Changes in the status and distribution of Oenanthe pimpinelloides in Essex
two of these, one to a housing estate, the other to scrub, but in the remaining field it is still abundant
over an area of around 1.5 hectares. Then, in 1989, Rodney Cole and Roger Payne reported two
large patches extending over at least a hectare, on a Claygate Beds landslip on the southern slope of
Hawkesbury Bush, Basildon. Meanwhile Stephen Rothero had found a dozen or so plants in an old
roadside grassland remnant elsewhere in Basildon. Since then additional sites around Epping,
Basildon, Clacton and more recently Shoebury have been discovered, together with new sites on
several Essex Wildlife Trust reserves, where it has been either inadvertently or intentionally
introduced with green hay. Unfortunately, any change in distribution due to climate change is being
masked by the spreading of seed using Combi type grass harvesters and verge flailing machines,
together with the deliberate but dubious introduction of this poisonous plant to additional hay
meadows using Combi loads from meadows with it in the sward. It has the remarkable ability to
resist complete removal by cutting machinery, the springy rather woody stems tending to bend flat
rather than be cut, and if it is cut off at hay making time it rapidly sends up a new set of flowering
stems. Even with a late June/July cut, the copious seed heads are ripe enough to be liable to become
entrapped in machinery or tractor tyres. It has one micromoth that is specific to it, Depressaria
daucella D. & S., first found in 1842 between Walton-on-the Naze and Brightlingsea, further
confirmation of the plant's early presence on the Tendring Plateau, and more recently by Reg
Arthur at Clacton in 1995, and a further record from Plaistow by G. Martin in 2000, suggesting that
we may be missing a colony in the east end of London.
It is extremely difficult to distinguish current records of 'native' sites from recent introductions or
recent natural spread. Obviously new colonies on North Weald Airfield, could somehow have
arrived naturally from seed at Epping, but the few plants at Upshire Green and Bird Green, Willingale,
are more obvious accidental introductions, the former from a machine used on Sheppard's Meadow,
and the latter from a meadow mix around the new reservoir. The large patches on a scrubby south-
west sloping pasture on the site of the old Havering Park, must surely be of long standing, despite
their recent discovery. The dense patches in the triangular meadow east of the lake, at the Phyllis
Currie reserve, however, are the result of a recent introduction from the Clacton site, using grren
hay spread onto lake dredgings, and it is also rapidly spreading across the meadow to the south of
the lake.
In Basildon, the story is even more complex. The first colonies discovered on the scrubby southern
landslip slope of Hawkesbury Bush, on the seepage just below the Claygate Beds/London Clay
junction, have probably been there since at least the 1800s. These however began to spread rapidly
along the sides of a new track, striking out to the west, and have subsequently colonised two
adjacent (Johnson's) meadows since 1989. Colonies along the verges of Staneway at Langdon
Hill's and Nethermayne at Vange, have increased in recent years, and extensive colonies are known
in Gloucester Park (1970s), and it has recently appeared along the banks of a stream in Northlands
Park (1998). Similarly a large colony on an embankment cast of the A176 at Noak Bridge (1993)
has apparently seeded into grassland above, and a few plants were found in a triangular roadside
grassland remnant at Laindon in 1986. A colony is also known from Langdon Nature Reserve near
Dry Street (Bridleway) ponds (1993). As most of these sites are maintained either by Basildon
Council, Essex County Council or the Essex Wildlife Trust, it seems very likely that as in Cornwall
where it is spreading along managed verges, seed is being spread by cutting machines used over a
wide area. The dispersed distribution of obvious new sites would suggest that there were probably
a number of additional native sites in the Basildon area that have now been built on, and that the
plant has taken advantage of the bare ground created to establish new colonies independently on
several occasions.
Essex Naturalist (New Series) 21 (2004)
151