Friday, August 12, 2011

Succulents of Coastal Southern California: Dudleya

Dudleya pulverulenta on granitic rock in Vista, California, April 2011.

The San Diego area experiences some of the most agreeable weather in the world. It has a mild Mediterranean climate where frost is a rarity and unpleasant heat is almost as uncommon; for months on end the forecast is “morning fog in coastal areas, then sunny with a high near 80.” Given a little irrigation, a huge range of tropical and subtropical flowers and fruits will grow like mad. A breakfast of the most delicious oranges and avocados can be obtained by merely reaching up and plucking it from the trees. Southwestern California is a land of milk and honey.

All of this is common knowledge, and as a result there is hardly an acre of land in coastal Southern California that hasn’t been converted to houses, strip malls, roads and farms. But here and there, one can find remnants of the original scrubby chaparral vegetation, which includes some interesting succulent plants.

Plants from the genus Dudleya are the characteristic succulents of the coastal chaparral. Dudleyas are rosette plants with succulent leaves, which often resemble Echeveria. In some ways, Dudleya is the winter-rainfall climate equivalent of Echeveria (which are summer-growing plants), although the two genera are not closely related, with Dudleya falling out near Sedum in recent evolutionary studies of the family Crassulaceae.

Dudleya edulis (left) and D. pulverulenta (right) on the beach at Torrey Pines.

The most common Dudleya in the vicinity of San Diego is D. pulverulenta, the Chalk Rose, which favors rocky slopes and can occasionally be found growing in road cuts. Chalk Roses can be stunningly beautiful plants, waxy white and bigger than dinner plates, with tall racemes of red tubular flowers that are pollinated by hummingbirds.

Dudleya edulis, or Fingertips Live-forever, is a more strictly coastal species with upright cylindrical leaves, like handfuls of string beans. Supposedly, the leaves can be eaten as a raw or cooked vegetable. Another species that seems to be most frequent on the coast, though it can occur inland on mountains, is D. lanceolata, which looks a lot like a greenish, pointy-leaved Echeveria.

Dudleya lanceolata at Torrey Pines. The Martian weed around the Dudleya is Crassula connata, a tiny winter annual.

The rarest Dudleya of San Diego County is D. blochmaniae ssp. brevifolia, which is found on a handful of sites near the ocean, growing on patches of open ground among pebbly, iron-rich concretions. It is a tiny plant, with globular leaves only a centimeter or so long, which blend in well with the dark concretions. It only grows in the winter and spring, and dies back to a subterranean tuber in warm weather. Fortunately, the primary population of D. blochmaniae ssp. brevifolia is protected within Torrey Pines State Park.

Dudleya blochmaniae ssp. brevifolia, getting ready to flower in April at Torrey Pines.

Dudleyas hardly seem to be cultivated at all by C&S people on the eastern seaboard, possibly because they are strict winter-growers, which can be tricky to accommodate outside of Mediterranean climes. They don’t seem to be too difficult, though, if they can be given plenty of sun and a fair amount of water in the cooler months, and a warm, dry summer rest. Water can accumulate among the waxy leaves of species like D. pulverulenta, and this should be drained off in order to avoid rot. In the wild, the rosettes are often held near vertically against cliff faces, so pooling rain is not an issue.

I’ll have more on the cacti and succulents of Southern California in a future post.


Alex said...

Wonderful plants Dudleyas! When I lived out west I grew quite a few specimens. I miss them a bit.

Matt said...

Dudleya is a neat group-- I wish they were more available from commercial sources.

Julie said...

Southern California is my place to be. Love Torrey Pines...oh my I miss all that succulent beauty out there!!! Great shots of some gorgeous plants!