Re: zone map with cities

**"* T* <m*@hort.net>**

Well, Dan, now that I think about it, using a plant indicator may be
rather difficult because, as you note, soil can make a difference as
well as climate - and aspect.  Another issue is the provenance of the
plant itself.  For instance, while Cornus florida is native from
Canada to Florida, plants propagated from seed set on plants in the
south won't make it through northern winters from what I've been
told.  There are probably other similar instances where plant
populations have acclimatized to a certain local and don't move
substantially north or south well, although the same species and/or
cultivar may do fine if propagated from local material.  TC
propagation - well, I have no clue how that would affect anything,
but would not be surprised if it did.

And, then, of course, there's winter itself.  For several years,
we've had very mild winters; the last two have been bears - this one
in particular.  Weather is cyclical just about everywhere; it's not
set in stone like a zone designation would have one believe.  So that
indicator plant may do well 5 out of 6 winters and that 6th one may
do it in.  

Plants don't read and don't know about zone designations nor where
they are supposed to grow and where they are not.  If conditions are
suitable, they will grow and thrive; if they are not, they languish
and die.  It's really very simple from a plant's perspective...it's
only humans who are eager to classify everything and get upset when
they discover that square pegs don't fit in the round holes of our
zone designations (or perceptions of where what plant should be
growing).  Having something as a rough guide is nice, but IMO we're
tending to place too much importance on a designation that has a very
limited practical use.  

I'd also be rather surprised to find that a true "native" soil exists
anywhere that humans have occupied for the past hundred years or
more.  

Marge Talt, zone 7 Maryland
mtalt@hort.net
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----------
> From: Dan Clost <dan.clost@sympatico.ca>
> 
> Hi again Marge,
> As we all know, temperature alone is not sufficient. However, even
within
> that one parameter little things like relative humidity can affect
the
> survivability of the plant. However, I don't want to belabour that
point
> because it seems that we on this list got into this discussion just
a short
> time ago.
> I am curious about using plant indicators for hardiness maps and
was hoping
> someone on this list has experience with it. It seems that there
are two
> variables that aren't being taken into account.
> One is the plant itself. Is the Amelanchier canadensisof today, for
example,
> the same as 30 or even 20 years ago? Have the plant breeding
boffins
> improved it sufficiently that it might survive in harsher climates?
Do we
> run the chance of altering a zone based on lab work instead of
environmental
> changes?
> The second, a bit more difficult to nail down, would be the growing
medium
> in which our indicator plants are growing. (And any care they might
be
> receiving that would augment their survival.) For example, its all
well and
> good to plant native indicators but can we plant them in their
"native"
> soil?  Does such a medium exist in suburban, or even rural North
America?
> Somedays it just good to be a plantsperson and not have to worry
overly much
> about science, eh?
> Dan

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