Bladderworts (Utricularia) in Essex
Ken Adams 63 Wroths Path, Baldwins Hill, Loughton, Essex IG10 1SH
Despite their spectacular nature, Bladderworts in Essex have been poorly recorded and
the taxa confused. Stan Jermyn (1974) put them all down as 'Greater Bladderwort'
Utricularia vulgaris, despite the fact that even in Gibson's day (1860s) the existence of
Utricularia australis (neglecta) had been recognized, because he had not got round to
sorting out the two in Essex. In the past the stumbling block has apparently been not
finding the flowers to confirm which species is involved.
The stronghold of the Essex Bladderworts is undoubtedly Epping Forest. The so-called
Common Bladderwort U. australis, characteristic of acidic waters, appears to be the
only species involved, and despite the claim that it seldom flowers, it does do so most
years - mainly during August when most people are away on holiday! The fisherman
make life hell for it in Wake Valley Pond, but it can usually be found with a few flowers
in mid-August in either Wake Valley Pond, the Bomb Crater and/or the two Lesser
Wake Valley ponds. It also quite often flowers in the small Oak Pond on High Beach.
Over the winter of 2001/2002 Upper Wake Valley Pond was completely scoured down
to the gravel. This was done primarily in an attempt to exterminate the various aquatic
aliens present, in particular Crassula helmsii, which had formed a 'wet blanket' across
the eastern half of the pond, and Hydrocotyle ranunculoides, which despite efforts to
weed it out had entwined its brittle stems into an extensive Typha bed around the island.
I had hoped that the pristine gravel bottom would attract or stimulate the growth of
Stoneworts, but it rapidly became coated with a thick layer of autumn leaves. By 2003 a
spectacular colonisation of the eastern margin by Bristle Scirpus Isolepis setacea had
occurred, with several hundred plants eventually in flower. The seed had almost cer-
tainly been washed down from the bank above, onto the pristine clay surface, from a
former colony on the bank some years previously. In the shallow waters Floating Scirpus
Eleogiton fluitans also had its day, free from competition it formed extensive floating
rafts and eventually flowered in profusion. On the down side, Equistem fluviatile, a rare
species in Essex, and Hottonia palustris (Water Violet) seem to have been extermi-
nated, and an even greater rarity Apium inundatum, which is heavily out competed by
Crassula helmsii whenever the two grow together, has yet to return. Quite unexpectedly
however, during the summer of 2003, Utricularia australis, some fragments of which
appear to have been introduced to the cleaned out pond, suddenly began to grow explo-
sively, exploiting a vast population of water fleas, and forming a dense blanket of its
delicate pale greenish yellow zig-zag shoots, sporting millions of bladders. By mid-
August they had begun to flower, and by the first week of September there were half a
dozen or so flowers per square meter, and many thousands of them across the pond as a
whole. Then, all of a sudden, by the end of the third week of September, all the plants
were dead and had begun to decay into an unrecognisable mess.
Essex Field Club Newsletter No. 45, September 2004 17