In article , Alan Gould
writes
In article , Kay Easton
writes
But what I was asking you is are you aware of any greater taxonomic
confusion among the brassicas than among other plants (other, of course,
than the problem of common names which have never attempted to mirror
taxonomy and which may be used by different parts of the country to
refer to different plants)

They also vary from country to country. The point I have already made is
that whatever the common name of a plant may be, or for that matter
whatever its taxonomic name is, a gardener needs to know which plant
family it belongs to in order to carry out correct crop rotations.

But there are two points there - firstly the same common name may be
applied to plants of different families - like gillyflower, for example

Secondly, although in many cases closely related plants share similar
growth preferences this may not always be true, where, for example, they
have come to occupy different habitats, and secondly, similarity of
growth preference does not imply close relationship. So removal of plant
from a particular family would not mean that you had to alter its
position in crop rotations - unless, of course, generations of gardeners
had got it wrong!


--
Kay Easton

Edward's earthworm page:
http://www.scarboro.demon.co.uk/garden/