Gardeners diary for May
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General tips
  • Grow annuals and flowering herbs which encourage beneficial insects into your garden.
  • Soil that has been flooded in previous months will be compacted. If it has dried out sufficiently, aerate the soil by spiking deeply with a garden fork, but take care not to damage surviving plants or their roots.
  • Keep your eyes open for pests and diseases in the greenhouse and the garden, and take appropriate action immediately to stop the problem getting out of hand.
  • Weed regularly.
  • If the weather is dry be prepared to water new plants, seedlings and other vulnerable plants.
    Be ready to protect young and vulnerable plants if frost is forecast.
  • Ventilate the greenhouse and apply shade paint towards the end of the month, and damp down if the weather is hot


  • Sow a new lawn early in the month if not done in April.
  • For established lawns you can progressively lower the mower blade.
  • Trim lawn edges each time you mow.
  • If not done last month, re-cut and repair ragged edges.
  • Apply a spring lawn fertiliser and, if necessary, a weedkiller to established lawns.
  • Alternatively treat weeds individually with a spot weeder or dig them out with an old knife.
  • Remove any coarse grasses by hand.


  • Finish planting and replanting aquatic plants.
  • Skim off algae
Beds & Borders

Annuals and biennials

  • Make a final sowing of hardy annuals, including candytuft, clarkia, cornflowers, ornamental grasses, larkspur, love-in-the-mist, night-scented stocks and mignonette.
  • Plant out sweet peas, if not done in April.
  • Support tall-growing hardy annuals.
  • Begin to harden off half-hardy annuals and bedding plants previously sown under glass.
  • In milder areas plant half-hardy annuals and bedding plants towards the end of the month.
  • Sow biennials in nursery rows
  • Plant out seedlings of Foxglove, Sweet William, Forget-Me-Not, Wallflower, Polyanthus
  • Do not plant out any tender species until hawthorn and laburnum are blooming


  • Put plant supports and stakes in position.
  • Remove weak new shoots from dense-growing perennials, such as phlox.
  • In colder areas plant new perennials and cut back evergreen ornamental grasses.
  • Sow new perennials in nursery rows.
    Finish planting out early-flowering chrysanthemums.
  • Lift and divide spring-flowering perennials as necessary, and trim off dead, straggly growth.
  • Revitalise aubrieta, gold dust and similar vigorous spring-flowering rock plants by cutting them back hard.


  • Allow foliage of spring-flowering bulbs to die down naturally; lift and heel them in, in an out-of-the-way corner if you need the space.
  • Stake tall-growing lilies
  • Dead-head spent daffodils. Remove the seed pod and the old petals.


  • Spring feed bush and climbing roses.
Shrubs, Trees and Climbers
  • Check tree ties.
  • Check mulches and replace if necessary.
  • Trim hedges after checking for wildlife.
  • Feed container-grown shrubs and perennials
  • Prune back the branches of fig trees. Rub compost into the cut to prevent bleeding
  • Clip bay trees
  • Hang out pheromone traps to prevent apples being ruined by tunnelling larvae.
  • Stifle side-shoots of raspberries with pruning, and water all soft-fruit bushes and fruit trees.
  • Prune grape vines to encourage better setting of fruit.


  • Sow new herbs such as coriander, dill and parsley in situ.
  • Sow basil under cover
  • Take cuttings of rosemary, sage and thyme. Make them 10cm long and put them in gritty compost in a sheltered, well-lit spot in the garden.
  • Erect supports for runner beans and climbing French beans. Make sure they will not cast shade over plants that like the sun.
  • Sow beetroot, cabbage, carrots, kale, parsnips, peas, radish
  • Begin earthing up potato plants.
  • Pinch out the tops of broad beans to discourage blackfly attack.
  • Protect roots of brassicas against cabbage root fly with artificial barriers such as card collars.
  • Plant out celeriac, celery, sweetcorn, runner beans and other strong plants grown under glass. Mulch well.
  • Protect carrots against carrot fly with two-foot barriers of fine netting or clear polythene.
  • Plant fruiting vegetables under cloches.
  • Put up the sticky traps for whitefly. You can't be too early with this.
  • In a cold greenhouse you can now sow: basil, coriander, French beans, courgettes, pumpkins, tomatoes (still), sweetcorn, runner beans, marrow, gourds, parsley, lettuce, rocket
  • In a cold greenhouse you can now plant out seedlings of: cucumbers, peppers, chilli, tomatoes, rocket basil but watch the night-time temperature. Heat to as near to 10 Celcius as you can.
  • Feed greenhouse tomatoes and circubits, removing growing tips and side-shoots as necessary.
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