For the budding botanist looking for unusual stuff, and who doesn't want to drive to a nature reserve to find rarities, local back alleyways can throw up some interesting surprises.
Greater Celandine (Chelidonium majus) - tends to be found as isolated individuals here and there, but there are a large number of plants in the alley off the north side of Northumberland Park (and near the clubhouse at Barnehurst golf course)
Lemon Balm (Melissa officinalis) is garden escape that is found, most often as a single plant, reasonably frequently in this part of the Borough
Fortunately, Japanese Knotweed isn't too prevalent here.
Caper Spurge (Euphorbia lathyrus), a biennial probably native in the south and a garden escape elsewhere. Uncommon.
This Ribes turned out to be a Redcurrant, flanked by Blackcurrants, no doubt planted.
The Hop (Humulus lupulus) is often found in back alleys in the North Heath to Bexleyheath area, and along the Bexleyheath railway line.
Spotted Medick (Medicago arabica) is frequent in Barnehurst verges and other local areas where grass is kept short, but is not usually found in alleyways.
A very strongly-marked White Clover is an attractive sight.
The Corsican Hellebore (Helleborus argutifolius) self-seeds freely in my sandy Barnehurst garden, but this is the first garden 'escapee' I've found.
It will be noted that a reasonable knowledge of garden flora is an advantage in surveying such habitats!