On Sun, 12 Nov 2006 01:31:38 -0500, Steve wrote:
To warp this thread around to something half way serious, I have often
wondered if I am wasting my time pulling and hoeing the weed Purslane.

One serious reason to weed is that most weeds transpire more water
than most cultivated plants. That's possibly ok when soil moisture is
abundant, not so good when water is a limiting growth factor.

In addition, most cultivated plant growth is limited by either available
light for photosynthesis (tall weed problems here), or a shortage of one
or more minerals. If the weeds are tying up the mineral needed, the
crop isn't going to produce like it could.

There are somw "weeds" that are beneficial - for instance, the mosquito fern,
Azolla, has N fixing bacteria; this can benefit unfertilized paddy rice.
But that's not true of most weedy species.

Speaking of weeds, if you'd like a nice tour of weed biology, pick up a
copy of WC Muenscher's book Weeds, preferably an early edition. Ignore
any and all references to chemical control -- most that were used then
are too toxic to even consider now -- but read about the cultural controls
that were used before we had Roundup and similar...

They still work well if we can get people to use them...

Kay