Martin Brown wrote:
[...]
I would be a lot more inclined to base planting time on the local
weather.

If you insist on planting at say "full moon" (or any other specific
lunar phase) you are stuck with either planting 2 weeks too early (and
risk see everything lost to a late frost) or two weeks too late getting
a poor crop.

Not that two weeks either way usually makes a big difference, but I
think you're right: these ideas may simply date from times when people
didn't have calendars, and couldn't have read them if they had. I can't
imagine any mechanism by which the moon would significantly affect
plant growth*. But the idea's proponents are persistently keen on it: I
prefer to remain cautiously open-minded about it till there have been
lots of good experiments.

*(And I'm always fascinated to think that people who reject religions
which have been carefully thought out by first-class minds over
hundreds of years can be tempted by primitive superstitions and such.)

--
Mike.