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Hot Vegetables
11/06/2002
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.
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