Wholeleaf Paintbrush in the Landscape

Stephen Love, University of Idaho

Scientfic Name:  Castilleja integra
Common Name:  Wholeleaf Paintbrush, Wholeleaf Indian Paintbrush

Description:  Wholeleaf paintbrush is one of the universally recognized and adored wildflowers of the southwestern U.S. Uncommon in cultivated gardens, species in the Indian paintbrush genus are worthy of greater attention from the landscape industry. The key reason for minimal use in gardens is production barriers caused by the hemiparasitic (partially parasitic) nature of this genus. Appropriate host plants are essential for maintaining health and ultimately for survival of paintbrush growing in either pots or the garden. Wholeleaf paintbrush adapts more easily to cultivation than most other species from this genus, meaning that with the use of proper techniques, it can be cultivated and marketed as a horticultural product. Flowers of wholeleaf paintbrush are brilliant orange-red and bloom over a significant period of late spring and summer, typically from May into July. The intense color exhibited by wholeleaf paintbrush is dominating and the plants are best used to intentionally draw the eye to a specific part of the garden. Mature plants are about 12 to 15 inches tall and produce up to a dozen flowering stems. Plants are herbaceous, dying back to below the ground each fall and sprouting underground crowns each spring. Wholeleaf paintbrush can be used in xeric beds or borders. To satisfy the hemiparasitic nature of wholeleaf paintbrush, as well as maintain the aesthetic value of the garden, a plant species with good host traits and with complimentary size and color should be chosen as a propagation companion.

Native Habitat:  Castilleja integra is native to the high plains and foothills of Arizona, New Mexico, Colorado, and Texas. Often found within a wide range of plant communities, including woodlands, mesas, grassy plains, dry prairies, and slopes; typically on gravelly or rocky soil. This species commonly grows at elevations ranging from 3,000 to 8,500 feet.

Cultural Requirement

Soil:  Adapted to a range of soil types and conditions, including alkaline soils, but requires well-drained conditions. Requires minimal soil fertility.

Moisture Tolerance:  Adapted to relatively dry conditions and requires some supplemental irrigation only in locations where summer moisture is infrequent. Moisture management decisions should also account for the needs of the host species.

Sun/Shade/Preference:  Prefers full sun.

Transplanting:  Wholeleaf paintbrush can be seeded in flats and germinated in the absence of a host species. Soon thereafter, plants must be paired in pots with an appropriate host species. Plants grow at a fast pace after transplanting and can easily be brought to bloom in pots. Survival after transplanting to the garden is dependent on presence of a host whose roots form a solid root ball.

Propagation:  Best grown from seeds. Difficult or impossible to propagate from cuttings. Seeds emerge more uniformly and quickly following an 8-week stratification period. Young seedlings grow comparatively rapidly. When the plants are 2 to 4 inches tall, the seedlings must transplanted into a pot along with a suitable host plant to continue growing and develop sufficiently to survive transplanting. Good host species include gray rabbitbrush (Ericameria nauseosa), fringed sage (Artemisia frigida), Michaux’s sage (Artemisia michauxiana), pineleaf penstemon (Penstemon pinifolius), Cusick’s hyssop (Agastache cusickii), and Jame’s buckwheat (Eriogonum jamesii). Wholeleaf paintbrush plants are best grown in 4-inch

Maintenance (pruning, fertilization, deadheading, division, irrigation, etc):  Wholeleaf paintbrush is an easy-care species. In early fall, senescing stems will need to be removed to maintain appearance. Supplemental irrigation is required in the driest of regions. Fertilizer is required only if paintbrush or host plants show poor vigor.

Insect, disease, or other problems:  Wholeleaf paintbrush typically exhibits minimal problems with pests or diseases. Aphids may infest the plants just prior to bloom, but usually disappear within a week or two without application of insecticides.

Landscape Value

Use in the Landscape:  Wholeleaf paintbrush is valuable for its ability to provide spectacular color in the landscape. This species can be grouped to beautify a particular part of a garden. It can be used as a repetitive feature to create visual lines. Paintbrush plants create garden habitat for native pollinators. If paired with an appropriate host, wholeleaf paintbrush will contribute to season-long aesthetic value in a moderately xeric site.

Weediness/Invasive Potential:  Although occasional seedlings will show up in the garden, wholeleaf paintbrush is not considered weedy from seed nor does it spread from rhizomes.

Foliage:  Stems of wholeleaf paintbrush grow from an underground crown. Stems are primarily unbranched from the base, although some stems may branch one or more times close to the ground. Leaves form on the flowering stems, lack lobes and are narrow and lance-shaped. Foliage is mostly hairless. The foliage is fairly attractive, but not showy.

Flower:  The bright color of wholeleaf paintbrush is the result of showy bracts that surround the green flowers. Numerous flowers open sequentially from the bottom to the top of 5 to 8 inch heads. Flower bracts are intensely red to orange-red.

Timing:  May-July.

Fruit:  Each flower produces a dry capsule that holds numerous uniquely textured tan seeds.

Form:  Upright to slightly spreading spike-like flower stems.

Texture:  Moderately coarse.

Ultimate Size:  In bloom, mature plants are 12 to 15 inches tall and have a 10 inch spread.

Rate of Growth:  Wholeleaf paintbrush grows at a rapid rate and can easily be brought to bloom in pots before transplanting or during the first-season in the garden.

Suggested Plant Partners:  Two separate considerations are required when deciding what to place in the landscape with wholeleaf paintbrush. The first is choice of host species, with suggestions given above in the propagation section. The second is complementation in the garden. Because wholeleaf paintbrush is a relatively short plant, the best options for companions include short-statured species such as: desert zinnia (Zinnia grandiflora), rosy pussytoes (Antennaria rosea), rock columbine (Aquilegia scopulorum), suncups (Calylophus serrulatus), Douglas’ buckwheat (Eriogonum douglasii), roundleaf alumroot (Heuchera cylindrica), tufted evening primrose (Oenothera caespitosa), Hall’s penstemon (Penstemon hallii), Idaho fescue (Festuca idahoensis), and blue gramma (Bouteloua gracilis).

Availability:  Potted plants are rarely available for purchase. Seed can be purchased from native plant seed suppliers.

Cultivars:  No cultivars available.

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