Brook Klehm bklehm@comcast.net
Sun, 21 Aug 2005 20:01:39 PDT
Alberto's reply addresses a really important point and shortcoming of 
the USDA zone system.  The USDA system, refering to average cold 
temperatures, doesn't address the heat requirements of plants.  In USDA 
8, it makes the mistake of lumping the hot and humid, summer wet 
southeast of the United States with the cool, summer dry Pacific 
Northwest.  Needless to say, many plants that thrive in the southeast 
fail to thrive or fail all together in the "other" USDA 8.  Strangely, 
many plants that are listed as hardy to USDA 7 in hot summer climates 
fail here in the coastal mediterranean climate of USDA 9 California.  
We don't get enough summer heat to harden off the woody tissues.  Plus, 
many plants adapted to winter time dormancy go semi-dormant in our dry 
summers and make the mistake of reawakening as fall's cooler 
temperatures arrive, putting on fresh, soft new growth that invariably 
gets nipped by the frosts of October.  Add to that the heat 
requirements of many Central and South American plants (to say nothing 
of plants from the eastern Cape of South Africa)... well, you get the 

Hedychiums, being the example,  may grow well but never bloom in this 
"other" USDA 8/9.  At least Hedychiums produce attractive, lush, 
tropical appearing foliage.  After all, who says a plant has to bloom 
to be a valuable garden plant?

The American Horticultural Society has attempted to address the 
shortcomings of the USDA zone system with a heat tolerance system with 
12 zones and a good bit more detail than the cold tolerance systems in 
use.  It's only a few years old and not in general use yet.  I have 
reservations about it, however, as I do about any system that takes 
into consideration only one variable.  Following that kind of logic, 
you would need multiple maps to decide what plant would thrive in you 
locale.  There would be a map for cold tolerance, for heat tolerance, 
for soil type, for elevation, for rain season, uh... there must be more 
variables to consider as well.  Yeah, there are shortcomings to the 
desire to measure and evaluate everything.  There's a great deal of 
wonder and mystery (even magic?) in horticulture.  Thank goodness for 

Thank you, I'll climb down from my soapbox now.


>>          Brook's mention of Hedychium reminds me of one of my
>> gardening failures.  A certain mailorder seed house in South Carolina
>> sold Hedychium gairdnerianum for several years with glowing praise
>> for the fragrance of the flowers, and the claim that it was hardy to
>> Zone 7.  Well, it has survived for several (7?) years, so I suppose it
>> it hardy, though we haven't had a hard winter for several years.
>> As to the fragrance, that is a little harder to determine, as it has 
>> never
>> flowered.
>>          It freezes down in the fall, starts growth relatively late 
>> in the
>> spring, then grows quickly to about three feet tall, and stops.  
>> Eventually
>> it starts new shoots from the base, which may get to full height 
>> before
>> freezing, or may not.  Right now, in mid August, it has about 6-8 
>> sprouts
>> coming from the base, perhaps 6" long/tall.  It seems unlikely it will
>> flower this year either.  For the last 3-4 years it has been in a 
>> large
>> (5 gallon) pot, so it can get an earlier start in the spring and not 
>> freeze
>> down so early in the fall, but that hasn't helped.  It also has a pan 
>> under
>> the pot, so it isn't stressed for water
>>          Unless someone has some helpful suggestions, this probably 
>> will
>> be the last year for this plant here.  I doubt that I will try 
>> different
>> Hedychiums
>> in the future, given the lack of success with this one.
>> Ken  Z7 Oregon
> Hi:
>    Sorry Mary Sue, but Ken has brought forward a most interesting 
> subject
> and his posting deserves to be quoted complete. Very surprisingly, most
> people fail to realize that if a plant is hardy to a given climatic 
> zone
> lower temperatures this single fact has nothing to do with the rest of 
> its
> cycle. What is the use of having a plant survive the winter if it will 
> never
> grow well or even flower?. Of course, some nursery people is very 
> active in
> informing potential customers of hardiness of their plants but 
> astutely add
> nothing of the rest. Hedychium gardnerianum, mentioned here is rather 
> well
> known in downtown Buenos Aires and the northern coastal suburbs. That 
> is to
> say zone 10 in winter and 10-11 in summer. It behaves as a perennial 
> foliage
> plant (year round) grows quite neglected even quite dry in the worst 
> heat of
> summer and flowers abundantly every year and it does very well in 
> dappled
> shade. From the rhizomes there is a constant although not rampant 
> increase.
> The dark green foliage is sumptuous and the yellow flowers with very 
> long
> crimson anthers are stunning. Although there are other Hedychiums 
> reported
> to be hardy, a climate in which they would not retain their perennial
> foliage and flower regularly is clearly not for such (and scores of 
> other
> plants) although this spoils a good sale. This same plant brought some
> distance into the open land, with a say zone 9 winter has the perennial
> foliage battered by low temperatures and remains stunted.
> Regards
> Alberto
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