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Because it was initially divided into 13 zones. In 1990 they subdivided each zone into a and b zones. I'm not finding any rationale on why subdividing instead
by VyseofArcadia 2y ago
Because it was initially divided into 13 zones. In 1990 they subdivided each zone into a and b zones.
I'm not finding any rationale on why subdividing instead of renumbering, but it probably alleviated confusion at the time. If you're in zone 6b, but you're used to thinking of yourself as zone 6, you're still mostly right even if you forget whether you're in a or b. Easier to remember than suddenly you're in zone 13.
- jellicle 2y ago"This plant is zone 6" "Old numbering or new numbering?" "I don't know, just says zone 6" If you reuse your numbering system, you have to specify which version you're using. Using an all-new numbering scheme eliminates that.
- justsid 2y agoIsn’t it the exact opposite? If it just says zone 6, it’s the old system because no a or b suffix. If the number space got doubled zone 6 would still exist but mean something completely different now. You can’t tell if it’s the old or new system at all because the first numbers all got re-used but with different meaning.