August is the end of my gardening year and I tend to adopt a very French attitude to it - it is a holiday period. The weather should be hot and friends and family come to stay (I accept this year is very different), so garden tasks are at a minimum and are composed of essentials only - so:
Water, weed and feed. Keep the irrigation going. Plants are setting seed like crazy now and these will disperse themselves around the garden. Remove weeds and unwanted seedlings while they are tiny; it makes life much easier in the long run. Meanwhile pots of plants will be very hungry. The nutrients supplied in the compost you used to fill the pots way back in May will have long been used up and you need to be supplementing water with feed on a regular basis. Use a balanced plant food that supplies nitrogen, potassium and phosphates (shown as NPK on the label). This provides food for the leaves, flowers and seeds and for the roots.
Collect seeds from seed heads such as nigella, poppies, echinacea, verbena and anything else you like the look of. Choose a hot, dry day and carefully shake the seeds into a paper bag. Tip them out onto a table top and remove and plant detritus and then label and store them in paper envelopes. They keep best in cool conditions, such as in a sealed container in the fridge - or do what nature does and distribute them where you want them to flower in future. I tend to do a bit of both.
Cut back dead plant material where you do not want to keep it because of its appearance or because it is useful food for the birds. Add it to the compost heap - making sure you do not include horrible persistent weeds such as convolvulus or couch grass. It is also important to clear away early season foliage where it might obscure late summer and autumn bulbs and corms - such as, for example, Cyclamen hederifolium, autumn crocuses or Stenbergias.
Tiny cyclamen hederifolium flowers usually start appearing in our garden during August. If I have not cut back the foliage of bigger plants such as aquilegia (seen here ) then it can drown the flowers and we never get to appreciate them
Harvest fruit such as blackberries and plums along with vegetables. Continue to pick French beans - the more you pick them the longer you will keep them fruiting. You can also allow them to run to seed and store the dried beans (as haricot beans) for winter use. If you haven't done it sow winter greens such as chard and cavalo nero. There are also good autumn salad mixes which can be sown now along with repeat sowings of rocket, radishes and beetroot. Pick tomatoes and either use them fresh or turn them into a coulis and freeze or bottle it.
August sees the bulk of our blackberry glut. We grow a seedless variety called Oregon Thornless which produces enormous fruit. We freeze them and eat them for breakfast all year round. Once this years fruit has been picked you can cut out the stem on which they grew. Next year's fruit will grow on this year's new stems.
Finally, as you lie on your sunbed in the August warmth (!) leaf through catalogues choosing spring bulbs to order over the coming weeks.