"Rob" wrote in message
...

snip
This thread raises an interesting weed-identification issue:
most gardeners want to be able to identify weeds as early as possible
in their development, which normally means BEFORE flowers have formed.
However, most systems (books and websites) rely on flowers for
identification.
/snip

One of my best wild flower books is "the Wild Flower Key" by Francis Rose
(Frederick Warne 1981) which features a useful vegetative key to identify
plants not in flower. An updated edition is still in print (try Amazon).

R.