BSBINews - BSBI Archive - Botanical Society of the British Isles

Aliens - Botanical delights at Seafield Park (v.c.ll) I Urtica membranacea Poiret in v.c.29. 33
One of the other species seen, Xeranthemum
annuum was so unusual that it was not recognised
by 'MapMate', and may well have been
new to Hampshire altogether. Unfortunately
I have not yet found time to see what has come
up here this year. On last year's evidence it
may be better to wait until August or September
before doing so.
Urtica membranacea Poiret in Cambridgeshire, v.c.29
MAN C. LESLIE, 109 York Street, Cambridge, CB1 2PZ
Two sites for the annual Mediterranean nettle
Urtiea membranaeea have recently been
discovered in the city of Cambridge. The
details ofthese finds are as follows: a) numerous
plants in crack between pavement and the
front wall of the Sir Isaac Newton public
house and the adjacent hair salon ("Lyndsey
McDermott"), Castle Street, Cambridge,
(52/44415933), 22 nd March 2009, A.C. Leslie
- later discovered to be in smaller quantity in
car parks behind these buildings; b) numerous
plants in cracks between pavement and the
brick wall of a house on the east side of
Herbert Street, at its southern end (the building
is actually the side of 187 Chesterton
Road), Cambridge, (52/45465955), 29 th
March 2009, A.c. Leslie (CGE) , also
scattered on either side of Herbert Street as far
as numbers 16 and 17, as well as around the
base of an Aeer negundo (Ashleaf Maple)
planted in the pavement at the south end of the
street.
In BSBI News 103: 29-30 (2006) Ann
Boucher and James Partridge described apparently
the first British record for this alien
nettle, made in April that year from a street in
Warwick (v.c.38), in circumstances clearly
very similar to those described here. In the
Cambridge sites, the species seems naturalised;
both populations are best developed at
the base of warm, west-facing walls and their
early flowering may mean they have a fighting
chance of setting seed before the first wave of
Council spraying. There is no evident source
for the plant in either place and the spread of
plants locally suggests they have been in each
site for a couple of years at least. The illustrations
in BSBI News 103 show the characters of
the plant well. The following is a description
taken from the Cambridgeshire material:
An erect monoecious annual; stems 3-40cm
tall, simple in very small plants but otherwise
often with spreading-ascending branches from
the base, often purple in full sunlight, with
sparse, simple, rather weakly stinging hairs.
Leaves broadly ovate, up to 77x75mm (but
often much smaller), truncate to cordate at the
base, deeply and sharply toothed, a rather deep
almost glossy green above, ciliate, the upper
surface with sparse, spreading, long, stinging
hairs and rather more numerous, very short
simple hairs, much less hairy below; petioles
from about half as long as the blade to longer
than the blade in mid-stem leaves. At the
nodes, on each side of the stem, is a pale, ovate
stipule, up to 7mm long, sometimes bifid at
the tip, which is interpreted as the result of
fusion between stipules from each opposing
leaf. The clustered, unbranched, erecto-patent,
terminal male racemes much exceed the
petioles and are often tinged purple, making
them conspicuous, especially when contrasted
with the white anthers; the male flowers are
borne unilaterally on an expanded, pale green
membrane (hence the specific epithet); on
vigorous stems there will be whorls of male
racemes at one or two nodes below the apex
and these can be longer and curve downwards.
The much shorter, spreading to sharply
reflexed, female racemes are borne below the
male flowering nodes. Flowering March to
April.
Despite searching the area around and
between these two sites no other plants have
been found. However it seems likely that this
species may be overlooked elsewhere both
within Cambridgeshire and elsewhere in the
British Isles. A hybrid with U. urens
(V. xtremolsii Sennen) is claimed in Spain
and might be the next target to aim for!