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Aliens - Habitat of Cochlearia megalosperma naturalised in Britain 29
ALIENS
Habitat of Cochlearia megalosperma naturalised in Britain
MICHAEL BRAITHWAITE, Clarilaw, Hawick, Roxburghshire, TD98PT
Cochlearia megalosperma (Maire) Vogt
(Cochlearia glastifolia L. var. megalosperma
Maire (Tall Scurvygrass), which is endemic to
Morocco and south-east Spain, has been
reported in Britain as "well naturalised by road
at Humbie Kirk (East Lothian), found 1994,
also in cultivated and waste ground in Notts.".
It is reported as having first come to be
naturalised in Britain by escaping from the
Pharmacy Garden on the University of
Nottingham campus, to where it had been sent
as seed from a collection at Gatersleben. The
source of later colonies is not known, but it
was being offered for sale by Salley Gardens
organic herb nursery, which is not far from the
university and had obtained seed from there.
This species has now been found naturalised
by the River Tweed at Tweedmill in v.c.S1
Berwickshire (NTS4), on rocks dripping with
water, apparently at variance with this suggestion
of a ruderal habitat, so comment seems
called for.
A series of superb images of
C. megalosperma in Spain is presented in the
Flora of Almeria web site at http://www.
floresdealmeria.comljoyas/cochlearia-megalosperma.
html. Here it is depicted growing
by a tiny rocky stream in the hills in more or
less immediate contact with the water (noted
to be a rare habitat in Almeria). This is not
unexpected for a plant that can grow as an
annual or short-lived perennial to l.S-2.0m in
a season.
The Tweedmill plant was first found in 2006
by Georgina Hargreaves when salmon-fishing
with her husband. It could have been carried
to this site by the extreme floods in October
200S, but the ghillie's recollection suggests it
may have arrived a few years earlier. The
excellent photos she sent me in 200S, when
she saw it again in greater quantity, showed
that it was growing on rocks, but not that they
were especially wet (see Colour Section, Plate
3). I did not visit the site until2S th April 2009,
when I noted: 'It is rather amazing. There are
great patches of the plant, typically Sx 1m each
along lS0m of a dripping, crumbling rock
face, cut by gullies, where most of the plants
are. The whole is more or less shaded by
trees. The plant seems to have been spreading
fast, but to have now colonised almost all the
suitable habitat at this locality. Associates
include Eupatorium cannabinum (Hemp
Agrimony), Cardamine amara (Great Bittercress),
Chrysosplenium oppositifolium
(Opposite-leaved Golden-saxifrage) and
Impatiens glandulifera (Himalayan Balsam).
Stems are already 1m tall and the dead stems
from last year are consistent with the height of
1.S to 1.Sm reported to me. This is a rare
habitat and there was no sign of the plant in
dryer habitats nearby'.
Humbie, v.c.S2 (NT46) is not too far away,
so I visited the site for C. megalosperma on
26 th May 2009 to see the habitat there for
myself. The plant was up to 2.0m high and
just coming into flower, and was growing
luxuriantly at the immediate foot of a wall 3m
tall (it is the wall of a former walled garden)
for about SOm. There was noticeable percolation
of ground water in a number of places
from the bank behind. These places were just
where the Cochlearia was growing. There
was no spread into the verge adjacent to the
wall, which was dominated by Symphytum
tuberosum (Tuberous Comfrey). There is a
wooded dean close by with a variety of good
habitats. I saw plenty of S. tuberosum there
too, but there was no sign of the Cochlearia.
The C. megalosperma habitat at Humbie,
with its dripping stone, thus has many similarities
with the Tweedmill site. In addition, both
are sheltered and more or less south-facing, so
they are places that tend to be warm, and this
may favour a plant from southern climes,
which needs to ripen seed that will germinate