Coastal Dudleya


Succulentopedia

Dudleya caespitosa (Coast Dudleya)

Dudleya caespitosa (Coast Dudleya) is a succulent that forms rosettes of fleshy, green or greyish-green, usually oblong to oblanceolate…


Tom Karwin, On Gardening | California succulent Dudleyas

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Local gardeners recently attended an absorbing presentation about a highly regarded native California succulent plant, the Dudleya. Stephen McCabe, emeritus director of Research for the UC Santa Cruz Arboretum spoke to members of the Monterey Bay Area Cactus & Succulent Society (MBACSS) on “Dudleya Poaching, Conservation and Cultivation.”

Steve McCabe photographs cliff-dwelling Dudleya densiflora. (Contributed — Steve McCabe)

The Genus Dudleya

Dudleyas are native to California and other western American states, and in the case some species, to Mexico. The genus includes 40 to 50 species, a small number compared to several other garden plant genera. Plant hunters like McCabe occasionally discover additional species in remote areas.

We think of Dudleyas growing on cliffs along the Pacific coast. While such areas provide excellent growing conditions for many Dudleyas, some species also grow well in diverse environments, generally west of the Rocky Mountains.

Dudleyas are called “Liveforever” plants, in recognition of their potential for thriving for up to a century, given supportive growing conditions.

Dudleya cymosa (Canyon Liveforever) growing in nature. (Contributed — Steve McCabe)

Poaching

McCabe described how individuals have poached Dudleyas from their natural environments, intending to ship the plants to collectors in China, Korea and other Asian countries. Evidently, there is a strong market for improperly collected Dudleyas, particularly the less common species. These plants are popular because their limited availability through commercial channels, combined with their compact size, attractive appearance and ease of outdoor cultivation.

Poaching of Dudleyas has been reported since early 2017. A series of arrests revealed that thieves were taking up to thousands of plants at a time, vandalizing natural populations of the plants.

The California Department of Fish & Game has initiated a range of enforcement strategies in continuing efforts to frustrate poachers who look for plants in relatively remote sites, and confiscate their plants. A high-tech strategy under development will identify wild Dudleya plants by testing for commercial fertilizers, which would be present only in nursery-grown plants.

McCabe works with the Department of Fish & Game, the California Native Plant Society and the Arboretum to return confiscated plants to their native settings, when feasible. In addition, he and other conservationists are propagating and distributing selected species with the long-term goal of satisfying gardeners’ demands for nursery-grown plants and reducing the desire to uproot wild Dudleyas.

McCabe is also hybridizing Dudleyas to create “pretty plants” that would be particularly desirable to both serious collectors and casual gardeners. Examples of such specimens include white-leaved and relatively uncommon red-leaved Dudleyas. His hybrids will be available in the near future at Norrie’s Gift & Garden Shop in the UCSC Arboretum.

Dudleya hybrid ‘Edna’s Echidna’ resembling a spiny anteater. (Contributed — Steve McCabe)

During his talk for the MBACSS, McCabe distributed nursery-grown Dudleyas and packets of seeds for participants who are prepared for seed-propagation.

Cultivation

McCabe advised on best practices for growing Dudleyas in the garden, emphasizing that coastal Dudleya species welcome the ocean’s salty sprays, constant winds, and the heat and ultraviolet rays of the sun. They are acclimated to mildly cold winter seasons and dry summers. He recommended providing Dudleyas with full exposure to the sun, fast-draining soil, and minimal irrigation during the summer months. A good practice is to plant Dudleyas tilted to one side, matching their natural growth position on cliffsides.

McCabe noted that Dudleyas are accustomed to demanding outdoor conditions and are not well-suited for indoor cultivation.

Dudleya leaves often have a whitish surface due to a layer of wax known as farina, which protects the plant from an excess of sunlight. Gardeners who grow Dudleyas are careful to avoid touching this waxy layer because doing so leaves a permanent blemish on the leaf.

Dudleya ceaspitosa ‘Lucia Form’ found in Lucia, California. (Contributed — Steve McCabe)

Steve McCabe will speak again at the UCSC Arboretum at 7 p.m. Feb. 12. For information, visit arboretum.ucsc.edu and click on “News & Events.”

Interested gardeners could help to conserve this California native plant by growing nursery-grown Dudleyas in their gardens. Several species are strikingly attractive, and the new wave of hybrid “pretty plants” will be particularly desirable.


Dudleyas: Plant Care and Collection of Varieties

These rosette succulents are mostly native to California and Baja California, though their range also extends into Oregon and Arizona. Most species are found along the coast or on offshore islands, where they experience regular fog, high humidity, winter rainfall, and summer drought. The few whose range extends inland tolerate greater temperature extremes.

They vary in size from miniature (the Hasseanthus group, with no above ground stem) to medium size (D. brittonii, which can grow to a couple of feet wide). The leaves may or may not have a white powdery dusting. Flowers, which are useful for identification, may be open (flat), closed (tubular) or intermediate, and they attract bees and hummingbirds. Most Dudleyas flower in great abundance once a year when they are thriving.

Care
In mild coastal climates, Dudleyas enjoy plenty of exposure, up to day-long sun, especially the powder-dusted species. They are generally salt-tolerant and well-suited for oceanside gardens. Where summer heat is an issue, they will require some protection, but strong light is important for health and proper form. Dudleyas prefer excellent drainage and enjoy regular water during their period of active growth (fall through spring). But do not mistake summer dormancy for thirst -- it is quite the opposite. + Show More

Dudleyas are excellent container plants and will grow to quite different sizes depending on the size of the container, being dwarfed in small containers and exuberant in larger ones. In mild areas they are very practical landscape plants which require little or no summer irrigation. They are ideally suited to Mediterranean (dry-summer) climates. They do not do well where there is much summer rain, so provide overhead protection at that time of year if necessary. Dudleyas are not recommended as indoor plants unless you can provide hours of sun each day during the winter months.

When potting up Dudleyas, especially the ones that clump, it is important to use top dressing, so the dead leaves do not come in contact with wet soil.

Container Dudleyas require vigilance for the presence of insect pests. Immature inflorescences often attract aphids. The farinaceous species are particularly vulnerable to attack by mealy bugs, because the bugs are camouflaged against the white background. Insect damage to the core may be so severe that the growth point disappears, but much of the time the plant will respond by branching. Distorted leaves may be a warning sign of insect activity in the core.

Identification
Three factors are important in arriving at an accurate identification of Dudleya species. (1) Knowing the geographical origin of a plant will help reduce the number of options to choose from. (2) Seeing the flower will allow you to place the plant within a subgenus (based on shape), and in some cases tell you the species (based on color). Some flowers also have an informative odor. (3) Observing the rosette itself, to see whether stems branch, what color and shape the leaves are, and if they die off in the summer, will also help narrow the options. + Show More

The 50 or so species of Dudleya can be divided into three subgenera: Hasseanthus (a small group of plants with no above-ground stem), Stylophyllum (plants with open flowers), and Dudleya (plants with tubular or cup-shaped flowers). The greatest number of species are in the latter subgenus. Interestingly, the final 2 subgenera are not actually distinct groups based on DNA studies.

Hasseanthus is quite rare in cultivation. It can be distinguished by a below-ground stem and Sedum-like flowers that open wide at the base. Stylophyllum flowers are also open but midway up the flower, above the calyx. Subgenus Dudleya flowers are closed and roughly tubular but may be spreading at the mouth.

Identification of Dudleyas is complicated by natural variation and the presence of both natural and artificial hybrids. The large, powder-dusted rosettes of D. brittonii, pulverenta, and anthonyi may be tricky to resolve without seeing the flowers. The coastal species D. ingens and the green form of D. brittonii are also tricky to resolve, unless you know the origin.

Propagation
Dudleya seeds are small, almost dust-like, but seedlings can be quick (1-2 years) to grow full sized rosettes. Hybrids are occasionally seen where two species bloom together. The species which branch can be easily propagated from cuttings in the fall or winter. The species which do not branch can be forced by coring.

No Dudleyas outside the Hasseanthus group can be propagated from leaves. That group is said to bloom at 5 months of age with good greenhouse care, and lose its living leaves in the spring. The other plants in the genus may bloom within their first year from seed, provided nursery care.

Relatives
Dudleya is related to other New World Crassulaceae including Echeveria, which is separate geographically (found on mainland Mexico and parts south, not on the peninsula of Baja California). It may be difficult to distinguish the two genera without floral features. Echeveria flowers are always tubular, while Dudleya flowers may be tubular, flat, or cup-shaped.


California Native Plants for the Garden: Dudleyas

Carol Bornstein is one of Southern California’s most highly respected native plant specialists and co-author with David Fross and Bart O’Brien…

David Fross is one of Southern California’s most highly respected native plant specialists and co-author with Bart O’Brien and Carol Bornstein…

Chalk dudleya (Dudleya pulverulenta) tucked between rocks bordering steps in a private garden in Montecito. Photograph by Stephen Ingram

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.

Britton dudleya (Dudleya brittonii) in a decorative pot in a Sebastopol garden. Photograph by Phil Van Soelen

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 (Dudleya virens subsp. hassei) in a rock garden at the Leaning Pine Arboretum, San Luis Obispo. Photograph by David Fross

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.

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