Concerning USDA Zones...
Quote:
Originally Posted by ElenaMarie
True, but I also use the zone as an estimate of how much sun a plant can tolerate in my area. Plants listed as full sun to partial shade almost always require deep shade from the summer midday sun. Apparently the sun is quite a bit stronger down here than wherever those light recommendations are made. I killed a lot of plants before realizing that those criteria are NOT made in low-latitude area.  |
You are correct that the sun is a LOT stronger as you move south (I used to live in Georgetown SC, and everyone who visited got sun burn despite our warnings), but the USDA zone is absolutely NOT a good tool for estimating that.
Solar intensity is a function of geographic latitude and altitude, while the hardiness zone is also effected by other factors like proximity to bodies of water, sheltering by hills, mountains, and forests, and the like.
Even though I am at roughly the same latitude as Cheyenne WY, due to altitude, they have a greater light intensity than do I, but I am several full USDA zones warmer than they.
Even going west across SC you'll find at least three sub-zones, but all have pretty similar sunlight levels.
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