If you have a greenhouse or a porch where you can over-winter plants, take cuttings now of all those half-hardy plants that either limp along during the winter or that are killed by frost. These include tender geraniums (correctly known as Pelargonium), osteospermum, fuchsia, argyranthemum or Paris daisy, verbena, felicia.
September is traditionally the month for sowing grass seed (but you can do it into October if you live in a mild area). Choose a grade (numbered from 1 to 4) of grass seed to suit your purposes. Grade 1 is for fine, bowling-green type swards, and should only be considered by lawn-maniacs (who won't be reading this, as they'll be out manicuring), grades 2 and 3 are harder-wearing. Choose number 3 if you have children or pets. Grade 4 is for difficult areas such as shade and dry slopes. Allow about 30 to 45 grammes of seed to each square metre. Dig the soil, and be sure to remove any large stones and roots of perennial weeds. Leave the soil to settle a few days, then consolidate it by walking all over it on your heels. Rake the surface smooth and scatter half the seed evenly across the patch one way, scatter the other half at right angles. Rake in lightly.