All tamarisk isn't the same

  Dear HCN,

"Tackling Tamarisk" (HCN, 5/25/98) lifts the lid on a nasty can of worms, namely the invasion of Western wildlands by alien plants - those dreaded weeds. Paul Larmer credits tamarisks with spreading into "virtually every river system in the West." Could be, depending on the definition of "river system." More to the point is how many miles of rivers are lined with stands of tamarisk? Many river systems have loads of tamarisk in the lower reaches yet are free in the middle and/or upper portions.

Second point is treating several species of tamarisk as a single entity. Certainly there are thousands of miles of good waters unsullied by this curse. Tamarix rammosissimum and its cohorts that form mostly tall shrubs and spread by underground root sprouts are the major culprits. Your photo of the chainsaw-cut trunk is clearly Tamarix aphylla, the athel tamarisk, which makes a good-sized tree, spreads very slowly (if at all without man's help) and really makes a decent ornamental for some areas, although it is tarred with the brush of being a hated tamarisk. One thing is near certain - all escaped Western species of tamarisk don't have the same autecology.

While the change in regimen of Western watercourses has certainly made some ideal habitats for the shrubby tamarisks, I am convinced that if we lacked alien woody plants, native shrubs would be able to fill the vacuum that we all know nature abhors. But, the aliens have landed and we can't turn back. On many a Western riparian zone, should the tamarisks be eliminated or weakened, Russian olive would fill considerable of the gaps. After all, it has naturalized from the Mexican to the Canadian border, and in all 17 Western states. I'd guess that more miles of Western streamsides are dominated by Russian olive than by tamarisks. Which of these two is better or which the worse will foster a great debate.

For a map of the extent of Russian olive's hold on the West, see: "Naturalization of Russian olive in Western United States," Western Jour. Applied Forestry, I(3) 1986. While tamarisks are a new invader to the Snake River Plain in southern Idaho, the spread at this northern limit is rapid. See "Wild Trees of Idaho" (U. Idaho Press, 1995).

And, folks, we haven't touched starthistle, skeleton weed, halogeton, cheatgrass, spotted knapweed, et cetera, et cetera, et cetera!

Fred Johnson

Moscow, Idaho

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