If so, take a look at the bees foraging at its flowers. I did this in my garden just over the border in Suffolk and discovered a Nationally Scarce bee Macropis europaea. In the wild it is very much associated with the wild Yellow Loosestrife, which is thin on the ground in my part of Suffolk and even rarer in Essex. Nevertheless, this female had found my one square metre of Dotted Loosestrife from a population quite unknown to me. My nearest record of the bee in Suffolk is tens of miles away. In Essex there are only two post-1990 locations, both right in the south of the county.
If you look at the females' hind legs they are quite distinctive, with whitish hairs covering the lower part (tibia) and a large brush of black hairs on the first foot segment below that. The male is one of only a few bees with bold yellow coloration on its face. See http://www.bwars.com/index.php?q=bee/melittidae/macropis-europaea 
for photos of this bee and further information about its ecology.