The habitat of Lythrum hyssopifolia L. in cambridgeshire, its only surviving English locality

Abstract

Lythrum hyssopifolia, always a scarce species in the British Isles, is now confined to Cambridgeshire and to Jersey, Channel Islands. In Cambridgeshire it is restricted to an area of 10 km 2, where it occurs locally in shallow depressions in arable fields, consistently associated with Bryum klinggraeffii, Juncus bufonius, Plantago major ssp. intermedia and Polygonum persicaria. it is dependent on both winter flooding and the regular ploughing of these sites for its survival. The vegetation in which it is found is referable to the Isoeto-Nanojuncetea, largely composed of annual flowering plants and ephemeral bryophytes. Lythrum and its most frequent associates share: (1) the ability to germinate in spring; (2) the lack of long-term competitive ability; (3) a similar floral biology, being predominantly self-pollinated; and (4) potentially long-lived seeds. Two groups of bryophytes grow with Lythrum, monoecious species reproducing sexually and dioecious species reproducing vegetatively by rhizoid-tubers.