Dudleya Pulverulenta

''Dudleya pulverulenta'' is a species of perennial succulent plant known by the common names chalk lettuce, chalk dudleya, and chalk liveforever. It is one of the largest ''Dudleya'', with a silvery, waxy rosette that may greatly contrast with its habitat. It is also regarded as one of the most distinctive members of the ''Dudleya'', with the most advanced inflorescence in the genus, consisting of pendant, hummingbird pollinated flowers, the longest corolla, and the highest nectar output, along with the largest range of all the ''Dudleya'', over , being found from southern Monterey County in California to the Sierra de San Borja in southern Baja California.

Description

''Dudleya pulverulenta'' is a rosette-forming, succulent species of plant, covered in a distinctive chalky and mealy wax, known as a farina, or more technically, epicuticular wax. It is one of the largest species of ''Dudleya''. All parts of the inflorescence are covered in a chalky wax, and the flowering stems may reach up to long. The long, red flowers hang downward, an adaptation to hummingbird pollinators. After flowering, the fruits are turned erect by a sharp turn of the branchlet, known as a pedicel, connecting the flower to the inflorescence. This unique syndrome is only shared by '' Dudleya anthonyi'', a close relative, and '' Dudleya rigida'', an extremely rare species found in far southern Baja California Sur. '' Dudleya arizonica'' is similar in appearance, and approaches ''D. pulverulenta'' in many aspects, but lacks the downward-pointing flowers and unique fruiting behavior, instead having erect flowers and a more reduced size.

Morphology

''Dudleya pulverulenta'' grows a thick caudex, wide. As the plant grows older, the stem gradually becomes decumbent. The stem is densely clothed with old, dried leaves. Atop this stem is a solitary rosette, as the stems do not form axillary branches. The rosette reaches a width of , and is composed of 40 to 60 wide, flat, fleshy, chalky white leaves which age to a pinkish papery texture. The leaves are shaped oblong, broadest at the base or upper third, with the tip acuminate to mucronate, or acute. The leaves are long by wide, and are thick. The epidermis of the plant is covered with a dense coating of chalky, powdery epicuticular wax.

The peduncle is tall by wide, and is covered in 20 to 70 bracts. The bracts are spreading to deflexed, and are shaped cordate-ovate to suborbiculate, with an acuminate tip. The bracts measure long by wide, and may be a reddish color. The peduncle branches into 2 to 6 branches, which may or may not rebranch. There are 2 to 5 terminal branches, known as cincinni, that are nodding in youth but become spreading in age, and measure long. The cincinni are circinate, unfurling like the frond of a fern. The cincinni hold 10 to 30 flowers, and are twisted at the base, so that the flowers are on the underside.

Suspending the flowers pendant are the pedicels, which measure long. In age, the pedicels sharply bend in the near middle to bring the fruits to a more or less erect position. The calyx measures long by wide, with mostly acute sepals. The petals are long, and united for along their length. The apex of the petals is shaped acute to obtuse, with the tips erect. The sepals are waxy, while the petals are red, with some wax.

''Dudleya pulverulenta'' flowers in early summer, usually from May to July. Plants subject to full sun close their rosettes during the summer, and in July to August the leaves will begin to fold upward and inward, "shrinking" in the heightened temperatures. Plants on north-facing or shaded slopes are less likely to close their rosettes.

Phytochemistry

Higher temperatures are tolerated well by ''Dudleya'' because of their epicuticular wax, which reflects light and prevents evaporation of water droplets.

Taxonomy

The type specimen was collected by Thomas Nutall in San Diego, in May 1835. ''Dudleya puvlerulenta'' hybridizes with ''Dudleya lanceolata'' where they overlap in their ranges.

Characteristics

''Dudleya pulverulenta'' intergrades with both ''Dudleya anthonyi'' and ''Dudleya arizonica'', and the boundaries between these three entities are not always clearly defined. ''Dudleya brittonii'' bears a superficial resemblance to this species, but differs significantly in its smaller yellowish-white flowers and dense inflorescence. Two charts (below) compares the characteristics of these four species.

Distribution and habitat

''Dudleya pulverulenta'' is native to California and Baja California. Its range extends from extreme southern Monterey County southward to Punta Prieta in the central desert of Baja California. It is typically found in rocky cliffs, and canyons, generally under 1000 meters in elevation. It is primarily a plant of coastal distribution and can often be found within 12 miles of the coast, and more inland occurrences are typically in valleys where the heat is moderated by elevation or coastal influence.

Plants are very rapid recolonizers as evidenced by proliferation on roadcuts or disturbed soil shortly after development. Their habitat preference for rocky, shallow soils and open habitats mean that fuel is limited in proximity to the plants, enabling them to survive wildfire. The plant will resprout after fire.

Cultivation

The plant tolerates full sun exposure or part shade. It is susceptible to aphid infestations which result in flower and rosette deformities. It is a much hardier plant for the garden environment than the more commonly available ''Dudleya brittonii''.

''Dudleya pulverulenta'' is not noted for its longevity and may only live up to 2 or 3 years in cultivation, but some specimens in the wild may be over 40 years old in a most optimal location. When the plant dies, the rosette takes on a withered, ashy gray appearance, resembling a bird's nest. It is important to note whether the center leaves of the rosette are still alive, as the dormant plant will often surround a few live leaves with a ring of withered leaves until the next growing season pushes them down.

See also

* '' Dudleya anthonyi''
* '' Dudleya arizonica''
* ''Dudleya brittonii''

References

External links

Jepson Manual Treatment of ''Dudleya pulverulenta''USDA Plants Profile for ''Dudleya pulverulenta''U.C. Photos gallery − ''Dudleya pulverulenta''

{{Taxonbar, from=Q5226268

Dudleya, pulverulenta
Flora of California
Flora of Baja California
Natural history of the California chaparral and woodlands
Natural history of the Peninsular Ranges
Natural history of the Santa Monica Mountains
Natural history of the Transverse Ranges
Garden plants of North America
Drought-tolerant plants
Taxa named by Thomas Nuttall
Taxa named by Joseph Nelson Rose
Taxa named by Nathaniel Lord Britton