[ Lost in the Landscape ]

21,015 tiny little plants

I now have a new appre­ci­a­tion for the work of field botanists.

A cou­ple week­ends ago I had a chance to work on a rare plant sur­vey on the slopes of Vie­jas Moun­tain in east­ern San Diego County. I enjoy see­ing plants out in their wild habi­tat and the descrip­tion of the task sounded down­right idyl­lic: You go out to trail­less edges of the county, enjoy the scenery, and all the while look for rare plants.

The plant of spe­cial inter­est for this trip was San Diego thorn­mint, Acan­thomintha ili­ci­fo­lia, a plant found only in a smat­ter­ing of places in Cal­i­for­nia and bits of north­ern Baja. And the plant is even more selec­tive than that. It only grows on clay lenses–gently or mod­er­ately sloped areas of clay soil that has washed down from nearby areas. The sur­round­ing chap­ar­ral plants for the most part don’t care for these soil con­di­tions, so they cre­ate open­ings for this rare annual to colonize.

The project was to get a pop­u­la­tion count of thorn­mint from areas where they’d been sighted more than a decade ear­lier. Com­par­ing today’s num­bers against the ear­lier cen­suses would give you an idea of how well the plant is doing in the wilds.

Our assign­ment was pop­u­la­tion 51, a clus­ter of adja­cent stands on the west­ern edge of Cleve­land National For­est, just out­side the city of Alpine. (Look­ing back on the sub­ur­ban sprawl I thought it looked a lit­tle like the pho­tos of Area 51 taken from Free­dom Ridge.)

Most of the spread had burned in one of the recent major wild­fires to go through the county and was in the state of grow­ing back—pretty suc­cess­fully, since travel got to be tough some of the day. When­ever the chap­ar­ral parted and the soil con­di­tions looked right, you scoured the ground for thorn­mints, which at this point in their life­cy­cle were mostly 1–4 inches tall, with most of them not yet in bloom.

One of the three sub-populations we looked at was com­pletely gone. Nada. Zero plants. Maybe the fire wiped them out. Maybe we weren’t obser­vant enough, though we fine-tooth combed the hillside.

But the other two pop­u­la­tions gave us an exer­cise in count­ing plants. Lots and lots of plants. Tiny, tiny lit­tle plants.

By the mid­dle of the after­noon we had a count, 21,015 plants. It was six hours of open slopes with no shade spent in deep con­cen­tra­tion look­ing for the lit­tle plants, count­ing all the while.

I’ll con­fess: We did a lit­tle esti­mat­ing when the pop­u­la­tions got really large, and so we didn’t actu­ally phys­i­cally count all 21,015 plants. But 21,015 seemed like a solid estimate.

While it’s good to know that there are more than a hand­ful of plants left in the wild, it’s also a lit­tle unnerv­ing to see that they have such a lim­ited dis­tri­b­u­tion, and more dis­turb­ing that one of the three pop­u­la­tions from ear­lier seemed to have vanished.

Locally com­mon, but in the grand scheme of things, awfully rare, espe­cially with human encroach­ment from Area 51 next door.

San Diego thorn­mint prob­a­bly won’t turn into one of the great gar­den plants for Cal­i­for­nia native gar­dens. But along the way we saw plenty of species closely related to those used in home native land­scapes: lau­rel sumac (Mal­osma lau­rina), cean­othus (tomen­to­sus and folio­sus), sting­ing lupine (Lupi­nus hir­sutisim­mus), man­zanita (one of the Arc­tostaphy­los glan­du­losa subspecies)…

…and one of my favorite flow­er­ing natives: blue-eyed grass, grow­ing and bloom­ing among the tiny lit­tle thornmints.

Usu­ally my cam­era is the first thing I pack for one of these out­ings, but some­how I for­got it at home this time. My thanks to team-leader Janet for the use of her images from the trip!

May 14 2010 | Categories: landscape • places • plant profiles | Tags: Acanthomintha ilicifolia • native plants • plant surveys • rare plants • San Diego thornmint | 4 Comments »