Paintbrushes dot grassy landscapes along the Colorado Plateau, emerging with seasonal rains. The flame-colored plant is a common sight, with over 220 distinct species. Castilleja, the genus containing paintbrushes, can be found growing in clumps from grassy steppes to alpine tundras. This blazing red wildflower, though striking, was once deemed “Colorado’s vampire plant” by the Denver Botanic Gardens because of its deeply buried secret.
Most plants create their own “food” by using sunlight, water, and carbon dioxide to produce sugars through photosynthesis.
Paintbrushes, on the other hand, are partial parasites. They photosynthesize and produce some of their own energy, but they rely heavily on nearby host plants to supply most of their nutrition.
To access these resources, paintbrushes pierce the roots of nearby plants, leaching carbohydrates and other nutrients from their neighbors.
Paintbrushes can even absorb chemical compounds from their host plants and incorporate them into their own tissues. When growing alongside legumes like lupines, paintbrushes tend to produce more seeds than when growing with grasses. The plants that paintbrushes parasitize can influence their growth, seed production, and the color of their distinctive feathery bracts. Those “petals” aren’t petals at all, but uniquely modified leaves surrounding small, green flowers.
Parasitic plants like paintbrushes may actually benefit plant communities by increasing species diversity, drawing resources from dominant species and allowing weaker competitors to coexist. They’re just one example of a strange, intricate, and often invisible ecological dance.
This Earth Note was written by Danika Thiele and produced by KNAU and the Sustainable Communities Program at Northern Arizona University.
