Native Plants Journal 6.1 (2005) 62-68
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Propagation Protocol For Indian Paintbrush
PO Box 447
East Glacier Park, MT 59434
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Castillejaangustifolia, applegatei, cusickii, exilis, hispida, indivisa, integra, linariifolia, lutescens, miniata, minor, nivea, occidentalis,pallescens, pulchella, purpurea, rhexiifolia, scabrida, sessiliflora, sulphurea, seed propagation, hemi-parasitism, stratification
USDA NRCS (2004)
Indian paintbrush (Castilleja spp. Michx. [Scrophulariaceae]) is a vibrant, beautiful genus of annual, biennial, and perennial wildflowers that are found exclusively in North America. The majority of species grow in the West, but a few species occur in the central portion of the US. There are more than 150 species and many freely hybridize with one another in areas where their ranges overlap. They are found in a wide range of habitats, ranging from low elevation wetlands and riparian areas to dry grasslands, steppe-shrub communities, and rocky slopes to mid- to high elevation mountain meadows and slopes.
The inflorescence is a short or elongate terminal spike bearing tubular-shaped flowers that are subtended by numerous colorful bracts. Indian paintbrush is appropriately named as the bracts graduate in color from green leafy stems to the brightly colored tops of the inflorescence, thus giving the appearance that the tops of the plants have been dipped in paint. Both insects and hummingbirds are attracted to these plants and serve as pollinators.
The flower and bract color, even within a single species, can range wildly across the color palette from rich reds, scarlet, and fuchsia to orange, salmon, pink, yellow, and cream. It is not unusual to find a single flower with up to 3 contrasting colors on the showy bracts. Because the floral bracts make up most of the color, they tend to remain showy for several weeks through the growing season. The rich, brilliant, prolonged color of these species is one reason why they are some of the most desired native species for the home landscape, yet they are not widely available for sale as container plants because of their interesting biology.
Paintbrush species, as well as some other genera in the figwort family (Scrophulariaceae), have a unique biology known as hemi-parasitism. Unlike a true parasitic plant, hemi-parasites are capable of manufacturing their own food and obtaining water and nutrients from soil, but they also form specialized roots known as haustoria roots that attach to the roots of a host plant, thereby providing additional water uptake for the paintbrush plant and possibly some organic and inorganic nutrients. This relationship does not kill the host. Seeds do not require a signal from the host to initiate germination, and they contain endosperm that provides enough energy for the seedling to establish independently (Press 1989). Unless a haustorium root becomes attached to a host root, however, they will decline in vigor, remain stunted in growth, and never flower, or they will eventually die. The degree that a species can grow and develop without the host may vary widely between species.
Over the years, my fascination with this beautiful group of plants has led me to try growing, in containers, many different species from a wide variety of habitats. Here is my technique for growing Castilleja from seeds. [End Page 63]
Indian paintbrush is relatively easy to propagate from seeds. Seeds can be collected in midsummer for early spring flowering species and in late summer for mid-elevation species. High elevation species are collected during fall. In general, the dry dehiscent seed capsules ripen 8 to 10 w following pollinator activity. There are many tiny seeds per capsule. These are grayish to tan in color with a somewhat wrinkled or pitted surface.
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| Figure 1 |
Photo by Tara Luna
In a study, seeds of 8 western US Indian paintbrush species were essentially completely dormant without cold moist stratification (Meyer and Carlson 2004). Species and populations within species responded to cold moist stratification to at least some degree. In general, populations from warmer, low elevation sites had shorter chilling requirements and...