Wilden Marsh and Meadows is the richest and most diverse wetland habitat in Worcestershire. Here are a few of the locally scarce flora that can be found growing on the valley floor of this Reserve.
The river valley in this area was deeply excavated into the Triassic sandstone country-rock during cold stages of the Pleistocene, which also left valley-floor deposits of sands and gravels. During the Flandrian, superficial deposits of fen peat and alluvial clayey silts accumulated to a depth of about 3 metres, accounting for the present nearly flat topography. In the last century the River Stour was canalised to its present course in the Lower Stour Valley at Wilden, from the original course closer to the line of the canal.
Most of the reserve has circum-neutral soils which are damp or wet throughout the year, including alluvial and gleyed soils developed on clay-silts and humic soils overlying fen peat. In small areas with underlying sandstone bedrock the soils tend to be more acidic and drainage is freer.
A high water-table was responsible for development of fen peat and the continuing existence of fen vegetation on the reserve. Flood alleviation work carried out by The Severn Trent Water Authority during 1978 and 1979 excavated the channel of the river by up to 2 metres south of Platts Wharf. Piezometer records show that this has caused a significant drop in the level of the water-table within the marsh, especially at the southernmost part of the reserve. In 2010 two rock weirs were constructed to raise the water levels by 2 metres at each weir (close to Pratts wharf and also at WWT southern end).