Stone-crop Family (Crassulaceae)
Plant Type: Succulents.
Geographic Zones: Varies with species.
Light: Sun to partial shade.
Soil: Varies with species.
Water: Drought tolerant to infrequent; usually essential to avoid summer watering.
Natural Habitat and Range: Rocky, clayey, or sandy sites in coastal scrub, chaparral, mixed-evergreen forests, and deserts to 9000 feet; California Floristic Province, with a few species in Arizona, Oregon, and the Cape Province of Baja California.
One of the common names for Dudleya is “liveforever,” which speaks volumes about this western North American genus that thrives on neglect. Some species reputedly live as long as fifty to one hundred years, others a “mere” twenty. This genus contains a number of California’s most rewarding succulents for use in horticulture. Its numerous species offer a dizzying array of leaf shapes, sizes, habits, and flower colors for the garden.
Garden forms of dudleyas come in two distinct types: branching and unbranching. Both types are ideal for succulent and rock gardens. Branching species develop multiple rosettes that form low, tufted colonies, while unbranched species produce a solitary rosette. The colony formers are valuable groundcovers in the front of a border, whereas the single rosettes make excellent container specimens and focal points in beds.
Most of the myriad habitats dudleyas occupy become dry in summer. Therefore, it is important to cut off water to dudleyas in your garden during summer. Plants grown in sandy soils or containers are exceptions; they will accept infrequent summer watering as long as the soil drains well. The onset of fall or winter rains reawakens dudleyas from drought-induced dormancy. Their shriveled leaves plump up quickly, growth resumes, and flowering occurs during the next spring or summer. Dudleyas are amazingly resilient; if a portion of a colony sloughs off a cliff face or is uprooted by a burrowing animal, it can persist for months until soil contact is reestablished. Species that naturally grow on ocean bluffs are also salt-spray tolerant.
Dudleyas have their share of disease and pest problems. If you can prevent Argentine ants from introducing mealybugs or aphids to your dudleyas, they will be healthier. Mealybugs nestle in the deep recesses of the leaves, and their feeding weakens the plants. They may also be vectors, along with aphids, for a virus that disfigures the foliage. Aphids commonly attack emerging flower stalks, and should be washed off carefully with soapy water or a strong jet of water.
Snails and slugs relish the juicy foliage of dudleyas and leave telltale holes. Avoid overwatering, which attracts these creatures and also favors root-rotting, soil-borne pathogens that may kill the plants. Provide ample air circulation to minimize fungal disease organisms, such as powdery mildew and Alternaria. Powdery mildew invades leaf tissues and causes browning and scarring of the upper surface; Alternaria produces ugly brownish black spots. Dudleyas are particularly susceptible to rot above ground if moisture accumulates in the rosette; plant them on a slight angle to drain water away more quickly. Browsing by rabbits and deer can reduce dudleya rosettes to nubs; to ensure your dudleyas have a chance to grow, you will need to exclude these animals from your garden.
Only a handful of the roughly forty species of dudleya are reliably available. Several species are quite rare in the wild and are now protected by law. Thankfully, a number of nurseries and botanic gardens continue to responsibly propagate many choice species. For greatest success in cultivation, choose species from your local area.
Britton dudleya (Dudleya brittonii) is prized for its strikingly beautiful 6- to 12-inch-wide solitary rosette. The whitish coating (rarely green) on the flattened 1- to 2-inch-wide leaves accounts for its luminous appearance. In spring, the flower stalk, which measures 11⁄2 to 21⁄2 feet, elongates and turns dark red as the pale yellow flowers open. This native of northwestern Baja California occurs primarily on steep bluffs in maritime coastal scrub. Possibly the most popular dudleya in cultivation, Britton dudleya makes a perfect accent in beds or containers. Plant it in well-drained soil, provide full sun near the coast or some shade inland, and protect it from freezing temperatures.
Candleholder dudleya (D. candelabrum), one of many island-endemic dudleyas, is restricted to Santa Cruz, Santa Rosa, and San Miguel islands. Found on rocky ridges and slopes, its solitary rosettes average 6 to 10 inches across. The flattened 3- to 6-inch-long and 1- to 21⁄2-inch-wide green leaves have a chunky look. The species gets its common name from its candelabra- like inflorescences, which bear numerous pale yellow flowers in tight clusters. It is somewhat frost tolerant.
Canyon dudleya (D. cymosa) is a highly variable, diminutive dudleya esteemed for its colorful floral display. The flowers range from pale to bright yellow to orange or red. The wide, flattened leaves are also variable in color and the caudex may be branched or simple. Canyon dudleya occurs in rocky outcrops on slopes throughout the California Floristic Province, except the Central Valley. Try growing this challenging species in containers, and keep it dry during its summer dormancy.
Chalk dudleya (D. pulverulenta) is spectacular in bloom. It has foliage similar to Britton dudleya, and its red flowers contrast handsomely with the white stalks. This widespread species occurs in coastal scrub and chaparral plant communities from San Luis Obispo County south to Baja California. It typically grows on slopes and appears to defy gravity by adorning steep cliff faces. Try several nestled in the crevices of a rock wall for a dramatic look. Chalk dudleya is more frost tolerant than Britton dudleya. Plant it in part shade, and leave it completely dry in summer.
Catalina Island dudleya (D. virens subsp. hassei) is endemic to Santa Catalina Island. The densely clustered rosettes of grayish white leaves are 3 to 6 inches across. This profusely branching species is the best groundcover dudleya and is also valued for its tolerance of heavy soils.
Cultivar: ‘Frank Reinelt’ (= ‘Anacapa’) forms tight, low mounds about 6 to 8 inches tall and 12 or more inches wide. It has very silvery leaves, which flush to rose-purple in winter.
Excerpted and adapted, with permission, from California Native Plants for the Garden, published in 2005 by Cachuma Press and now available in book stores and nurseries, or online at www.cachumapress.com.