A couple of month ago I dug up some alpine plants and inadvertantly disturbed a fairly large population of solidary bees which had nested in the soil. The latter covers a large area and is approximatley 30 ft x 2 ft and is right in front of my front window so naturally I do want a strip of bare soil on show, but on the other hand I do not want any harm to come to the bees. Is there a time of the year when I could plant some perennials, e.g. wall flowers, but cause only limited disturbance to the bee population?