Friday, September 26, 2008

Century Plant in Bloom

We have a relatively rare botanical event going on in the University of Connecticut greenhouses right now: an Agave, or Century Plant, is in bloom. This plant is probably Agave filifera ssp. schidigera, a native of Mexico, but I'm not entirely certain of the identification. The plant has been in the greenhouse at least since the staff started keeping careful records in 1985, and its origins are uncertain. It's got an impressive inflorescence, at any rate, about 12 feet high, with hundreds of greenish flowers opening sequentially from the bottom to the top. The flowers literally drip nectar, and have an odd vegetable smell, sort of like steamed artichokes.

This is the first time this plant has bloomed in its 23 plus years, but "Century Plant" is clearly an exaggeration. Agave plants are monocarpic, which means that the plants cease growth and die shortly after flowering and setting seed. Many Agave species produce vegetative offsets or runners, though, so only the individual rosette that sends up an inflorescence croaks, while a ring of clones around it survive. Our Agave filifera hasn't produced any offsets yet, so it may be gone for good after putting on its show. I'm attempting to self-pollinate it, but it isn't always possible to set seeds with only one plant.

Century Plant blooms are fairly rare in northern greenhouses: at UConn, we keep about 20 agaves, and have had only this single flowering in the past 10 years. In warmer, drier parts of the country, Century Plants--especially Agave americana--are grown as bedding plants, and flowerings are commonplace in suburban gardens and highway plantings.

Tuesday, September 23, 2008

Conophytum minusculum: The Minuscule Cone Plant

Conophytum minusculum in September, still in summer mode apart from the flowers. These plants are an informal cultivar named “Roseum” with particularly intense floral coloration, derived from material collected by plant explorer Frank Horwood.

Mid-September is the peak season for Conophytum flowers, and for a brief interlude my collection looks something like a very small version of the poppy fields in Oz. Cono flowers tend to be incongruously gaudy compared to the compact, often camouflaged vegetative portions of the plants. The flower/leaf mismatch is particularly extreme in Conophytum minusculum, which has succulent leaf pairs the size of match heads, which sport violet to dayglow pink flowers easily five times as large.

Conophytum minusculum hails from the southwestern parts of the range of the genus in South Africa, which means it is adapted to a relatively mild Mediterranean climate, rather than hard desert. The plants grow in crevices and among mosses and lichens on sandstone outcrops, in a scrubby vegetation type peculiar to the Cape region called fynbos. Fynbos occurs on sites with poor, acidic soil and winter rainfall. Fynbos is subject to fires every decade or two, though it seems unlikely that the rocky, barren niches that Conophytum plants favor ever burn directly.

Conophytum minusculum is a definite cool-season grower, and tends to be even more strict about seasonality that other conos. Although the plants flower in the early autumn, the new leaves often don’t take up water and emerge from their summer sheaths until it really gets cold and dreary in November or December. In cultivation, I water the plants more than usual for winter growing South African succulents, enough to keep the soil evenly moist from flowering, through the fall and winter, up until the point where the leaves yellow and dry up for the summer dormancy in April. The plants need as much sun as possible in winter. During the warmer months, I keep my C. minusculum pots in partial shade, and do not water except for a light misting every few days. Summer misting should be just enough to barely moisten the surface layers of soil, which prevents possible losses from sunburn.

The soils where C. minusculum grows in the wild are particularly thin and low in mineral nutrients, and under glass the plants do well in shallow pots, with a gritty, impoverished soil mix. If I were really on top of things, I’d water them with rainwater, though the tap water here in eastern Connecticut seems to be sufficiently clean and low in salts. The plants are well suited to cultivation in New England; famous succulent growers in the Southwest have trouble getting C. minusculum and its relatives to thrive, because of their relatively hot, dry weather and hard, salty water. But the plants thrive here in Swamp Yankee country.

Conophytum minusculum is mostly propagated by cuttings, which establish easily in fall or winter. Seed is hardly ever available: the flowers aren’t easy to pollinate, and even successful pollination tends to result in only small numbers of seeds.