Weedy bulbous plants

AW awilson@avonia.com
Wed, 24 Nov 2010 21:18:24 PST
Dear Diana,

You mention the threatened policy of USDA "if a plant was weedy or invasive
in one situation they would ban it for the entire country". That's an
unfortunate choice although it is understandable if you are considering
importation of a species new to the country. Once it is in the country there
are far fewer limitations on its travel. Australia and New Zealand have
similar and extremely tough laws on the matter.

Regarding the USDA  gathering bulb information from our list, there is
information already within it regarding weedy bulbous behavior. For
instance, the Photo & Information section says "Oxalis pes-caprae, known as
the Bermuda Buttercup, has become a major weed in many Mediterranean areas
of the world". If they look outside our site, the Jepson Manual describes
the same species as 'a pernicious urban weed' within the state of
California. Online, if they look at the site of an organization that deals
with weedy species     
they'll find plenty to whet their interest in the way of weedy bulbs in the
garden and bulbs escaped into the wild. I think it would be naïve to think
that PBS's modest contributions to this large subject could determine
whether the USDA decides to ban or admit a new bulbous species. That being
the case, I believe we should be direct and accurate in the descriptions of
the bulbs. The Wiki provides many growers with access to valuable data to a
huge number of species; we should maintain its high standards, reporting
information that would assist those growers for all bulbs, including those
that can be weedy in certain places.

You mentioned that O. convexula does produce bulbils for you. I am assuming
this is indoors and/or with potted plants, as you refer to the use of a
vacuum cleaner. Outdoors, and with plants in the ground or among scree, this
method would be quite ineffective. I find that outdors, the tiny bulbils do
not blow around in the wind, but are washed into cracks and crevices by dew
or rain. That does not make the solution easy. This year has been unusually
wet here early in the season, so that real care has been needed to ensure
that seedlings were plucked out before they reached bulbil stage - some
showed blooms but I got there in time. Tedious.

Andrew Wilson
San Diego

Dear Jim:

>Perhaps I am needlessly paranoid about the 'Invasive Plant
 Police '<

You are not "needlessly paranoid".  Work is progressing on the government's
proposal of a White List of approved plants.  If a plant is not on the list,
it is automatically banned.  I was casually asked by my agricultural agent
last year if banning Oxalis would hurt my business.  I don't think that
question came out of the blue.  The White List proposal has been extensively
discussed on this list, and I remember well a couple of years ago a
representative of the USDAA saying emphatically that if a plant was weedy or
invasive in one situation they would ban it for the entire country.  I think
Lantana and the problems it has caused in Hawaii was cited.  When the USDAA
gathers information, you may be certain that it will refer to this list for
bulb information, so coupling the name of a bulb with the epithet weedy or
invasive could be used as justification for banning it.

In this climate all kinds of things self sow with great vigor, including
Verbascum, Verbena bonariense, feverfew, borage and virtually anything that
produces copious seed.  Not Oxalis, though.  I used to throw my surplus
Oxalis bulbs on the ground outside the greenhouses, where they would form
lovely little mats throughout their first winter, never to appear again.  I
live surrounded by pasture.  Not one garden plant has ever appeared in the
adjacent pastures whereas they sow themselves vigorously in my garden.

We should be very, very careful in how we describe plants that make
themselves at home in our gardens and neighborhoods.  I don't even cosider
O. pes-caprae invasive.  I have never seen it invade pastures or natural
areas, it is mostly present in gardens and disturbed areas in California. 
Most people don't like it because it competes visually with plants they want
to grow.  It does not out-compete them and drive them over the brink, in
fact it only thrives where there is little to compete with, and I speak from
first hand experience.

A tip for dealing with aerial bulbils produced by O. convexula and others. 
Vacuum them up before they have a chance to blow around.  A small hand held
vacuum works great.  I do this so that they don't get in the adjacent pots.


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