In message , Sacha
writes
On 2012-07-02 18:43:13 +0100, David Hill said:

On 02/07/2012 17:58, Sacha wrote:
On 2012-07-02 17:49:46 +0100, Stewart Robert Hinsley
said:

In message , Jake
writes
On Mon, 02 Jul 2012 14:39:27 +0100, Spider wrote:

This is, I believe, the identity of the weed which perniciously
invades
part of my garden.
http://en.wikipedia.org/wiki/Whitetop
http://www.unce.unr.edu/programs/sites/tallwhitetop/

http://jennwarren.hubpages.com/hub/C...oxious-Weeds-I
n-Your-Lawn-and-Garden
Sorry for all the links, but this weed has been the bane of my
for
30 years. I *may* be just starting to see its grip loosening. I've
even risked planting that part of my garden again (except for one
corner). Previously, I've never dared move a wanted plant from that
area of the garden to another for fear of spreading it. I dream of the
day I never see another leafy spring rosette. Pedipalps crossed.
Oh dear. TBH, I've never heard of this weed being found in the UK
before. I must lead a very sheltered life.

There's a largish colony by a canal bank a couple of miles away
from
me, but it's scarce of much of the country. It tends to be
southeastern and coastal.
Cheers, Jake
=======================================
Urgling from the East End of Swansea Bay. We don't yet have a
"dah dah dah dah dee dee deeee" theme tune but we're working on it.
There are a couple of recorded sites at the east end of Swansea
Bay,
but there could be less than 50 sites in the whole of Wales.
It would appear that Spider has a rarity and should now go into
high
reverse with eradicating it!! I've never seen it before and thought it
looked quite attractive...
Not such a rarity Sacha, see the map in this link
http://www.brc.ac.uk/plantatlas/inde...ecies-name-329
David @ the very wet end of Swansea bay, where it's been raining
almost all day.

Is this a relative of the weed we have far too much of down this way?
It's the one people here call "shepherd's purse" with the seeds that
'ping' off in all directions the second you touch a pod. It has little
white flowers and seems to bloom at all stages of growth. Afaik, it's
bitter cress but I could have them muddled up.

They're all crucifers. Which crucifers are more closely related to which
other crucifers is not an easy question.

The closest relatives of the pepperworts (Lepidium) are the swine
cresses (Coronopus) - the latest botanical opinion sinks Coronopus in
Lepidium.

Cardamine hirsuta (hairy bitter cress) is a likely identification for
the weed that has seeds that ping off when you touch a pod. But I would
be surprised to see it called shepherd's purse - it has long narrow seed
pods, unlike the obcordate seed pods of Capsella bursa-pastoris
(shepherd's purse) which do have an appearance that one could describe
as purse-like.
--
Stewart Robert Hinsley