What to do in the garden in September

01The priority jobs, in order

1. 1
   Plant spring-flowering bulbs — but not tulips yet. Daffodils, crocus and hyacinths go in now; the RHS advises planting them preferably by the end of September while the soil is warm enough to root them. Tulips are the exception: wait until November. Planting tulips late helps them dodge tulip fire, a disfiguring fungal disease. So buy your tulip bulbs now if you like the choice, but keep them somewhere cool and dry and hold off planting.
2. 2
   Help the last tomatoes ripen — and watch for blight. As nights cool, ripening slows. Remove some of the leaves shading the trusses so light and warmth reach the fruit, and stop feeding. If blight threatens — brown blotches on leaves and fruit, spreading fast in damp weather — pick everything you can and ripen it indoors. Green tomatoes make excellent chutney, so nothing is wasted.
3. 3
   Keep harvesting, and start storing. Apples and pears are coming ready. Test with the classic twist: cup the fruit, lift and gently turn — if it parts easily from the branch, it's ripe. Store only unblemished apples, not windfalls, somewhere cool and frost-free, ideally not touching. Lift maincrop potatoes before slug damage worsens.
4. 4
   Divide congested perennials. If clumps of hardy perennials have gone bare in the middle or flowered poorly, September's warm, moist soil is ideal for lifting and splitting them. Replant the vigorous outer sections, water them in, and you get more plants for free.
5. 5
   Sow hardy leaves and green manures. There's still time to sow winter salads — spinach, winter lettuce, rocket and mixed leaves — for pickings through the colder months, under cover if you have it. On empty beds, sow a green manure such as winter tares or ryegrass to hold onto nutrients and protect the soil until spring.
6. 6
   Plant new strawberry runners. Now is a good time to establish new strawberry plants so they settle before winter. Cold-stored runners can also be ordered now for spring delivery if you'd rather fast-track next year's crop.
7. 7
   Trim lavender lightly — never into old wood. Just after flowering finishes, tidy each lavender plant by removing the spent flower stalks and about 2.5cm (1in) of leafy growth. Do not cut back into the bare, woody stems: lavender rarely regrows from old wood, and a hard cut can kill the plant.
8. 8
   Order and plan your garlic. Garlic wants autumn planting — October into early winter — because many varieties need a cold spell to bulb up well. September is the month to choose varieties and get cloves ordered so you're ready to plant on time.