Castilleja coccinea, Indian Paintbrush – 8 (1)

By Paul Heydon

A number of years ago, while hiking on the Carden Alvar north of Toronto, I stumbled across a stand of Indian paintbrush (Castilleja coccinea). It was one of the most breathtaking scenes I have experienced: a sea of brilliant scarlet, orange and yellow. I now go back every year to see the show.

Indian paintbrush is a terrestrial herb or flowering plant found on alvars, moist meadows, prairies and open woods. At Carden it grows on thin, moist soils over limestone bedrock. Cattle graze the meadow, preventing shrubs from overtaking the flowering plants. Some of the associated species growing with it are balsam ragwort (Packera paupercula), little bluestem (Schizachyrium scoparium), wood lily (Lilium philadelphicum), hairy beardtongue (Penstemon hirsutus), prairie smoke (Geum triflorum) and blue-eyed grass (Sisyrinchium montanum). When combined with Castilleja coccinea, they offer a varied palette of scarlet, orange, blue, pink and yellow from spring through summer.

Indian paintbrush does not perform well in shade and is typically found on sub-acid to slightly alkaline soils. Its range extends from the Missouri River west into Kansas and Oklahoma, and north into portions of Saskatchewan, Manitoba and Ontario. In Ontario 50% of Indian paintbrush’s elemental occurrences are found on alvars.

Castilleja coccinea reaches heights of 60 centimetres (two feet). The leaves on the flower stalk are shaped like birds’ feet. The basal leaves are either three-lobed or entire. The flowers are perfect (they have both pistillate [female] and staminate [male] parts), inconspicuous, in a dense terminal spike, irregular, 2.5 centimetres (one inch) long, and borne in the axil of the bract. The three-lobed bracts with showy scarlet tips provide the spectacle. The species name coccinea means scarlet although sometimes the bracts are yellow and look like their ends have been dipped in paint, hence the common name paintbrush. It’s the bracts, not the inconspicuous flowers, that attract pollinators such as hummingbirds. Flowering takes place from May to August. The fruit is a small capsule producing hundreds of small seeds. Botanists do not know how the seed is dispersed.

Most taxonomists place Indian paintbrush in the figwort (Scrophulariaceae) family. Others place this plant in the broom-rape (Orobanchaceae) family due to shared molecular features. Indian paintbrush is primarily a biennial, although sometimes it can be annual, producing a basal rosette the first year and flowering stalk the second year. The plants die shortly after seed set.

Indian paintbrush is a root hemiparasite, which means it is partially parasitic, acquiring some of its water and nutrients from haustorial connections with a host plant. Haustoria are specialized absorptive organs that invade the roots of host plants. Haustoria are formed in the root system of Indian paintbrush and development is signalled by molecules exuded by the host plants, allowing the roots to become partially heterotrophic. The rest of the resources are produced from autonomous photosynthesis. Many hemiparasitic plants have much higher transpiration rates than their host which enables them to divert the flow of resources from their host. I have grown Indian paintbrush without a host but the plants were less vigorous. Indian paintbrush has a broad host range although some scientists found that it performed better with certain hosts. Hosts differ in quality of resources such as nutrition and defensive secondary compounds that could be transferred to the parasite.

In the wild, Indian paintbrush usually germinates in early fall. In cultivation they germinate after two–three months of moist/cold stratification. I put seed in a labelled Ziploc bag with just enough moisture to prevent the seed from drying out and place it in the refrigerator at 2-5˚ C (35-41 F). The first year I did this the seed rotted. To remedy the problem I put sulphur, a natural fungicide, in with the seed. In the spring I sow the seed on any suitable germinating media. Usually more than 50% of the seed germinates. When seedlings form a rosette with five or more leaves I tease them out and plant them into the garden beside other plants or into 10-centimetre (four-inch) pots with a suitable host such as balsam ragwort, prairie smoke, hairy beardtongue or little bluestem. Do not let them dry out! In my limited experience Castilleja coccinea does not self-sow into gardens; I have to plant seedlings every year.

Besides its appeal to pollinators, Indian paintbrush is wonderful to have in a garden since flowering continues throughout the growing season (if there is ample moisture) providing gorgeous colour.

Paul Heydon is a biologist/ecologist who owns Grow Wild Native Plant Nursery and Paul Heydon Biological Consulting. He loves exploring the natural world.