Castilleja integra: Mascot of the 2023 Spring Plant Sale

May 1, 2023 Michael Guidi , Manager of Horticulture Research

Spring Plant Sale at Denver Botanic Gardens is a great place to find interesting and unusual plants that are difficult to source at garden centers and retail nurseries. Sometimes we have plants that you didn’t even know were possible to grow. You probably noticed the stunning advertisements for the 2023 Spring Plant Sale feature a beautiful, red wildflower that you might recognize from Colorado’s high plains and foothills. This plant is Castilleja integra, known by the common name whole-leaf paintbrush, and is one of the most noticeable wildflowers in Colorado. The showy red bracts stand out in almost any landscape and contrast beautifully against the tawny hues of grasses or silver foliage of shrubs that they grow alongside. 
Unlike most plants, Castilleja are hemi-parasites, meaning that they need a host plant to grow well. As you might imagine, this makes them difficult to grow, but the Gardens is conducting research to evaluate which host plants and methods of pairing lead to the greatest survival in cultivation. This work means that you can find Castilleja for sale in the Grown at the Gardens division at the sale May 12 and 13. 

When you purchase Castilleja from the Gardens, you’ll receive two plants (what a deal!), because the Castilleja are planted with a host plant in the same pot. When it’s time to plant, keep both plants together, taking care to minimize disturbance to the roots and plant into a well-draining soil, ideally with an inorganic mulch like pea gravel. Water-in the plants well and apply water regularly over the next 4-6 weeks just as the top inch of soil is drying out. Castilleja integra and its host plant will require very little water once they are established and are suitable for a xeriscape or low-water landscape. 

Learn more about the ecology of these unusual plants and research that is improving our ability to grow them in our gardens.

See you at Spring Plant Sale! Admission to the sale is free but reservations are required. Learn more and get reservations.


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