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Re: Plants along beaches

>   In my garden, though, I like to grow all sorts of things, plants from
>all over the world. But I don't want to be the next well-meaning gardener
>who unleashes an environmental weed. What can I do to prevent the unwanted
>spread of plants which might become problems outside the garden?  How do
>you other gardeners balance the need to preserve flora native to your areas
>against the desire to grow exotic species in your gardens?
>
>    Elizabeth Morgan, on Tasmania's east coast

Elizabeth --

This is a subject that's dear (?) to my heart, having spent literally
hundreds of hours working with a volunteer crew removing invasive exotics
in the Santa Cruz mountains here in coastal California.  I, too, am
interested in growing exotics, and am equally concerned about the
possibility of unleashing ecological  problems.  Here are two rules of
thumb that I use when dealing with plants whose interaction with the native
flora/fauna are unknown:

1) Never plant anything whose seeds are distributed by the wind (such as
most plants in Asteraceae/Compositae, and most grasses), or which produces
berries that might be attractive to birds.  These are the worst spreaders,
and from even an urban garden can quickly move to the countryside and get
out of control.

2)  Watch carefully for volunteers in your garden, to see what kinds of
conditions the seedlings require.  For example, here where we can expect a
prolonged summer drought, I have a section of the garden that I give summer
water, and a section that gets only what falls from the sky (i.e. virtually
no water from May through October).  Any volunteers that can make it in the
parts of the garden which aren't watered by me are potential problems, and
they (and their parents) have to go.  (This can be tricky, and close
observation can pay off.  For example, in my backyard there is a large
patch of Chasmanthe floribunda, planted in a neat row by some previous
tenant.  In the yard next door is a random group of the quite similar
Chasmanthe aethiopica.  In my yard, C. floribunda does not self-sow; C.
aethiopica has seeded itself with abandon over both yards.  If I were to
plant a  variety of Chasmanthe in the future, I'd make sure it was C.
floribunda.)

In my opinion the bottom line is, if it's invasive, don't grow it, no
matter how nice a plant it may be.  French broom (Genista monspessulanus)
has one of the most heavenly fragrances in the world, and its brilliant
yellow flowers are certainly attractive; but it's a ferocious weed around
here, and I would never consider planting it.  Likewise with any type of
Hedera, which as I can attest from personal observation can actually kill a
mature redwood.

The flip side of this is the "only grow natives" school of thinking.  I
have serious problems with that philosophy, not only from a horticultural
viewpoint, but also from an ecological stance.  I won't get into that here,
though, since this message is already pretty long, but if you'd like to
have that discussion, please let me know.

Hope this is useful.

Phil Stevens
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