Re: Hardiness and heat zones

**John MacGregor j*@earthlink.net**

on 6/26/03 8:19 PM, Larry Maupin at larrymaupin@sbcglobal.net wrote:

> As an experienced California gardener, what is your opinion of the Sunset
> zone system? Should we all be adding the Sunset zones to our stories?

Larry,

Of course, the points you make about adaptation to individual microclimates,
maintenance practices, and other local conditions apply to any zone system.
The advantages of the Sunset system are:

1) Scale.  Each individual map is blown up to a much greater size,
permitting far greater detail than the USDA system.

2) Factors considered.  Besides low and high temperatures, the system
includes length of growing season, elevation, seasonal variations in sun and
clouds, humidity, and prevailing winds, rainfall patterns and amounts,
thermal belts, and may other items that go into determining what one can
grow in a particular area.

Unlike you, I garden for a living and write and take pictures on the side.
Before I came to southern California in 1970, I learned to garden in New
Mexico--high and dry--in Albuquerque and Santa Fe, so I came here with a
totally different perspective.  I had to start from scratch and learn all
over again, with an entirely new, vastly expanded set of plants.

Between the coast, the mountains, and the deserts in the Los Angeles Basin
alone--barely 25 or 30 miles as the crow flies--there are vast changes in
elevation, wind patterns, temperatures, and amounts of sunshine and fog.
Moreover, there is a constant battle between desert and marine influences.
During May and June, it will often be cool, cloudy, and drizzly in the 60s
for three weeks (as it was at the beginning of this week), then suddenly
jump to near 100 degrees as a high pressure system builds over the Great
Basin and hot desert winds blow through the passes and canyons (as it did
yesterday), then just as suddenly return to marine influence.  Some version
of this scenario can happen any time of year.  Some people from the east
miss the changes of seasons when they move here.  I often joke that in
southern California we have all four seasons--often in a single week.    The
general pattern is mediterranean, with hot, dry summers and mild,
intermittently rainy winters, but variations can be so marked from day to
day, week to week, month to month, and year to year, that plants are often
totally confused about when they should start growth or bloom.

Before I took the job as chief horticulturist at the Huntington Botanical
Gardens  and settled down in the Pasadena area in 1972, I explored all of
southern California's varied climates on weekends with the Sunset Western
Garden Book in my little hot hand.  It was an intensive, self-taught course
in geography and climatology, and can hardly imagine learning so much
without Sunset as my textbook.

Yes, I am sold on it.  I belong to many internet discussion groups devoted
to many kinds of plants and plant-loving critters, and I own nine of them
myself--dealing with lavenders, geraniums and erodiums, plectranthus,
hummingbirds, etc.  I constantly urge other members to create signatures
like mine with both USDA and Sunset zones appended, because this instantly
tells me a great deal about the conditions under which people garden in an
unfamiliar part of the country.  Now that the Sunset zones have gone
nationwide, it also allows me to look up plants that are likely to do well
in any area.  

Some of the zones in the eastern half of the U.S. may still need a little
tweaking, but in the western half, the editors have had a quarter-century of
feedback and they have listened.   I believe they work very well.  Writers
addressing a widespread audience would do well to use both the USDA and
Sunset zones.

John MacGregor
South Pasadena, CA 91030
USDA zone 9   Sunset zones 21/23

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