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Re: Re: temperatures and hardiness

Marge-I'm with you on the whole deal. If a plant is listed as hardy from
zone 3-8, I don't even bother. I can almost guarantee it's too hot for it
here. I try and stick with zones 5-9. I'm supposedly in heat zone 8, but so
are many other places that don't have our 3 am humidity and temps. Sometimes
very frustrating!

I do rely heavily on the Southern Living Garden book (MUST get the new
edition) as it rates things from upper, mid, lower, coastal, south etc. So
far it's worked well for me.

Andrea H
Beaufort, SC

----- Original Message ----- 
From: "Marge Talt" <mtalt@hort.net>
To: <gardenchat@hort.net>
Sent: Monday, April 12, 2004 7:15 PM
Subject: Re: [CHAT] Re: temperatures and hardiness

> Well, the USDA hardiness zones are just the tip of the iceberg.  They
> only deal with average low temperatures for given locations, not with
> all the other factors that determine a plants cold hardiness.  It's
> somewhere to start, but *only* a start.
> The AHS heat map is, IMO, completely useless.  As pointed out, it
> only shows the avg. number of days above 86F.  Whoopee!  Nothing at
> all about night temperatures nor humidity - two very important
> factors in whether a plant can survive.  Useless, useless, useless.
> Actually really annoys me that they published this and are making
> such a big deal of it (or trying to).  If it were really useful, that
> would be one thing, but it is not and as it stands it never will be -
> not to mention that only a minuscule number of plants have been rated
> according to that map.
> The USDA zones do help you figure out whether something has a prayer
> of surviving where you are because of cold.  If a plant is rated z9,
> someone in z4 needs to forget it in the open garden.  What I have
> learned is that most plants rated as hardy in z3 are not going to
> like summer in z7 - no matter whether the designation is z3-8 -
> having killed quite a few with that type of designation.  They might
> survive nicely in z 7-8 PNW but they ain't a gonna make it in the
> Mid-Atlantic or northern Alabama nor Texas.
> More to the point is where does the species plant originate?  What is
> its provenance?  If you know that, you can do a bit of research about
> the climate of that area and compare it to yours.  This is, still
> somewhat of a generalization because elevation makes a real
> difference; some plants from places you might think tropical just
> looking at a world map, come from very high elevations and are quite
> cold hardy - they might not be able to take hot, humid summer nights,
> but they survive cold winters.  Whether a plant comes from a winter
> dry or winter wet climate also makes a big difference - same with
> summer.  And, we must not forget our own garden micro-climates.
> Some plants are quite hardy in hot summer climates that are not in
> cooler summer climates (the UK, for instance) because they need a
> good long hot period to ripen.  Many plants you read about in English
> garden books say they need a warm wall to survive; given that where I
> am or where Pam is, they'd fry.  Many of our ornamental grasses are
> considered borderline hardy in the UK because it just doesn't get hot
> enough in summer for them....Miscanthus is one - bone hardy for me
> and in much of the US; hardly ever blooms in the UK.
> Some plants are quite hardy if given sufficient time to adjust to
> cold weather but will die fast when hot weather turns cold overnight.
>  Conversely, some plants are actually hardy, but tend to start
> growing at the first sign of warm weather in spring and get zapped by
> roller coaster spring frosts...think Hydrangea mac.  This has to do
> with how a plant develops its winter anti-freeze; some do it
> according to temperature and some according to day length; think some
> even combine these.
> Some plants are native and hardy throughout much of the US, but it
> makes a difference where they originated.  For instance, Cornus
> florida (dogwood) born and bred in the south will not be hardy in the
> north - even from seed.  So a "zone" designation for this plant,
> while interesting, does not tell you whether the plant in your hand
> (or your local nursery) is going to live through your winters.
> That said, you will never know whether you can grow a plant until
> you've tried and killed it at least 3 times, even one supposedly
> rated hardy where you are.
> </dismount zone soapbox>
> Marge Talt, zone 7 Maryland
> mtalt@hort.net
> Editor:  Gardening in Shade
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> ----------
> > From: james singer <jsinger@igc.org>
> > Sorry. Kitty got part A right. A-Z tries to fit plants into USDA
> [cold]
> > zones. And Noreen got part B right, A-Z's understanding of low
> > temperatures appears to assume a period of duration that does not
> > pertain, at least not in Zone 9 or above. It may or may not pertain
> in
> > lower zones, but I have no useful experience with them.
> >
> > On Monday, April 12, 2004, at 05:48 PM, ""
> > <gardenqueen@academicplanet.com> wrote:
> >
> > > You're right Cathy - the AHS heat zones are based on average
> number of
> > > days per year above 86 degrees. I've got the big map on my wall
> right
> > > here in my cubicle so I'm reading right from it.
> >
> > Island Jim
> > Southwest Florida
> > Zone 10
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