August Gardening Calendar

One of the hottest months of the year, August is time for late flowering perennials, while colourful annuals have many weeks left to show and weeds stop being such a bother at last

Flowers and shrubs

  • Water plants in pots and baskets, and don't forget to regularly soak camellias so they don't dry out, as drought might cause their buds to drop next spring
  • Take cuttings from tender perennials and bedding plants, choosing non-flowering shoots
  • Collect seed from any flowers that you'd like to propagate, including aquilegia, polemonium, foxgloves and ornamental grasses
  • Deadhead roses, unless you want them to form autumn hips. Identify problems and pick off diseased leaves - dispose of any leaves infected by rose blackspot or rose rust in your dustbin and not on the compost heap
  • Deadhead: pelargoniums and other summer bedding plants; dahlias to encourage them to flower again; and lady's mantle or other hardy annuals if you don't want them again before they self-seed prolifically. Tidy up fading perennials - make compost with all the trimmings and break up the layers of grass cuttings
  • Prune: philadelphus, weigela and other early summer-flowering shrubs; summer wisteria side shoots back to 20cms; pyracantha and train shoots to supports
  • Clear bedding that has passed its best and plant out forget-me-nots and wallflowers for a gorgeous blue and orange display
  • If you haven't already harvested your lavender, trim it immediately after flowering to maintain its shape but avoid cutting back into old wood. Take lavender cuttings by pulling off side shoots and inserting them in trays of gritty compost
  • Hoe weeds regularly to prevent seedlings establishing
  • Propagate lily bulbs by taking off a few outer scales and putting them in bags of compost or pot up bulbils formed on their stems
  • Sow hardy annuals, like poached egg plant, for early flowers next year
  • Tie tall chrysanthemums to supports
  • Plant autumn crocuses, sternbergia, colchicums, hardy cyclamen and nerines

Fruit and vegetables

  • Check sweetcorn to see if it's ripe and ready to pick - it will be when the tassels start to go brown
  • Pick beans and water crops regularly
  • Pick plums as they ripen and freeze any surplus immediately
  • Pile up the earth around trench varieties of celery for whiter stems
  • Prune blackcurrants after fruiting, removing about a quarter of the oldest stems
  • Transplant well-rooted strawberry runners
  • Ease onions from the soil with a fork to prepare them for harvesting and lift once their tops die down
  • Finish pruning trained forms of apple trees like cordons, espaliers and fans
  • Water crops regularly, especially during hot weather
  • Lift marrows into the sunshine and rest them on bricks to ripen. Harvest some young and leave some to fully ripen for storage and winter use
  • Identify plants showing symptoms of potato blight, and immediately remove affected leaves and stems
  • Pinch out the tops of outdoor tomatoes, as further flowers are unlikely to produce ripe fruits
  • Thin out heavy plum crops to prevent branches from snapping
  • Use netting to protect blackberries and autumn-fruiting raspberries from birds
  • Trim leaves from strawberries that have finished fruiting and plant out rooted strawberry runners into new flower beds. Pot some up to bring into the greenhouse later in winter for early fruits
  • Pick early varieties of apple as they ripen including Discovery, Laxton's Epicure and George Cave
  • Hang wasp traps and place grease bands to catch wingless winter moths on fruit trees
  • Pick fresh herbs to freeze in ice cubes for winter use
  • Vegetables to sow now include beetroot for leaves, lettuces, beetroot, coriander, radishes, spring cabbage, spring greens, spring onions, turnips for their green tops, spinach, swede, Swiss chard, winter lettuce and winter spinach

In the greenhouse

  • Damp down the greenhouse floor every morning on hot days to increase humidity and shade delicate plants to avoid sun scorch or really hot days - open vents every day but close them at night if the weather turns cold
  • Water plants and crops in pots and grow bags every morning, and again at night if necessary. Add liquid feed to at least one watering a week to keep plants growing strongly
  • Be vigilant for pests like red spider mite and take action against any right away - deal with vine weevil by watering pots with a solution of biological control nematode
  • Sow parsley in modular trays, and winter lettuce and chives in pots for winter and spring crops. Cut down chive leaves to stimulate new growth
  • Feed tomatoes in grow bags and pots with a liquid high-potash fertiliser
  • Harvest greenhouse cucumbers regularly to promote further flower development
  • Plant nerines, lachenalia and veltheimia bulbs in pots, as well as freesias, and sow pots of hardy annuals for early spring blooms
  • Take cuttings from verbena, begonias, Cape primroses and African violets
  • Stop watering pots of gloxinia and tuberous begonias to let them die down completely before storing tubers in dry compost for winter
  • Buy prepared hyacinth bulbs and plant as soon as possible so you'll get flowers for Christmas
  • Water indoor cyclamen after their summer rest to encourage new growth and plant pots of Paper White narcissus for indoor displays

Lawn and trees

  • Deal with problem lawn weeds by either digging them out or applying a weed killer suitable for lawns
  • Continue to mow lawns every week
  • Prune pleached trees
  • Remove suckers growing around or on stems of roses, trees and shrubs
  • Trim box topiary, conifer hedges and evergreen hedges such as privet, cutting their tops back to the desired height. Cut laurel hedging with secateurs so as not to damage remaining leaves

General maintenance

  • Trap earwigs among dahlias with upside-down pots stuffed with straw or newspaper and balanced on canes - kill any you find
  • Remember to water your garden, particularly containers, pots and new plants, when necessary but make sure roots get properly soaked rather than just wetting the surface soil. Preferably use grey recycled water or stored rainwater
  • If you're going on holiday for more than a week, it might be worth setting up an automatic watering system with a drip nozzle for potted plants
  • Keep ponds and water features topped up and remove any pond weed with a small net

Plan ahead

  • Order spring-flowering bulbs to plant this autumn, such as tulips, narcissus, fritillaries, alliums, iris and crocus
  • Buy pansies and other winter bedding plug plants to grow on under cover
  • Order sweet pea seeds for autumn sowing in pots
  • Order garlic bulbs and onion sets for autumn planting

Little green fingers

  • Once your foxgloves are over their best and the seeds are ready to be harvested, cut the flowers and lay them over a large tray. Children can shake out the seeds and plant some straight away in small pots of compost. But make sure your kids don't try and eat them.
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