Cliff paintbrush -- Castilleja rupicola
Narrow crevices in alpine cliffs are surprising places to find plants. Despite their stark appearance, high alpine rock faces provide great habitat for all sorts of plants. But even when you know to expect them, seeing plants in such conditions is always impressive. I have marveled at boulder-splitting trees oozing from the crack in the rock from which they have eked out a living. Seeing fern species I associate with wet forests growing in boulder fields above the treeline has made clear to me the amazing adaptability of certain species. And of course this rocky landscape is home to so many colorful compact wildflowers that make high altitude hikes so much fun during the brief summer.
One of my favorite wildflowers of the Cascade Range rockeries is cliff paintbrush (Castilleja rupicola). The botanic species name rupicola, meaning rock dweller, is well suited for this plant. A serious amount of effort is sometimes required to get up to the land of the rock dwellers, but the reward is great. The intense red of these little plants contrast so well with the green mats of its cohabitants and the bleached rocks that they call home. Cliff paintbrush is one of the few wild plants I have seen vivid enough to almost hurt your eyes. Wild plants are often subtle beauties, but paintbrush species and cliff paintbrush in particular offer color to rival any garden cultivar.
The secret to success for cliff paintbrush and its fellow rock dwellers is found in the cracks. Deep crevices fill with weathered mineral-rich rock and accumulate organic matter over time. This provides just the right growing medium for these plants. The deep, shaded crevices are protected from the elements allowing them to retain water and sustain a more moderated temperature than the surrounding landscape. The plants that grow here, though often small above ground, tend to have very long roots that travel deep underground. So while viewed from the human perspective these plants can sometimes appear to be magically growing from rock, in truth all they need to do is reach deep enough into the rocky landscape to find the hospitable anchorage that many plants would enjoy.
Paintbrush species are hemiparasitic, meaning partial parasites. Individual plants produce some of their own energy through photosynthesis but reduce their workload by stealing food from other plants. They do this with specialized growth called haustoria that emerge from the roots and attaches to the roots of other plants. Paintbrush species are generally thought to grow more robustly when in close proximity to one of their hosts, specific species of wildflower and grasses. However, they are not obligate parasites and I have seen them growing in isolation enough to assume that while they must benefit from parasitic behavior, they are not incapable of sustaining themselves. Cliff paintbrush, isolated from other plants as it can be in small rock crevices, is a good example of a self-sufficient paintbrush.