Your August gardening to-do list

Everything is growing very fast now, with plenty of harvesting, deadheading and seed-collecting to be done.  Here’s how to keep the garden looking good into autumn.

  1. Keep deadheading annuals, perennials and repeat flowering roses, cutting penstemon flowers back to just above a leaf to encourage more flowers.  Deadhead lilies for better flowers next year.
  2. Trim back faded perennials to keep borders tidy, especially if they’re smothering other plants or have collapsed onto the lawn.  Herbs such as oregano can be cut back to encourage a new flush of leaves.
  3. Trim lavender plants after they've finished flowering, taking off the old flower spikes and about 2.5cm of the leafy growth to keep the plant bushy.  Most hedges can be given their final trim towards the end of the month now too, as they won’t grow much after this.
  4. Complete summer pruning of wisteria, pruning all the long side shoots to five or six buds from the main stems to encourage next year’s flowers.
  5. Leaving some seed heads allows the plant to self-seed, but it’s also useful to collect seed, spreading them out on paper to dry before storing them for next year. 
  6. Continue taking semi-ripe cuttings from shrubs like fuchsia and choisya, taken when the base of the young shoots are beginning to turn woody.  Take cuttings of perennials that don't divide easily, such as penstemon.
  7. 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.
  8. Continue watering and feeding containers and feed shrubs and perennials with a high potash feed.  If you’re going away, group containers in the shade to share humidity and make it easier for neighbours to water them.
  9. Begin planting bulbs such as daffodils, colchicums and Madonna lilies.
  10. Continue to weed and water crops, harvesting onions when the foliage goes brown and freezing beans.  Continue to sow spring cabbages and summer prune trained fruit trees.