Month by month
Garden jobs for August: what to do in the garden
August often feels like a continuation of July, with warm days and dry soil in the south and east, and heavier showers in the north and west. Nights start to lengthen noticeably by the end of the month, and heavy dews in the morning are a reminder that autumn isn’t far off. It is a month of harvesting, tidying and planning rather than big projects. If you’re going away, sort out watering before you leave: group pots together in light shade, stand them in trays of water, or ask a neighbour to help in exchange for a share of the crops.
Flowers and borders
Once lavender has finished flowering, trim it into a neat mound, cutting off the flower stalks plus a couple of centimetres of leafy growth. Keep the cuts in green, leafy stems; lavender rarely regrows from bare, woody wood, so avoid cutting into the old framework. Carry on deadheading dahlias, cosmos and penstemons to keep them flowering until the first frosts. It is also a good month to root semi-ripe cuttings of lavender, rosemary and hebe; our guide to taking cuttings shows how.
Leave the seed heads on plants such as rudbeckia and echinacea if you want winter structure and food for finches, but collect a few seeds from annuals you’d like to grow again. Pick seed heads on a dry day, put them in a paper bag, and let them finish drying indoors before storing them in labelled envelopes somewhere cool. Cuttings of tender perennials such as salvias, pelargoniums and penstemons root quickly now: take non-flowering shoot tips about 8cm long, trim below a leaf joint and push them round the edge of a pot of gritty compost.
August is also the time to order spring bulbs while the full range is in stock. Daffodils go in from September, but tulips are best planted in November, so there is no rush to get them in the ground yet.
Vegetables
Harvest onions and garlic once the leaves have flopped and yellowed, and leave them to dry in the sun or a well-ventilated shed for a couple of weeks before storing. Sweetcorn is ready when the tassels at the top of the cob have turned brown and a pierced kernel gives a milky liquid. Keep picking beans, courgettes and tomatoes.
Sow spring cabbages, oriental greens such as pak choi and mizuna, winter salad leaves and overwintering spinach. In northern gardens, sow early in the month so plants establish before the light fades. Clear finished crops promptly and either sow green manure such as field beans or mustard, or cover the soil with compost to protect it over winter.
Fruit
August is the key month for summer pruning in most of the UK. Prune trained apples and pears if you didn’t in July, and cut the long whippy shoots on wisteria back to about five or six leaves from the main framework. This keeps the plant manageable and encourages flower buds to form for next spring. Plum and cherry trees should be pruned in summer rather than winter, after fruiting, to reduce the risk of silver leaf disease. Prop up branches heavily laden with fruit, and pick up fallen fruit to deter wasps.
Lawns
Avoid feeding the lawn in dry spells. If you’re planning to sow a new lawn or patch bare areas, prepare the soil now so you’re ready to sow in early September, when warm soil and returning rain give grass seed the best start.
Wildlife
Ponds can get low in August, so keep them topped up with rainwater. Hedgehogs are busy building up fat reserves; a shallow dish of fresh water and a gap of about 13cm in the bottom of a fence will help them move between gardens. Delay cutting hedges if birds may still be feeding late broods, and check carefully before you trim.
Indoors and under cover
Remove the lower leaves of tomato plants as they yellow to improve airflow, and stop cordon tomatoes by pinching out the growing tip once they have four or five trusses outdoors or six to seven under glass. Keep greenhouse vents open on warm nights. Pot on rooted cuttings and start thinking about where tender plants will spend the winter.
Plants looking good this month
Late summer colour comes from crocosmia, agapanthus, sunflowers, Japanese anemones just beginning to open and the long-flowering hardy fuchsia, which keeps going well into autumn. Hydrangeas are at their best too, with mophead flowers slowly shifting colour as they age.
Looking back or ahead? See July jobs or move on to September jobs.
From the plant finder
In flower in August
Good time to plant
Due for pruning
Grow your own in August
Sow now
Plant out
Ready to harvest
Problems to watch for in August
Spotted something else? Diagnose it by symptom.