Posted: 13/10/2012 at 23:17
I wouldn't assume that the topsoil will already be poor, although sandy soils will be less so. Loamy and clay topsoil will be richer in minerals and nutrients.
Much of the topsoil should be removed where you intend growing wildflowers. (On a larger scale, stack any turf upside-down in a corner somewhere to rot and provide useful loam for the garden). Dig over the wildfllower plot to mix the remaining topsoil with subsoil (as this provides a poorer growing medium). Try to establish which type of soil you have, and sow wildflowers that grow naturally in those specific conditions for the best results. Contact your local councils' environmental or ecology sections for local information.....or a nearby horticultural or agricultural college.