Swale paintbrush has been recorded in mesic sites (areas with moderate moisture) such as seasonally wet grasslands and savannahs at high-elevation basins and valleys above 4,000 feet (1,500 meters). Additionally, the plant has been found at elevations ranging from approximately 4,920 to 7,550 feet (1,500 to 2,300 meters).

Throughout its range, precipitation follows a bimodal pattern, with approximately two-thirds of annual precipitation occurring during the summer monsoon period (June to August) and the remainder occurring primarily in the winter. During the summer (May through September), known occupied areas receive about 9 to 18 inches (24 to 45 centimeters) of precipitation.

Stressors on its habitat include habitat loss and fragmentation, hydrological alteration, altered fire regimes, the effects of intensive grazing pressure, exotic plant invasion and climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.

Learn more about climate change . 

Swale paintbrush is an herbaceous annual that starts as a basal rosette, or a circle of leaves at ground level. Mature plants have a single or small number of erect or ascending stems with clasping leaves and bracts. The stems often branch from near the base of the plant. Both the leaves and bracts (modified leaves) are distinctively wavy-margined.

Swale paintbrush grows to about 6.5 to 14 inches (17 to 35 centimeters) tall and has a thin taproot or fibrous root system that is relatively shallow, typically only a few inches long documented in specimen records. Leaves range in size from 0.8 to 1.6 inches (2 to 4 centimeters) in length. 

Swale paintbrush has green to purple-tinged leaves, and its bracts look like flowers. Its floral bract tips have an unusual color, typically pale to greenish-white, and fade to a beautiful rosy to purple color as they age. Some plants have yellow, orange or red bracts. The plant’s actual flowers are inconspicuous, hidden within its showy bracts. The outermost part of the flower (calyx) contains cuts (clefts). The calyx is green and may have a white edge that turns pink as it ages. 

Plants sprout from late May to early June, although some may germinate as late as June. The peak flowering period occurs in mid to late August. While the phenology (timing and pattern of biological events) of swale paintbrush seems to occur with monsoon season precipitation, direct correlations between its population abundance and monsoon season precipitation amounts are elusive. Since juvenile swale paintbrush have not been observed in early spring, it is hypothesized that nondormant seeds need high temperatures and sufficient moisture to trigger germination after overcoming dormancy.

Although swale paintbrush photosynthesizes, it needs carbon, nitrogen and other nutrients from the roots of host plants to achieve optimum growth and reproductive potential. Native grasses, including alkali sacaton (Sporobolus airoides) and blue grama (Bouteloua gracilis), are thought to be the primary host plants within the Animas Valley population. Young swale paintbrush plants establish connections with host plant roots via structures called haustoria.

Swale paintbrush is an annual plant that survives for one growing season. The longevity of its seeds is unknown. Surrogate Castilleja species have seed longevity of up to five years in storage and up to two years in the wild. Because of this, the plant requires frequent resupply of the seed bank for a population to continue. 

The plant likely cannot self-fertilize because its stigma is physically separated from its anthers, and wind pollination is unlikely because stamens are protected from wind by floral tubes. Healthy populations of local native pollinators support successful reproduction of swale paintbrush. The pollinators of swale paintbrush are unknown, and potential pollinators include bumblebees (Bombus spp.), sweat bees (family Halictidae), hummingbirds (family Trochilidae), and thrips (order Thysanoptera). Hummingbirds primarily pollinate Castilleja species with red floral bracts, while insects are presumed to be the primary pollinators for Castilleja species with yellow floral bracts. 

Most seeds are likely shaken from seed capsules by wind and settle to the ground within a short distance of the parent plant. However, these seeds are lightweight and surrounded by an aerodynamic, honeycombed shell that could be carried further by wind. Additionally, insects and small mammals likely contribute to local seed dispersal. While rare, long-distance dispersal events are possible, natural colonization of new sites primarily occurs through a series of short dispersals over time.

Because of its distinctive wavy-margined leaves and off-white bracts, Swale paintbrushis unlikely to be confused with any other Castilleja species in New Mexico. The co-occurring annual Castilleja species within New Mexico (thread-torch paintbrush (C. minor)and purple owl’s-clover (C. exserta) are easily distinguished by their bright red or pink to magenta floral bract tips, respectively. However, within Mexico, several Castilleja species have been misidentified as swale paintbrush and these include C. sphaerostigma (no common name), C. glandulosa (no common name), rigid paintbrush (C. rigida), and C. stenophylla (no common name).