August gardening tips
Trees, shrubs and climbers
Carry on cutting back perennials and deadhead all dying and spent flowers on annuals, roses and shrubs; not only will your garden look immeasurably tidier, but the plant will be prevented from putting energy into the seed and may be encouraged to reflower.
When deadheading roses, cut the stem down with sharp secateurs; just breaking off old flowerheads will leave the rose vulnerable to infection. It's too late to spray roses for blackspot now - once established spraying will not help. Pick off infected leaves and burn; do not put them on a compost heap where the spores will spread the disease.
Trim back lavender and rosemary after flowering without cutting too far into the old wood and summer prune wisteria by shortening wispy sideshoots to about 20cm. Soak the soil with a high potash fertiliser if your wisteria's flowering performance was a bit feeble.
Collect seed heads
Save seeds from the seed heads of hardy annuals, perennials, bulbs, rock plants, trees and shrubs. Growing plants from seeds you have collected is fantastically rewarding, but you need to be vigilant; seed heads have a nasty habit of ripening and popping whilst your back is turned. Collect when nearly ripe - just as they are turning brown. Snip them off, put them in a paper bag, label and hang somewhere cool, dark and dry.
Cuttings of perennials and bedding plants will root well at this time of year and quickly become strong enough to overwinter inside.
Train a long flexible shoot to ground level, cut a shallow sloping slit in it, dust the cut surfaces with hormone rooting powder, peg down to hold in place in soil enriched with a little potting compost and wait for it to root.
Keep hedges neat and under control for both their appearance and good relations with the neighbours!