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Hot Vegetables
Fri Nov 18, 2005
Listen in RealAudio 
Glamorous plants like orchids and roses look like they would be picky about weather
but it turns out that sturdy workhorse vegetables also have their decided
meteorological preferences.
Hi, I'm Bryan Yeaton for The Weather Notebook.
Crank the air and soil temperature up too high, and peas peter out, producing empty
spaces between abundant peas or no peas at all. Leafy crops like lettuce and spinach
"bolt"-race through their growth cycle when temperatures are high and days long --
bent on going to seed; their tender curly heads acquire ugly necks and a white sappy
substance that makes the leaves taste bitter. Tomatoes, on the other hand, will sulk in
their hard, green skins all summer unless they get a nice long run of hot days and
warm nights. Peppers also like it hot; try growing them in a place like Northern Maine
and you end up with something as long and skinny as a cucumber (another heat
addict).
Weather-obsessed gardeners have long known about the US Department of
Agriculture's Hardiness Zones, numerical categories that indicate minimum winter
temperatures, from below –50F in Zone 1 (for example Fairbanks) to above 40 in Zone
11 (Honolulu). But if you want to know whether your tomatoes will ripen or your lettuce
will bolt, you may find the American Horticultural Society's Heat Zone Map even more
useful. This map divides the nation into 12 zones based on the average yearly number
of "heat days" when temperatures climb above 86. According to the AHS, 86 was
chosen because that's "the point at which plants begin suffering physiological damage
from heat." Or, in the case of tomatoes and peppers, when they really start to relax and
enjoy themselves.
Thanks to David Laskin for today's story. The Weather Notebook is produced through
generous grants from Subaru and The National Science Foundation.
Today's Links
Heat Zone Map
http://www.ahs.org/publications/heat_zone_map.htm
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