Here’s some advice about what to consider for your garden during September.
General tasks and garden maintenance
Time to start your compost
To get your compost going buy a compost bin or build a partially enclosed and easily accessible area for a heap. It is vital to replace the goodness in soil and autumn produces quantities of garden waste that will add invaluable organic richness back into your soil for the coming spring.
Add a variety of different materials such as spent vegetable plants.
But don’t add diseased or pest-ridden material to your compost heap.
Clear up garden debris
It’s important to keep weeding. Most perennial weeds are susceptible to weed killer in September and systemic weedkillers will carry on working throughout the winter.
Clear any debris from your garden. Pests and diseases that overwinter in your garden will reappear next spring so dispose of them now.
Burn diseased material and put the rest of your garden rubbish – apart from woody stems – in the compost.
Clean your greenhouse
Once tomatoes and other greenhouse crops are over, give the greenhouse a good clean to prevent pests.
Dig clay soil
If your soil is heavy clay, start digging it over this month. Add lots of organic matter to improve the quality.
It can be left in a pretty rough state over the winter when the cold will break the lumps down, this makes spring planting easier.
There is always a possibility of warm weather in September which means it is important to water once or twice a week rather than little and often.
Containers and hanging baskets need watering everyday.
For recently planted large shrubs or trees leave a hose trickling around the base for an hour. Ensure trees or shrubs planted in the last couple of years on lawns or in areas of rough grass have a circle of clear earth around them. Keep these areas clear or grass will prevent essential moisture getting through.
Planting conditions of autumn are ideal because of the warm moist soil. So now is the time to plant container grown trees, shrubs and bulbs.
The key to successful planting is to water in well.
Soak the rootball in a bucket until no air bubbles come to the surface, dig the planting hole, fill with water and allow to drain away. Place the plant in the hole, fill with soil, firm gently and water well with a watering can – this will give the plant a huge advantage over one planted with a dry rootball in a dry hole and watered only on the surface.
Trees and climbers
Conifers and evergreens
Plant and move evergreens and confers. Dig a large root ball and wrap in hessian.
Plant to the same depth as before, firm in well and water generously.
If the new location is exposed or windy, protect the plant with a windbreak to reduce water loss from the leaves through evaporation.
Clip back hedges such as privet, hawthorn or yew, before mid September.
You should regularly deadhead roses. Prune climbing roses once the flowers have faded. You just need to cut back sideshoots from the main framework to a couple of buds. Remove any diseased, spindly, old and unproductive stems and tie new shoots onto supports at their base.
Reduce the frequency of mowing now and towards the end of the month, it’s time to ease off on this aspect of gardening for the moment. Rake out the old dead grass and moss by hand r with a machine. Spike to improve drainage again either by hand with a garden fork or with a machine, add a top dressing of soil/sand/compost mixed according to your soil type (ask for advice at your local garden centre if you are unsure) and feed with autumn lawn feed. This low-nitrogen feed strengthens grass in preparation for winter; do not use spring lawn feed as this encourages grass to grow and it may not survive the cold. After all this your lawn will look dreadful, but fear not, it will benefit enormously from the regime. Repair bumps, hollows, bald patches and broken edges too.
September is the time to start making a new lawn. Good preparation is vital whether you are sowing seed or laying turf. Remove weeds and stones, dig over, adding organic matter and fertiliser, rake smooth, firm by walking up and down and rake again at right angles.
Repeat the raking and firming process until the area is flat and the surface is a fine crumb texture.
Sow seed according to the packet instructions and lay turf in a brick pattern so no joints are in line. Water well and keep off for four to five weeks.
Bulbs, flowers and containers
This month is the best time for planting spring bulbs. Choose plump bulbs and plant within a week of buying in a location with good drainage.
Ensure pots and containers have plenty of crocks at the bottom.
Bury bulbs at twice the depth of their size, tip upwards and ensure there are no air pockets around them. Use them to fill gaps in beds and borders, in formal gardens, in pots and containers, under trees and shrubs or naturalised in grass or woodland.
Start with narcissi, alliums, and crocuses. Tulips should be left until November.
The last opportunity to plant indoor bulbs to be in flower for Christmas is mid September. Use bulb fibre or multi-purpose compost with a little added grit, set the bulbs as close as they can possibly be in a bowl at least 4″ deep, preferably with a drainage hole. Narcissi and hyacinths should have their noses just showing – all other bulbs must be covered completely.
Make sure the compost is well below the rim of the bowl and leave in a cool dark place inside. Don’t let the compost dry out and when the leaves are 1 – 2″ high move into a cool room; when flower buds appear move into full light – preferably again in a coolish room.
Plant new perennials and bring tender ones into shelter. While the soil is moist and warm, plant hardy perennials so their roots have a chance to become established before winter. Water well before and after planting and ensure you choose plants that are appropriate for your soil type. Lift and bring tender perennials inside before frosts cause any damage.
Deadhead dahlias, chrysanthemums, asters and any other spent flowers to keep the garden looking tidy and to encourage dahlias to reflower.
Autumn can be windy so make sure tall flowers are supported. Once perennials have finished flowering, cut them back and divide large clumps by lifting carefully and separating down the centre with two forks back to back. Replant with plenty of organic matter and water generously. Remember some perennials, such as peonies, loathe being disturbed so check before you dig them up.
Collect seed heads from trees and shrubs. Collect when nearly ripe – just as they are turning brown. Snip them off, put them in a paper bag, label and hang somewhere cool, dark and dry.
Pots and containers
Plant winter bedding and spring bulbs in your pots and containers now. Stop feeding permanent plants and move any tender plants under cover before the cold sets in.
Spring flowering bedding
Buy and plant out violas, wallflowers and primulas now for Spring.
Clear old summer bedding, incorporate some organic matter into the soil and plant in drifts.
Remember not to grow wallflowers and ornamental cabbages in the same spot two years running; they need rotation to avoid the root disease ‘clubfoot’, which is infectious and persists in the soil.
Pick vegetables when they are young – as they mature both flavour and texture become coarser and some plants, such as courgettes actually respond to harvesting by producing more flowers and fruits right into the autumn.
Plant overwintering crops such as garlic, salad and bulb onions, turnips, spinach and winter lettuces.
Harvest everything. Dig up root crops – apart from parsnips which taste better after a frost – and potatoes before slugs wreak damage – and dry thoroughly before storing in boxes or paper sacks. Fast maturing vegetables such as courgettes, cucumbers and tomatoes must be picked regularly or they lose their freshness and become stringy, tough and bitter.
Any outdoor tomatoes should be picked by the end of the month and ripened inside.
Marrows, pumpkins and squashes should be left in the sun for a few days to harden the skin and dry them off before storing in a cool, dark place.
Sow parsley, cut and freeze herbs in ice cube trays and pot up chives and mint for the winter. Lift a clump, divide and pot using multi-purpose compost. Cut back old foliage, water well and wait for your winter crop to appear
Harvest damsons, blackberries nectarines, apricots, early apples and pears. You can tell when they are ripe if they come off the tree with an easy twist and there are a couple on the ground.
Birds and wasps love fruit so think about investing in a fruit cage for next year if your crop is disappearing.
Cut fruited canes of summer raspberries and tie in any new canes for next year. Make sure you only keep the healthy canes and cut out weaker stems.
Plant new fruit trees from mid September onwards once any really dry weather is over. New trees prefer warmish soil to establish their root systems, especially nectarines and peaches. Other fruit trees can be planted later as they are less sensitive to cold.