Dahlia 'Vulcan'Sowing and planting

Towards the end of August sow hardy annuals directly into borders. They will overwinter and flower next summer.

Cutting back, pruning and dividing

Cutting back the foliage and stems of herbaceous plants that have already died back (e.g. Dicentra) is starting to be a priority.

Don't neglect hanging baskets - deadheading, watering and feeding will help them last through until autumn.

Deadhead plants such as Dahlia, roses and Penstemon and bedding to prolong the display colour well into early autumn.

Don't cut off the flowerheads of ornamental grasses. These will provide winter interest.

Hardy geraniums can be cut back a little to remove tired leaves and encourage a new flush of growth.

Prune climbing and rambling roses that do not repeat flower or produce attractive hips, once the flowers have finished.


Pinks and carnations can be propagated by layering. Propagate irises by dividing the rhizomes if not done last month.

Take cuttings of tender perennials such as Pelargonium and Osteospermum, as soon as possible. A greenhouse, cool conservatory or a light windowsill are ideal to bring them on until they are established.

Rock garden plants, such as HelianthemumAubrieta and Dianthus can be propagated from cuttings at this time of year.

General maintenance

Feed containers, and even tired border perennials, with a liquid tomato food each week to encourage them to bloom into the early autumn.

Keep picking flowers from the cutting garden to encourage more flower buds to form and open.

Alpines that have developed bare patches of die-back, or have become weedy, can be tidied up by in-filling the patches with gritty compost. This will encourage new growth as well as improving their appearance.

Most perennial weeds are best dealt with when in active growth, if necessary applying a weedkiller.

Planning ahead

Collect and store seed of hardy annuals and perennials for sowing later in the autumn. Good plants to try include CalendulaNigellaCerinthePapaverAquilegia and hardy Geranium.

Buy or order spring-flowering bulbs. Some bulbs can be planted now, such as Colchicum, daffodils and Madonna lilies (L. candidum).

Pest and disease watch

Inspect chrysanthemums for the first signs of white rust and take immediate action.

Remove and destroy any Nicotiana showing signs of downy mildew. This shows up as yellowish blotches on the upper surface of the leaves.

Powdery mildew can be prevalent at this time of the year. Treat with an approved chemical at the manufacturer's rates.

Apply nematodes to control vine weevil grubs, in pots or the ground.

Earwigs can make Dahlia blooms ragged. Set traps to reduce damage.

Don't be worried by bright green, heavily-armoured looking insects on your plants - these are harmless shieldbugs which do not require control.

Distortion on Phlox could indicate the presence of phlox eelworm.

Discoloured leaves on herbaceous plants such as ChrysanthemumAnemone and Penstemon may be leaf and bud eelworm.


Removing blanket weed from a pondKeep an eye on aquatic and marginal plants, removing faded flowers and yellow leaves, and cutting back where necessary.

Top up water where necessary in ponds and water features. Aerate the water in hot sticky weather by leaving fountains on overnight.

Continue to remove blanket weed and duckweed using a net or rake.


Shallow water features or those with water washing over cobbles can become green very quickly in summer weather. Algicides may need applying more frequently than in normal ponds.

Clearing out fallen leaves and debris regularly will help to keep down algal growth, as there will be fewer nutrients available from rotting organic matter. Barley straw pads or extract may also be beneficial.


shed maintenanceTake advantage of the dry weather by painting fences, sheds and other wooden features with a preservative. Check that any products used are within their use-by date, and still legal. Many of the old oil-based products such as creosote are no longer approved for domestic use.

Clean up patios and hard surfaces to get rid of moss and algae. Doing this job now will prevent them becoming slippery during the winter.

Replace broken glass panes in greenhouses and fix leaking shed roofs before the autumn rains. Greenhouse guttering can also be checked to ensure it is not blocked with debris.

Greenhouse, conservatory & houseplants


damping down in the greenhouseWater houseplants freely when they are in growth.

Feed plants when necessary, usually once every one to two weeks with a liquid feed.

Start plants for Christmas

  • Cyclamen that have been resting over the summer can be started back into growth for winter blooms. Watering and careful replacement of the top layer of compost should be sufficient to ‘wake’ them.


  • Hyacinths, ‘Paperwhite’ daffodils, freesias, and Lachenalia corms can be planted in bowls now to achieve flowers for Christmas. Once they have put on 2.5cm (1in) growth, they can be taken into a cool room, only to be brought into a warm room in time to flower for the festive period. Bulbs sold as ‘prepared’ can be forced by plunging the planted bowls in a cold, dark place for a few months, then bringing them straight inside to flower.

Ventilate greenhouses and conservatories to their maximum to prevent soaring temperatures. Use shading if necessary.
In the greenhouse.

Move conservatory plants outside and hose them down to help with pest management.

Damp down greenhouses on hot days to maintain humidity levels.

Pest and disease watch

Many conservatory and greenhouse pests will be active during the summer months. Check plants regularly for signs of glasshouse whitefly, leafhopper, red spider mite, mealybugs and scale insects.

Clean up fallen leaves and spilt compost from benches and floors to prevent pests and diseases spreading.