What to do in the garden in August

children in a garden with a watering can and a hose
With the kids on holiday, enjoy the garden as a family!
Image: varuna

The last official month of summer is the perfect time to enjoy your garden while it’s still at its best. Children are on school holiday, lawns are in full use, and there’s plenty of delicious fruit and veg to fill your dinner plate. If you’re planning a holiday in August, be sure to read our blog post on watering for tips while you’re away.

For this month's planting advice, have a look at our what to sow and grow in August page. In the meantime, here’s a list of jobs to keep on top of:

Timely Tips

closeup of orange begonias in hanging baskets
Don't forget your hanging baskets during the hot weather
Image: Jacqui Martin

You might be thinking about having a holiday this month, but August isn’t the time to take your eye off the ball in the garden. Here are some of the main jobs:

  1. Top up ponds and bird baths regularly.

  2. Water fruit and veg plants daily.

  3. Prune all summer flowering shrubs once the blooms are finished.

  4. Keep on top of weeds as they compete with your crops for nutrients and water.

In the flower garden

Dahlia 'Dalina Salinas' (The Windmill Dahlia) from Thompson & Morgan
Ensure top-heavy dahlias are staked to prevent damage
Image: Dahlia 'Dalina Salinas' (The Windmill Dahlia) from Thompson & Morgan
  • Water camellias and rhododendrons thoroughly this month to make sure that next year's buds develop well.

  • • Keep patio container plants well watered and feed with a liquid fertiliser every fortnight.

  • Stake tall or top-heavy dahlias and lilies to prevent wind and rain damage.

  • Dead-head bedding plants and perennials to encourage them to flower into the autumn and stop them self-seeding.

  • Cut back faded perennials to keep borders tidy.

  • Dead-head lilies for a better flower display next year.

  • • As penstemon flowers fade, cut them back to just above a leaf to encourage more flowers.

  • Cut back herbs now to encourage a new flush of tasty leaves you can harvest before the frost.

  • Prune wisteria after flowering by removing all the whippy side-shoots from the main branch framework to about 20cm from their base (about five leaves from the main stem).

  • Trim any lavender plants after they've finished flowering to keep them compact.

  • Collect ripened seed and store for next year. Leaving some seed heads in place can be attractive and allows the plant to self-seed in the surrounding soil.

  • Mow wildflower meadows now to help scatter the seeds.

  • • Take cuttings of your favourite tender perennials such as pelargoniums and fuchsia to propagate them for next year.

  • Finish dividing clumps of bearded Iris now so they have time to form roots and flower buds for next year before the cold weather arrives.

  • Prune climbing roses and rambling roses once they've finished flowering (unless they’re repeat-flowerers in which case leave them).

  • • Spray ground elder (and other perennial weeds) with a glyphosate-based weedkiller as the plant has lots of leaf surface area with which to absorb it.

  • Look out for symptoms of ‘clematis wilt’ including black discolouration on the leaves and stems of your clematis. Cut out any infected plant material and dispose of it in your household waste.

In the vegetable garden

Potato ‘Kestrel’ from Thompson & Morgan
Perfect for salads, keep harvesting your second early potatoes
Image: Potato 'Kestrel' from Thompson & Morgan

The vegetable garden comes into its own in August, with plenty of delicious home grown produce to harvest. Here are some tasks to keep you busy this month:

  • • Water sweetcorn plants regularly and feed with tomato food to get the best cobs.

  • • Apply a high-potash fertiliser such as tomato food once fruits start to form on pepper, cucumber and aubergine plants.

  • Continue to feed tomato plants with a tomato fertiliser and remove lower leaves to help with air circulation and prevent disease.

  • • Pinch out the top of tomato plants to concentrate the growth into the fruit that has already formed. Aim to leave 5 or 6 trusses of fruit per plant.

  • Cut back herbs to encourage a new flush of tasty leaves that you can harvest before the frost. Dry or freeze excess herbs to use in the kitchen later on.

  • Thin parsley to help it establish a good root system before winter. There should be 25cm between each plant.

  • Pinch out the tips of your runner bean plants once they reach the top of their support. This encourages side-shooting and more beans at a manageable height for picking.

  • If you're growing aubergines pinch out the growing tip once they have 5 or 6 fruits. Pick fruits while they’re young and shiny.

  • • Limit the fruits on a squash plant to about three, but make sure these fruits are established before pinching out the surplus.

  • Spring-sown carrots and beetroot will be ready to harvest now although they can be left in the ground to keep growing.

  • Continue to harvest second early potatoes now - perfect for salads!

  • Start harvesting your maincrop potatoes as the leaves yellow and die back. Store your potatoes in hessian sacks which exclude light but allow ventilation.

  • • Sweetcorn is ready to harvest when you can pop a corn with your thumbnail and the juices are milky.

  • Lift and dry onions, shallots and garlic once the foliage has flopped over and yellowed. Store them in onion bags to prevent mould developing.

  • Harvest French and runner beans little and often to prevent them from setting seed.

  • Pick runner beans regularly to prevent them becoming stringy and to make room for developing pods. Leaving mature pods to set seed can prevent further flowers developing and reduce your crop.

  • • Keep harvesting courgettes before they become too big!

  • Take cuttings of herbs such as rosemary, sage or mint now to bulk up supplies. Put cuttings in moist, well-drained potting compost (one part grit to one part compost) and place in a cold frame.

  • • Established clumps of chives can be divided now.

  • On a sunny day, collect seeds of herbs such as dill, fennel, caraway and chervil and dry in a warm spot out of direct sunlight. Chervil must be sown immediately.

  • Keep an eye out for potato and tomato blight and remove and destroy any affected plants immediately to prevent its spread. Read our 'How to stop blight' guide for more information.

  • Check for cabbage white butterfly eggs under brassica leaves and squash any that you find. Alternatively use nematodes to kill the caterpillars.

  • • Clear away any diseased and spent foliage around your veg plants to discourage pests and diseases spreading.

In the fruit garden

Homemade bird scarer made from unwanted CDs tied with string around crops
Try this handy DIY trick to keep birds away from your crops
Image: chrisatpps

Here are the main jobs to do in your fruit garden this month:

  • If you have plants fruiting in containers, make sure you give them a high potash liquid feed to keep them healthy and productive.

  • Remember to feed your lemon tree (and other citrus fruit trees) throughout summer with a special citrus fertiliser.

  • • Plant out any rooted runners of strawberries for a good crop next year.

  • Keep birds and squirrels off your berries with netting or old net curtains.

  • Protect your crops with a bird scarer made from CDs tied to strings.

  • Harvest your fruit trees - cherries, plums, peaches, nectarines and apricots should all be ripe now! Early varieties of apple trees will be ready towards the end of the month.

  • If you have a glut of autumn raspberries, blackberries or loganberries, freeze them on trays for a couple of hours and then bag them up to use over winter.

  • Tidy up strawberry plants and remove any old straw from around the plants to improve ventilation and reduce the risk of pests and diseases.

  • Prune the fruited stems of your blackcurrant bushes after harvesting.

  • • Cut back the fruited canes of your summer raspberries, leaving the new green canes for next year's crop. Tie in next year's raspberry canes to support wires or fencing.

In the greenhouse

person watering seedlings in a greenhouse
Check plants daily for dry soil
Image: Arturs Budkevics

Here are the main jobs to do in your greenhouse this month:

  • Check plants daily and water them if the soil is dry.

  • Damp down your greenhouse on hot days to increase humidity and deter red spider mites.

  • Open vents and doors on warm days.

  • Use blinds or apply shade paint to prevent the greenhouse from over-heating in sunny weather.

  • • Try hanging sticky traps to catch flying pests and help determine which pest control is needed.

  • Tidy up fallen leaves and flowers to discourage disease.

Looking after your lawn

closeup of an ant on some grass
Keep your eye out for ant nests
Image: Shutterstock

Here’s how to look after your grass this month:

  • Don't worry if your lawn is looking brown, the autumn rains will soon make it green again.

  • Don't feed your lawn with a high-nitrogen fertiliser now as this will encourage lots of lush new growth which is easily damaged by autumn weather.

  • Lawn growth slows down in late summer so raise the cutting height of your lawn mower to help the grass cope.

  • • If you're planning on laying a new lawn this autumn, prepare the area now to give it time to settle.

  • • Recut any lawn edges. Install lawn edging to make future maintenance easier.

  • If your lawn is infested by ants, brush out the nests on a dry day. Always brush them away before mowing.

Other jobs about the garden

man cutting hedge with an electric strimmer
Give your hedges a final trim
Image: adriaticfoto

Here are some other jobs to keep on top of during August:

  • Give hedges a final trim before they stop growing.

  • Water plants thoroughly when needed instead of every day. Thorough watering supports plants for up to 14 days, while merely wetting the surface wastes water, encourages weeds and can lead to surface rooting making the plants more vulnerable.

  • Use water butts as much as you can to water your plants.

  • Recycle your water - collect washing up water in a bucket outside for watering beds and lawns.

  • Turn the compost in your compost bins every month to keep it well aerated and to speed up decomposition.

  • • Scoop floating weed and algae from ponds.

  • Remove rampant bulrushes or irises from your pond before they go to seed and make the problem worse.

  • • Now is a good time of year to treat lawn chafers and leatherjackets with nematodes.

  • Keep an eye out for white powdery mildew on plants. If possible, remove the affected parts and spray with a fungicide to prevent further spread.

  • Look for aphids on the underside of leaves - rub them off by hand or spray with an insecticide to prevent them multiplying. Alternatively try using a natural pest control such as Lacewing larvae.

  • Keep an eye out for scarlet lily beetles on your lilies - remove and crush any you see. Also check for the sticky brown larvae on the underside of leaves.

  • If your plants are wilting, check for vine weevils by tipping your plants out of their pots and looking for 'C' shaped creamy maggots amongst the roots. Treat with nematodes if vine weevils are spotted.

  • • Prevent slugs attacking your young plants by using slug control.

  • Use boiling water as a weed killer on your paved areas. Weeds wilt and die within a few days.

From your armchair

young girl taking photos in a garden
Take plenty of photos while your garden's in full bloom
Image: Teresa Kasprzycka

August is a great time to enjoy your garden, but also a good moment to cast a critical eye over your domain and decide what you’d like to change for next year. Here are some tips:

  • Make rough sketches of your flower borders and vegetable plot to help plan for next year.

  • Take lots of photos of your garden if you want to rearrange things over the winter - it's much easier to do this if you have a reference point.

  • • Think about which bulbs you would like for next spring - now’s the time to order ready for autumn planting.

  • Order your perennial plants online now ready for autumn delivery.


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