment and status report: chapter 8

Biology

General

Little information is available on the biology and ecology of Castilleja rupicola. Only basic reproductive facts have been compiled about the genus.

Reproduction

It is believed that most, if not all, Castilleja species require cross-pollination to set seed. According to Duffield (1972) and Pennell (1948), many species appear to be pollinated by hummingbirds, and bees may be important pollinators of other species (Bauer 1983, Duffield 1972). The average number of seeds produced by an individual is not known although Sheenan and Sprague (1984) report that it is not uncommon to observe more than 100 seeds produced by a single capsule. Seed production is likely to be of critical importance to Castilleja rupicola because it does not appear to be capable of reproducing by any other means.

Only a few gardening enthusiasts have experimented with Castilleja propagation by seeds. The process, although sometimes difficult and never a certainty, can meet with some success following a few general rules. Guppy (1997) placed seeds in a refrigerator and attained germination in one to four months. During this time young plants of potential host plants are potted in sandy soil. When the Castilleja seedlings have unfolded their seed leaves they are ready to place in the host pots, eventually thinning to about three per pot. A plastic tent, to retain moisture, will be required until the seedlings are well established. Field survival of these seedlings may not be successful with subalpine/alpine species, either at low or high elevations.

Survival

Unknown.

Physiology

Unknown.

Movements/dispersal

Castilleja rupicola depends on seeds for reproduction. Local dispersal is likely effected by winds shaking the seeds out of the capsules and possibly by birds and small mammals similarly promoting the scattering of the minute seeds. Rescue from adjacent populations in Washington State is highly unlikely due to the localized dispersal mechanism and the long periods of time likely required for this species to disperse over distances of many kilometres.

Nutrition and interspecific interactions

As with other species of Castilleja, it is likely that C. rupicola is a facultative parasite on the roots of other species. (See “Habitat requirements, for a list of possible host species.) Heckard (1962) investigated the growth of eleven species of Castilleja with and without hosts. All plants are capable of completing their life cycle in the absence of a host. However, when they are grown in culture with other species, all but one Castilleja species exhibit faster growth rates, produce a larger number of branches, and flower earlier than when grown in isolation. An examination of the roots indicates that Castilleja species form haustoria with the roots of other plants, including other Castilleja plants (although they exhibit reduced vigour when grown with members of the same genus). Pscheidt et al. (2003) indicates that leguminous plants have been shown to be more beneficial hosts than grasses.

Behaviour/adaptability

Unknown.

Page details

Date modified: