What to Do in the Vegetable Garden This August

Published on August 8th 2020
A pile of orange tomatoes
August is a glorious month to be out in the garden, especially if you grow your own food. Abundance is all around, and it's time to make the most of it!


Insect proof net over cabbages in a garden
  • If you would rather not cover your vegetables in net to keep pests off, try regular sprays of diluted garlic spray.
  • Fill spaces in the veg patch by sowing quick maturing items such as turnips or, better still, varieties that will provide tasty winter salads like , corn salad (lamb’s lettuce), rocket, and radicchio. These are not hard to grow and will provide tasty, nutritious homegrown salads in the middle of winter!
  • Trees that produce fruit with stones, rather than pips, should be trimmed now. Plums, cherries, apricots, peaches and nectarines are best pruned during the summer when they are less likely to get infected with the incurable silver leaf disease. Immediately paint any significant cuts (over 1” diam.) with Seal & Heal wound healing paint.
  • Sow seeds of autumn onion [sometimes called Japanese onion] this month for the earliest crop of next year. You’ll be able to buy onion sets next month, but seeds are cheaper!
onion plants
  • Keep picking runner beans and courgettes regularly. If you don’t, they will stop producing more. Both can be used to make excellent chutney or can be given to neighbours and friends.
  • Dig up your potatoes. Dry and store undamaged tubers in a dark, frost-free place for winter. Late main-crop and winter salad potatoes will need a little longer in the ground and may put on a lot of tuber growth in the next few weeks. First early, and most second early, varieties will be ready to lift now.
  • Harvest all marrows and cucumbers regularly. If you don’t, they will stop producing. Give excess produce away or conserve them. Even throwing them on the compost is better than leaving them on the plants.
A person holding cucumbers
  • Watch out for early blight on potatoes. Only a few sprays are effective, so it might be best to cut the tops off if your crop is infected. If you don’t, then the spores can be washed from the leaves and infect the tubers underground.
  • Plant more winter vegetables. As it’s late in the year for most, try to buy plug plants or baby plants. This is especially true for leeks, purple sprouting, beetroot and kale. Here are a few good varieties:


  • Prune out summer fruiting raspberry canes that have finished cropping.
  • Order fruit trees and bushes for autumn and winter planting.
  • Order strawberry runners for late summer and autumn planting. Don’t forget to order some for planting into grow-bags - or other containers - to force under protection for the very earliest berries.
Strawberry plants and a grow bag
  • Summer prune intensively trained fruit trees. So that's plants which are espalier, cordon, fan and step-over trained.


  • Turn your compost heap over and water it thoroughly if it appears dry.
  • The decomposition process can be accelerated by mixing in some compost activator. Cover the top with an old carpet to keep in the heat generated by all the useful micro-organisms that will be breaking your garden prunings down to form good garden compost to dig in the borders in autumn.
  • Get some more compost tips here:
  • Compost heaps can get too dry, so check and soak them if necessary. If they are too dry, the decomposition slows down.
Composting bins in a garden

Soils, mulching, weed control, etc

  • Creeping thistles, nettles and brambles can be controlled with SBK Brushwood Killer now.
  • It’s not too late to mulch your beds and borders to control weeds. Use chipped bark, composted green waste, mushroom compost or decorative gravel.

Greenhouse and protected crops

  • Remove the leading shoot when your greenhouse tomatoes have set five trusses of fruit. This will encourage all the fruit to ripen before late autumn.
  • Regular feeding with a tomato feed will help this, and also makes the fruit tastier!
tomatoes on the vine
  • Check greenhouses for whitefly. They are a little bigger than midges and will fly up in clouds if you disturb them. Yellow sticky pads will trap lots of them but don’t use these if you have introduced or are encouraging natural predators. S B Invigorator sprays have a physical (not chemical) mode of action, but you will need to spray very thoroughly. If you have to use chemicals, Provado Ultimate Bug Killer is currently the best available.
  • Powdery mildew can be a problem on some cucumbers so remove leaves as soon as you see the typical white powdery coating. Ensure that the roots are kept moist and try controlling with a solution of 50:50 milk and water.
  • Watch out for red spider mites on greenhouse plants. Symptoms include pale speckles appearing on the shoot tips, webbing of the same areas and tiny insects just visible to the naked eye. Introduce predatory mites as soon as you see this troublesome pest.
Red Spider Mite on cucumber leaf
  • Pot up a few roots of garden mint. Kept inside you will get fresh mint well into winter.
  • This is a good time to control vine weevil using a nematode biological predator. It’s simple to water onto pots and borders but make certain that they are wet first and agitate the solution as you apply it.
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