Tuesday, May 19, 2009

Zoom and Bloom

One of the most extravagant botanical happenings in the southwest deserts is when agaves have mustered the energy to send up their flowering stalk. Their reproductive strategy is known colloquially as "boom and bust" reproduction, because the plant will live for many years as a leafy rosette, (anywhere between 3 and 100, depending on the species) and then shoot up a stalk bearing hundreds or thousands of flowers in one season. Then the entire plant dies. The academic term for this is "monocarpic perennial," which translates to "plant that lives for many years but only produces seeds once." I call it "zoom and bloom."

For the past few weeks we have been measuring a few agaves near our house every day or two to see how fast they zoom. When we started measuring the first one on April 24th, it grew three or four inches a day until a thoughtless vandal snapped the flowering stalk and put an end to the zooming. But in that week it went from 38" tall to 65" tall. The broken stalk is still alive but could not grow any taller since these plants grow from the tips of their stems (the apical meristem, if you want to speak botanese). Today we noticed that, despite the damage, the remaining buds on the lower part of the stalk are beginning to open.

We started measuring two other agaves after the sad day when the first plant was brutalized, one of the same species and one of a different species. (I confess that I haven't taken the time to identify either of them yet. There are over 300 species, and in landscaping it could be any of those, not necessarily a native to the area.) The slim stalked species like the one that got broken has topped out at 115" tall, nearly 10 feet, and is now beginning to bloom. The other is growing even faster, zooming up to 9" per day, with no sign of flower buds yet. Eyeing old stalks of the same species, I'm going to predict that it will zoom up to 15 feet tall before it blooms.

So this is what we do to amuse ourselves during the hottest May on record in Phoenix-14 consecutive days of 100+F highs.
Tune in for the next exciting installment of the Agave Chronicles next week when we begin counting flowers and recording pollinators!

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