Sunday, December 09, 2007

Western Stickseed

What’s blooming: Sweet alyssum from seed.

What’s still green: Conifers, grasses, Apache plume, roses, Japanese honeysuckle, hollyhock, winecup, columbine, lamb’s quarter, rockrose, California poppy, coral bell, snapdragon, beardtongues, bouncing Bess, blue and yellow flaxes, sea pink, yellow and pink evening primroses, catmint, Rumanian sage, vinca, tansy mustard, sweet alyssum, western stickseed, white sweet clover, sweet pea, sea lavender, yuccas, red hot poker, iris, Saint John’s wort, snakeweed, coreopsis, anthemis, chrysanthemum, tansy, Mount Atlas daisy, Shasta daisy, perky Sue, Mexican hat, purple aster.

What’s gray or gray-green: Salt bush, winterfat, buddleia, loco, snow-in-summer, pinks, fern-leaf yarrow, golden hairy aster.

What’s red: Cholla, soapwort, hartweigii.

What’s blooming inside: Aptenia, geranium.

Animal sightings: Usual red-sided birds and quail continue to feed.

Weather: Cold, clear nights early in the week iced over standing water along the road; more recently, clouds moved in to scatter droplets at sundown; rain yesterday; more rain and a little snow last night.

Weekly update: Whatever is a spring annual like western stickseed doing germinating in my driveway now, when other plants are either going dormant or dying from the cold? Normally, I see the basal rosettes emerge after March 20th and start flowering the second week of April.

It’s a question that puzzles botanists like Kathy Freas and Paul Kemp, who know desert annuals sprout when there’s enough moisture at the right temperature. What they wonder is how does a species survive when a cool temperature plant like Lappula occidentalis germinates just before a drought or severe cold that kills seedlings.

When they compared plants that germinate in the heat of summer when moisture is more reliable in the Chihuahuan desert with those like stickseed, they found the cool-season plants had developed genes that controlled dormancy, while summer plants had not.

Dormancy allows plants to build seed reserves which can sprout when conditions change dramatically. Stickseed is one of the first plants to arrive after a fire, stays long after the soil has been trampled by cattle.

For years, western stickseed pushed up thin stems with tiny, five-petaled, bluish-white flowers. Those stalks would unfurl, much like their forget-me-not cousins, to produce more color on top while hairy, green balls replaced spent blooms. The taproot could send up multiple, sparsely leaved columns, but usually they remained small, delicate plants that crept along the edges of garden beds.

Then, in 2004 the upper yard was covered with clumps where the ground had been disturbed in 2001 to bury a natural gas line. That area had been colonized by muhly ring grass until the drought of 2002-2003. The flowers were equally prolific in 2005, but since, the annuals have put out fewer and shorter racemes.

Perhaps the seed bank has been exhausted, although seeds are the one thing I know have been produced abundantly. The hard, odd-shaped dark seeds start to form in May, and attach themselves to my socks and pant legs in June. They remain a nuisance after the plants have dried into brittle stalks, enough to keep me out of the area where they’re growing and, coincidentally, protect the nearby soil.

It’s just been in the past few weeks, the very time that the vagrants have been growing in my drive, that the dead clumps have disappeared, probably broken off by the high winds and blown elsewhere to drop whatever barbed seeds remain.

The plants may have been shunted aside by snakeweed which also appeared in that area after the drought, and is not polite enough to quietly leave at the end of the season. Or, the tiny Lappula may not have liked the higher levels of rain and snow in the past few years.

It’s impossible to predict what will happens next year; the crop is too dependent of whatever combination of temperature and water exists in early spring. All I can do when I stop to open my gate is look for the white-haired volunteers to see how long they survive the coming cold.

Freas, Kathy E. and Paul R. Kemp. “Some Relationships Between Environmental Reliability and Seed Dormancy in Desert Annual Plants,” The Journal of Ecology, 71:211-217:1983.

Photograph: Two western stickseed seedlings, 8 December 2007, with tansy mustard in back.

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