Sunday, January 02, 2011

Aeonium Arboreum

What’s happening: A thin layer of snow still covers many things; it’ll be a few days before the effects of the dry cold become obvious.

What’s still green: Juniper and other evergreens, Apache plume, yuccas, Japanese honeysuckle, pyracantha leaves.

What’s grey, blue-grey or grey-green: Piñon, four-winged salt bush, pinks, snow-in-summer, winterfat, golden hairy aster leaves.

What’s red/turning red: Cholla, prickly pear.

What’s yellow/turning yellow: Arborvitae; globe and weeping willow branches.

What’s blooming inside: Christmas cactus, aptenia, asparagus fern.

Animal sightings: Tracks of rabbit and something small with five toes in the snow.

Weather: Snow Thursday, followed by morning temperatures close to zero, the coldest I remember here; 9:50 hours of daylight today.

Weekly update: Seed catalogs have been arriving since Thanksgiving with their promises of a Hicksian peaceable kingdom where ferns and yuccas can co-exist in the same bed.

In Wildseed’s catalog, tuber vervain, which only inhabits the south from California to Virginia, is followed by wallflowers, which live only to the north. It implies one doesn’t need to live in the narrow band of counties in Kentucky and Virginia where the two species are native to enjoy both.

For those of us who have no luck with seeds, Stokes tells nurserymen how to sow pansies and impatiens so they’ll be in the stores when we want them. They don’t promise the native of cool springs in Europe and the rain forest child of New Guinea will grow in the same environmentally controlled room, but they can be produced by the same operation and planted in the same garden.

The international bazaar isn’t just the chimera of some bright copywriter. Here in highland New Mexico in frigid January, where some plants find cold moisture and afternoons above freezing stimulating, I don’t have to settle for the moss by the garage or the western stickseed by the fence post. I can look at new growth on the snow-in-summer from the Italian Apennines and the snapdragons from northeastern Spain. If I prefer to stay in my warm enclosed porch, I can look north to the Christmas cactus from Brazil or south at new leaves on the aeonium from the Spanish Canary Islands.

If Spain and Portugal appear more often than other countries in this list of homes for the tamed exotics, it’s only because their great explorations created a new vision of the possible. The Canaries, with their relict laurel forests from the time before the Mediterranean climate developed, lay in the path of the trade winds that carried European ships to and from the new worlds.

The seven islands reside on the thin ocean crust of the African plate, just west of Morocco, which rests firmly on the continental crust. As the plate shifted north in the early Miocene, volcanoes erupted on the periphery some 21 million years ago to form the first of the islands, Fuerteventura. Other the next millenia, the plates continued to drift and volcanoes and islands continued to form farther and farther west.

Around 15 million years ago, the first ancestor of aeoniums arrived on Fuerteventura, some member of the Crassula family that had migrated north along the eastern Africa coast, then west. As the islands formed, the newly created aeonium continued to migrate, adapting to each environment, until some 36 species have evolved in the Canaries, most unique to specific islands.

Eventually the plates moved so much they shut the Mediterranean sea from the Atlantic, precipitating a period of heat and dessication about 5.9 million years ago. A few million years later, some aeonium, probably some precursor of Aeonium balsamiferum, migrated from Lanzarote or Fuertaventura to an area of limestone rocks between Ida-ou-Tanane and the mouth of oued Noun on the Moroccan coast. With time that became the Aeonium arboreum growing on my porch.

How one species managed to jump what today is at least a 70 mile gap is open to speculation. One group noticed that while arboreum has none of the morphological features that attract birds, it’s the only aeonium that attracts nectar feeding species. Debra Lee Baldwin discovered, quite accidentally, that if she left cut stems of arboreum in water, they developed roots.

How I got my aeonium is simply another episode in the globalization of our choices that began with the great navigators. No matter how rationalized the empire or trade network, there are always colonial outposts where unwanted surpluses can be dumped. I’m no longer surprised by the oddities that wash up in the local hardware store, only a bit cautious about buying the unfamiliar.

Two years ago, strange succulents were being sold off in June. Gerald Klingaman thinks arboreums were being promoted as unusual Father’s Day gifts in Arkansas that year. I wondered fleetingly if they were intended for deck pots, but figured whatever they were, they might grow in my indoor porch. I bought two.

Perceptions of the exotic change with familiarity. When Philip Barker Webb first described the green leaved rosettes that grew on woody stems in 1840, any succulent was considered a novelty. When varieties that had adapted to the intense summer sun with dark burgundy leaves were made available in the early 1980's, they were eagerly grown by desert gardeners in California.

When I grew up, there were hens and chickens in the yard, along with purple leafed barberry. I found nothing unusual about a purple succulent sold to grow in an ordinary garden. What I’ve found odd is another of its environmental adaptations, it grows in winter and rests in summer.

For the first two years the two plants did little more than provide a color contrast with the surrounding aptenia. Last January they must have put out new leaves, bright light green until they matured. For some reason, I took their picture.

Then, for the first time, these coddled plants of civilization faced the crises of their feral ancestors. I forgot to water them in February. They wilted. The porch heater got too ambitious in May. Leaves died. For some unknown reason, one collapsed in August.

Then, on Halloween, I noticed the survivor had started to grow, really grow. By mid-December, it had formed a second rosette on a thinner stem, lower on the splotchy tan stalk. Both rosettes had green centers signifying new leaves.

I hope it’s not preparing to bloom. They can put out long cones of yellow, ten petalled flowers from the centers of the rosettes in late winter, then die.

Like the lion and lamb laying together beneath a veneer of the commonplace, these plants harbor radically different ambitions from their neighbors. Arboreums may behave like woody perennials in a southern California gardens, but in their hearts they’re like annuals intent on a single chance at reproduction and I’m simply a tool for their use.

Notes:
Baldwin, Debra Lee. Designing with Succulents, 2007.

Baldwin, Randy. "Aeonium arboreum 'Zwartkop'," San Marcos Growers website, on Huntington and Ruth Bancroft gardens.

Kim, Seung-Chul, Michael R. McGowen, Pesach Lubinsky, Janet C. Barber, Mark E. Mort and Arnoldo Santos-Guerra. "Timing and Tempo of Early and Successive Adaptive Radiations in Macaronesia," PLoS ONE 3(5):14 May 2008.

Klingaman, Gerald. "Black Tree Aeonium," Arkansas Home and Garden website, 27 June 2008.

Médail, Frédéric and Pierre Quézel. "The Phytogeographical Significance of S. W. Morocco Compared to the Canary Islands," Plant Ecology 140:221-244:1999.

Valido, Alfredo, Yoko L Dupont, and Jens M. Olesen. "Bird-Flower Interactions in the Macaronesian Islands," Journal of Biogeography 31:1945-1953:2004.

Webb, Philip Barker and Sabin Berthelot. Histoire Naturelle des Iles Canaries 3(2,1):185:1840.

Photograph: Aeonium arboreum from the back, where the dead leaves and new branch can clearly be seen, 1 January 2011.

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