Castilleja septentrionalis Lindl.
Basis for Listing
Castilleja septentrionalis (northern paintbrush) occurs in boreal and subarctic regions of northeastern North America, and in alpine regions of the Rocky Mountains. It was discovered in Minnesota in 1891 at a single location on the shore of Lake Superior near Grand Portage. Despite intensive searching by botanists, the species has been found only twice since then, once in 1991 and again in 1999. The newly discovered populations are also on the shore of Lake Superior (North Shore Highlands Subsection), and only a few miles from the original site. Castilleja septentrionalis remains one of the rarest of Minnesota's subarctic, disjunct species, and it was listed as state endangered in 1996.
Castilleja septentrionalis can be distinguished from the common and closely related C. coccinea (Indian paintbrush) by having pale yellow bracts rather than bright orange-red bracts on the flowering stem. There is another related species in Minnesota, C. sessiliflora (downy paintbrush) that occurs only in prairie habitats. Castilleja septentrionalis is positively identified by having uncleft leaves and bracts (at most, the bracts have 1-3 small teeth). The flowering stems are generally over 20 cm (7.9 in.) tall, branched or unbranched, and the flowers are arranged in dense terminal spikes.
In Minnesota, this subarctic species is known to occur only along the shore of Lake Superior. It grows on thin soil among boulders or on fractured bedrock. Common associated shrubs and forbs include Alnus incana ssp. rugosa (speckled alder), Spiraea alba (white meadowsweet), Dasiphora fruticosa (shrubby cinquefoil), Primula mistassinica (Mistassini primrose), Scirpus spp. (bulrush), and Carex spp. (sedge). The plants occur close enough to the lake to occasionally receive water spray from waves, but protected enough that the wave intensity is moderated.
Biology / Life History
Castilleja septentrionalis is a perennial forb. Like other members of the Castilleja genus, it is hemiparasitic on other plants; that is, it must be attached to the roots of another plant (not host-specific) for full development. In Minnesota, it’s composed of mostly flowering shoots, but vegetative shoots are also present. Flowers, as is typical for the genus, seem designed for insect pollination, being relatively large, over 1.5 cm (0.6 in.) long, and having a colored bract. It is not known how long a given plant or patch of plants persists in a given locale, or what microhabitat conditions are required for the survival of this subarctic species in Minnesota.
Conservation / Management
A portion of the site where C. septentrionalis is known to occur is on State Forest land and the other portion is on privately owned land. Even if the site is protected from development, the rocky habitats remain vulnerable to inadvertent disturbance from recreational activities. The most beneficial conservation measure may be to increase awareness of the fragility of rare features on Minnesota's rocky landscapes.
Best Time to Search
The best time to search for Castilleja septentrionalis is when it is in flower from mid-June to mid-August.
Conservation Efforts in Minnesota
A thorough inventory has been accomplished by the Minnesota Biological Survey (MBS) in northeastern Minnesota for rare plants, which is a great contribution to conservation. The results of the survey form a sound basis for developing a conservation plan. The State Forest land harboring this species has been recommended by the MBS for protection as a natural area, but no official action has been taken as of 2020.
Welby R. Smith (MNDNR), 2020
(Note: all content ©MNDNR)
References and Additional Information
Butters, F. K., and E. C. Abbe. 1953. A floristic study of Cook County, northeastern Minnesota. Rhodora 55:21-55.
Given, D. R., and J. H. Soper. 1981. The arctic-alpine element of the vascular flora at Lake Superior. National Museums of Canada, Publications in Botany No. 10, Ottawa, Ontario. 70 pp.