Urban flora fascinates me. One of the reasons is that the exceptional floristic diversity found in urban habitats challenges my ideas about wildlife and conservation. We tend to think of urban development as intrinsically adverse to biodiversity, however, re-colonisation can be quick and novel habitats can be rich and surprisingly biodiverse.
This positive aspect needs of course to be weighed up against irreversible loss of some habitats such as nutrient poor mires that can disappear and are never replaced.
But I also enjoy urban floras because so many unexpected plants turn up! and because it transforms my weekly trips to the supermarket into genuine botanical expeditions. Above and below are pictures of Filago vulgaris, the common cudweed, in a waste ground in (SK337889) Walkley, Sheffield, UK, near home. I had spotted the hundreds of tiny rosettes early this spring but couldn’t work out whether it would turn out to be a Filago or Gnaphalium uliginosum, the marsh cudweed.
Last August, I was fortunate to be shown several ponds near Catcliffe and Treeton, East of Sheffield, UK, by Bob Croxton, form Sorby Natural History Society. The area is full of history and is a fascinating example of nature recovering following industrialisation.For instance, one of the ponds visited was formed in a lost piece of land amongst spoil heaps and three railway line! At this site Persicaria maculata and Nymphoides peltata were in full bloom (see picture) and two Potamogeton species were observed, now confirmed as P. pectinatus and P. pusillus. However only one shore was prospected and other nice aquatic plants are likely to be present in the rest of the pond.
On the whole, too many of the water bodies in the area were absolutely dominated by Elodea nuttallii, an invasive species that colonised the UK from the 1970s. It’s phenomenal spread in Britain and Ireland is summarised in a paper by Simpson that can be read from the BSBI archives. It remains unclear whether this spread has caused arm to aquatic biodiversity or whether it was simply facilitated by degraded habitats.