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Seasonal jobs for the month: September
1. Continue deadheading late-season bloomers such as Dahlia and Salvia to keep them flowering to the first frosts
2. Allow winter squashes (such as Cucurbita pepo ‘Li’l Pump-ke-mon’) as long as possible to ripen on the plant (but harvest and store before the first frosts)
3. Herbaceous perennials may be lifted and divided now to propagate and rejuvenate them.
4. Plant up containers for winter and early spring colour. Underplant winter bedding in containers with spring bulbs, such as tulips or crocuses
5. Begin clearing spent plants and dead or dying leaves, and give a general tidying to the garden to prevent pests and diseases overwintering.
6. Make, buy or prepare your compost bin to receive plant debris from autumn garden clearing for converting into useful compost.

Kitchen garden

  • Harvest sweet corn; the kernels contain a milky liquid when ripe.
  • Lift and harvest main crop potatoes; storing them in a cool dry place for future use.
  • Sow fast growing oriental greens such as tatsoi, pak choi and mizumi.
  • Plant sets of overwintering onions.
  • Strawberry plants can be established before the winter.
  • Sow late salad crops of lettuce and spinach for picking leaves next spring.
  • If your soil is heavy clay dig this month to allow time for weathering which will improve its structure in readiness for planting next year.
  • Extend the cropping season of runner beans and courgettes by picking regularly.

Glasshouse & Indoors

  • Clean the greenhouse thoroughly removing moss, grime and algae to reduce potential for pests and fungal infection of greenhouse plants
  • Reduce shading in the greenhouse to now that the sun’s strength is waning.
  • Make room for lifted tender plants and bring them into the glasshouse.
  • Early September is the last opportunity for forcing bulbs for indoor Christmas flowers.
  • Remove leaves from below bottom truss on tomatoes to reduce disease.

Pest, disease and disorder watch

  • Encourage insect eating birds to visit your garden regularly by installing a feeding station.
  • Biological treatment of vine weevil larvae using nematodes, can still be undertaken this month
  • With cooler conditions this month, water indoor plants early in the day so that leaves are dry by nightfall and so minimise the risk of fungal infections.

Trees and shrubs

  • Start the planting of trees and shrubs at the end of the month for establishing while the soil is still warm.
  • Shrubs may be lifted at the end of the month if required and re-sited elsewhere in the garden

Flower garden

  • Plant daffodil bulbs for spring flowering.
  • Tackle bindweed and other perennial weeds by treating them with glyphosate
  • Semi-ripe cuttings of many shrubs may be taken now.
  • Take cuttings of half-hardy or tender plants and overwinter the young plants under cover.
  • Hardy annuals such as sweet peas can be sown this month for stronger flowering plants next year

Ponds and water features

  • Where possible, cover garden ponds with netting to prevent falling leaves polluting the water.
  • Thin out congested aquatic plants such as fast growing oxygenators this month.
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