Fwd: Establishing taxa as "present"

Jane McGary janemcgary@earthlink.net
Tue, 02 Sep 2008 11:44:19 PDT
Correct me if I'm wrong, but my understanding is that a plant is declared 
"invasive" in tests if it spreads by self-sowing or rapid root extension in 
a test plot at, for instance, an agricultural experiment station. This may 
be applicable to agricultural situations, but it does not necessarily 
reflect a plant species' potential to affect indigenous vegetation. Indeed, 
native plants can become "invasive threats" when human activity alters the 
balance of nature; for instance, juniper has become dominant in eastern 
Oregon as a result of cattle grazing, leading to degraded pasture and 
increased fire danger.

Every gardener knows that there are many plants we grow that will self-sow 
into disturbed soil, but not into fully vegetated sites. For instance, when 
the acreage next to mine was being run as a Christmas tree farm, with 
herbicide applied between the rows of trees and the soil constantly 
disturbed by harvesting and replanting, some of my trees and shrubs seeded 
in there, such as birches and buddleia. The farm has now been abandoned for 
about 10 years and the trees have grown up closely, and native vegetation 
covers the ground between them, and no new self-sowing is apparently taking 

On my own acreage, the only species I've seen escape from the garden into 
undisturbed soil is a borage, Pentaglottis sempervirens, which was sold to 
me as Brunnera by a small local nursery -- when I was new here and didn't 
know what Brunnera looked like. I spray it every spring but it is difficult 
to eradicate; fortunately, its seeds are large and heavy and don't get far. 
(It's pretty in both foliage and flower. Last year Steve Doonan wanted a 
start of it, and I had to refuse flatly!)

The answer to preserving native biota is to preserve entire communities, as 
large as possible, isolating them from human activity as much as possible 
-- not to forbid the growing of rare species of Dionysia in alpine houses. 
I suppose there are cliffs in Nevada where the dionysias would be invasive, 
though! Indeed, there are probably habitats somewhere in the United States 
where almost any plant from anywhere in the world could take hold, from the 
tundra of Point Barrow to the swamps of Louisiana.

Jane McGary
Northwestern Oregon, USA

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