Garden Diary: August

Watering is vital this month, not only for containers and glasshouses but for new planting and flowers or shrubs close to a wall.

Bulbs and flowers

Deadhead pelargoniums and other summer bedding plants.

Continue to dead-head perennials and cut back when flowering is over.

Dead head dahlias regularly, taking care not to remove new buds further down the stem.

Keep an eye out for powdery mildew on susceptible perennials, like phlox, knautia and monarda. Spray to control it and cut back hard when the flowers are going over.

Collect seed from your favourite plants. Harvest when the seed pods are dry.

Start planning your spring bulb plantings. They are very good value, easy to pop into small gaps and will soon be in the shop.

Greenhouse and containers

Keep containerised plants well watered (daily in hot weather) Deadhead and liquid feed weekly to keep them flowering.

Damp down the greenhouse floor every morning on hot days

Be vigilant for pests like red spider mite and take quick action.

Take off lower leaves from tomatoes so that light and air can reach the fruits and continue to remove shoots from leaf axils..

Trees, shrubs and climbers

Water camellias and rhododendrons which are making buds now.

Keep hydrangeas moist and add a hydrangea colourant to blue varieties for a more intense blue next year.

Trim lavender plants now to keep them bushy, but don’t cut into old wood.

Do any necessary pruning on ornamental and fruiting cherries while the weather is hot and dry.

Check roses for diseased leaves – pick off and burn them.  Spray for mildew if necessary.

Continue to prune summer-flowering shrubs as the flowers fade.

Prune wisteria if missed last month.

Check  clematis and honeysuckle for mildew. Cut back if necessary.  Training to provide maximum airflow will help prevent it.

Trim evergreen hedges.


Summer prune restricted form fruit trees (fan, espalier) by cutting back side shoots to about five leaves from their point of origin.

Support heavily laden branches on plums, apples and pears with wooden props. Thin out fruit as necessary.

Start to harvest early apples.

Prune out fruited canes of raspberries.

Prune blackcurrants after fruiting, removing about a quarter of the oldest stems.

Plant strawberry runners into fresh beds.


Keep birdbaths filled with fresh water and flush out any algae.

Top up ponds and aerate in hot conditions. Remove algae and blanket weed .

August is the best month for butterflies – look for them on buddlejas. If you don’t have space for a full sized one, try one of the Buzz varieties. Available in ivory, magenta, lavender or light blue. They are much smaller and flower over a long period.