A specimen of hydrilla (Hydrilla verticillata (L.f.) Royle) collected
at Mystic, Connecticut in 1989 was recently discovered in the Universi
ty of Connecticut herbarium. Unnoticed previously because of its misid
entification as egeria (Egeria densa Planch.), this specimen is the fi
rst authenticated record of hydrilla in New England, and represents th
e most northern locality of the species currently known in eastern Nor
th America. A 1996 field survey verified that hydrilla continues to th
rive at the Connecticut site. Connecticut plants were positively ident
ified as hydrilla by morphological features, and by comparing the rbcL
gene sequence of Connecticut specimens with a hydrilla plant from Ind
ia. Internode lengths of Connecticut hydrilla exceeded those reported
for both dioecious and monoecious strains grown in greenhouse conditio
ns. However, leaf lengths of Connecticut hydrilla were comparable to t
hose of the dioecious strain designated as 'USA hydrilla I'. A RAPD pr
ofile of Connecticut hydrilla produced the molecular marker that repor
tedly distinguishes the dioecious strain. Cytological analysis indicat
ed that the Connecticut hydrilla plants are triploid (2n = 3x = 24). H
ydrilla in Connecticut presumably represents an introduction of dioeci
ous plants. Hydrilla grew well on both sandy and mucky substrates and
apparently overwinters in Connecticut by production of numerous, subte
rranean stem tubers.