September in the garden

September is a busy time in the garden. Things can quickly change from summer to the onset of winter, so if you are organised you can really get on top of jobs now to save time and work next spring and to prevent having to work in colder, harsher conditions.

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The Cutting Garden

Sowing and Growing

  • Plant out and transplant biennials.
  • Divide and replant perennials to ease any congested areas. Later in the month bring tender perennials, such as pelargoniums, inside to protect from the frosts.
  • Continue sowing hardy annuals for early flowering next year – you'll get bigger, better plants which can flower a good six weeks earlier than those spring sown. For example, briza, bupleurum, calendula, centaurea, Papaver rhoeasPapaver somniferum, and scabious can all be direct sown now. Remember to keep them weed free as they germinate. 
  • Clear your annuals as they go over and add them to the compost heap. 
  • Sow a pack of Viola 'Heartsease' to flower in about eight weeks' time, right through winter.
  • Hunt for self-sown seedlings of hardy annuals and biennials, such as English marigolds (Calendula), honeywort (Cerinthe) and honesty (Lunaria), where you’ve had them earlier this year. If they are overcrowded where they’ve sprung up, transplant them, spacing them 12in (30cm) apart. Or create a line in a cutting patch to harvest flowers next year.
  • It's urgent to get wallflowers in place now. These spring-flowering biennials need to get their roots down well before flowering.
  • Sow yellow rattle. This is key to the success of any wild flower patch as it reduces the vigour of certain grasses. We devised a good system at Perch Hill, creating circles of almost bare soil with a swish of a strimmer, then scattering seeds direct into these.

Bulbs and Tubers

  • Now is a good time to start planting your spring bulbs – the ground will still be nice and warm from the summer months, and it gives plenty of time for the new roots to bed in before the spring sunshine arrives.
  • Inside, have a go at forcing some hyacinths or amaryllis now for colour over the festive season.
  • Plant pots of smaller bulbs such as muscari, iris, crocus, chionodoxa, scilla and anemones. Keep watered during the winter if we have any dry spells (but lift off the ground to prevent waterlogging which is just as bad) to provide pots full of colour for the spring.
  • Plant a layered pot of bulbs, known as a “bulb lasagne”, for your doorstep, with the largest and latest flowering bulbs at the lowest level (with at least 6in of soil/compost below the bottom of the bulb) and early flowering, smaller bulbs on top. Excellent combinations are crocus above early tulips (e.g. single varieties such as ‘Prinses Irene’ and ‘Couleur Cardinal’), or try an early grape hyacinth (Muscari azurea) on top, with a late tulip (‘White Triumphator’) below. Top-dress with grit to keep the pot looking good through winter. Watch Sarah make a bulb lasagne in our video guide.
  • Plant small bulbs in to your lawn. Think of jazzing up an area of lawn or rough grass with crocuses such as C. tommasinianus, C. vernus and C. chrysanthus hybrids. All are happy in thick turf with the sun fully on them.

Harvesting

Lovely things to pick and arrange from your garden in September:

  • Bulbs: gladioli and acidanthera
  • Hardy annuals: Euphorbia oblongata, sunflowers and scabious
  • Half-hardy annuals and dahlias: all
  • Perennials: Euphorbia ceratocarpa, salvias, heleniums, phlox, echinacea, rudbeckias
  • Shrubs and trees: hydrangeas, Viburnum opulus, berries and leaves.

Pick a large bunch of late-flowering phlox, such as the pure white ‘Mount Fuji’. It thrives in sun and shade. Strip just the bottom leaves and pile tall stems into a simple jug. Add a teaspoon of bleach or slosh of vinegar to keep bacteria at bay. They will last more than a week.

Pick hydrangeas before they are damaged by wind and rain. To make them last as long as possible indoors, float the flowers overnight in a bath of cool water. Then arrange them in a vase with only an inch or two of water. As this evaporates, the flower heads will dry and keep their colour. If you want them to retain their texture but not their colour, add a drop of glycerine to the water too.

Pick a last bunch of roses before they brown. Sear the stem ends in boiling water before you arrange them to make them last as long as possible.


Perennials, Shrubs and Trees

Pruning and Tidying

  • Keep deadheading and weeding.
  • Collect seed from perennials and annuals and store them somewhere cool and dry.
  • Deadhead dahlias. Cut all the spent flowers off to the buds below them. With a little TLC, they’ll keep flowering until the first hard frost. Pick a few pristine heads as you go and arrange in small glasses or bottles on the dining table. While you’re at it, deadhead all your tender perennials – pelargoniums, arctotis, argyranthemums and trailing verbenas. This will give them a new spurt of life. Combine this with a feed of liquid seaweed or general fertiliser for an extra tonic.
  • Pinch out the tips of wallflowers to promote bushier growth.
  • Early chrysanths are a must in the garden, and will give you a decent few weeks of bloom before the worst of the autumn weather. The later flowering chrysanths are an asset if you have a greenhouse, where they can happily carry on flowering through winter, under cover.
  • Prune climbing/rambling roses once they've finished flowering. Remove suckers from the base of roses and trees. Remove any fallen leaves from the base of roses to prevent the spread of disease.

Planting

  • Later in the month plant spring bedding such as wallflowers, primulas and violas for a colourful spring display.
  • Start planting new perennials as well as trees/shrubs/climbers.
  • Plant pot grown new trees whilst the soil is still warm and moist.

The Kitchen Garden

Veg

  • When you think you’ve harvested your last potatoes, carefully dig over the veg bed, collect those that were still lurking under the surface, and then dig over ready to plant some green manures. These green manures are useful in many ways; they protect the soil from erosion over winter, reducing the potential of any leaching of mineral and nutrients, and also protect soil structure, as well as boosting nutrients when dug into the soil. They also provide a green carpet that helps provide shelter for beneficial insects through the winter, such as ground beetle, and if you leave a patch to flower they are loved by pollinators – Phacelia tanacetifolia for example, is one of the best nectar sources for the honeybee, bumble bee and hoverfly.
  • Bean and pea plants that have finished their harvest can be cut back, leaving the roots to be dug in to the soil to provide extra nitrogen for future crops.
  • Continue to feed tomato plants until all the fruits have finished growing and ripening. If your tomatoes refuse to ripen in miserable weather, then you could make a delicious green tomato chutney.
  • Sow spring onions – these will be ready to eat before the frosts get going in most parts of the country. Even if frosts are forecast, they are fine under glass or plastic to harvest through late winter and autumn.
  • Remove any crops that have finished leaving unneeded areas clear – weeding and tidying for the winter. Keep an eye on your brassicas for butterfly eggs and caterpillars; these will most probably be under the leaves.
  • Sow Swiss chard, winter spinach, broad beans and hardy peas.
  • Keep watering winter squash and pumpkins if the weather is hot. This will prevent their growth from being checked. Use stored rainwater wherever possible. Keep pinching out the tips of triffid-like pumpkins and squash. They prioritise vegetative growth over fruit formation, and you may get fruit drop if you don't keep them contained. With the tips pinched, all the fruit down to the base of the stem will now be ripening well. Place a tile under the largest fruit to stop rot creeping in where they sit on the damp soil. Leave pumpkins, squash and marrows to ripen in the sun as long as possible so that the skin can harden.
  • Prepare a bed for autumn-planted shallots. Incorporate well-rotted compost into the area to improve fertility. If your ground is wet, a raised bed may be a better option. Plant the sets from the end of the month, with the tip just protruding from the soil.
  • Do a last outside sowing of radish. With the soil still warm and moist with dew, you should be eating these in four to five weeks.

Salad and herbs

  • Direct sow a row of rocket. It seems late to still be sowing seed, but salad rocket does not bat an eyelid at the cold or wet. There’s no flea beetle around now either and the scourge of the slug and snail is on the decrease. Don’t just scatter the seeds willy-nilly, but space them a couple of inches apart, to make thinning (or transplanting excess seedlings to a second row) easy.
  • Sow all your autumn-winter picking salad leaves and herbs if not done in August.
  • Cut and hang herbs to dry for using in the kitchen over winter.
  • Sow coriander now and you may be harvesting until April or May next year. Sow in a row outside, or into a gutterpipe for planting out in a month’s time.
  • Long-season herbs, such as chives, lovage and sorrel, should all be cut to the ground. They will be up again in a couple of weeks with fresh leaves. Drench with slow-release, potash-rich liquid comfrey fertiliser to encourage strong regrowth.
  • If weather is dry, water well. Pot up less hardy herbs such as parsley, chives and French tarragon and bring inside into a sunny, frost free spot.

Fruit

  • Once harvested, it's time to start thinking about pruning back your fruit trees and shrubs to maximise yields next year. As a general rule of thumb the sooner this is done after harvesting the better.
  • Pot up strawberry runners to make new plants for next summer.
  • Cut back the fruited canes of summer raspberries, tying in the new green canes for next year’s crop.
  • If you are not sure when your apples are ripe, gently lift them in the palm of your hand or give them a gentle pull – they should come away easily from the branch without needing to be pulled hard.

Harvesting

Here's what you could be picking and eating this time next year or, if you're an old hand, already are:

  • Brassicas: kohl rabi and kale
  • Roots: radishes, carrots, maincrop potatoes, stored onions, beetroot
  • Salad crops: salad leaves, pea tips, all lettuce and Florence fennel
  • Edible flowers: nasturtiums, runner bean and courgette flowers
  • Leafy greens: chard and spinach
  • Legumes: peas, Borlotti, French and runner beans
  • Squash: courgettes, Red Kuri squash and Pumpkin ‘Munchkin’
  • Fruity veg: tomatoes, cucumbers, aubergines, peppers and chillies
  • Other veg: globe artichokes and sweetcorn.
  • Herbs: all
  • Fruit: autumn raspberries, plums, damsons, first cobnuts and walnuts, apples and first quince and pears.

Pick figs as and when they ripen, bottling them in vodka if you can’t eat them all fresh. They can be sliced to serve as a delicious topping for vanilla ice cream, and you can drink the spirit as you would sloe gin.

Pick gluts of damsons, plums and apples to make jams, flavoured gins and chutneys in preparation for the coming winter. Store in good airtight bottles and jars and they’ll last for months.

Harvest all your sweetcorn, blanch and freeze. Strip the husk and blanch the cobs in boiling water for four to six minutes, depending on size, and then cool immediately in cold water. You can store these in the fridge for up to five days, or freeze them.

Discover Sarah’s favourite recipes for September, including her favourite herb salad with halloumi and chorizo, tarragon vinegar and blackcurrant mousse ice cream.


Other jobs

  • Try to keep your borders and lawn free of dead leaves. Collect them up in to leaf mould bags, dampen the bags and store in a corner of the garden for a year – then turn out perfect leaf mould.
  • If you’re not happy with your lawn, now is a good time for a bit of TLC. After mowing, scarify with a lawn rake, then fork and brush sand into the holes. Choose a suitable lawn seed, then sprinkle over, followed by a thin layer of compost. Water well and cover loosely with fleece to keep the birds at bay.
  • Create a new lawn from turf or seed – autumn is a good time to do this.
  • Continue to feed and water containers and water any newly planted perennials until established.
  • Make notes/take photos/draw plans of your flower borders and vegetable plot to help plan for next year. Think about and make a note of what worked (and what didn’t!) and the combinations you would like to try or plants that you would like to remove or add to.
  • Visit a good local garden that is open to the public and take a notebook so you can jot down the plants looking good at this time of year. Then go home and think about how you could integrate them into your own patch to improve its performance year round.
  • Order bare-rooted roses for delivery later in the autumn.
  • Give meadows a final cut before the winter, aiming for 7.5cm (3in) height, and letting the clippings lie for a couple of days before raking (to allow wildlife to crawl back into the sward).Annual meadows do not need mowing.

In the greenhouse

  • Bring pots of late-flowering chrysanthemums into the greenhouse along with any tender perennials for overwintering, to protect from the frosts.
  • Clean out your greenhouse to reduce the risk of pests and diseases overwintering.
  • If temperatures drop, close doors and vents over night to keep it as warm as possible.
  • Towards the end of the month As light levels fall, remove shade netting from greenhouses or wash off shade paint. Cucumbers will crop into autumn so close vents and doors overnight to keep in the warmth.
  • Water plants sparingly, but damp down the greenhouse by watering the floor each morning. The humidity will mean you have to water less often.

Wildlife and pests

  • Birds, who have been pretty sedentary during the summer, will now start to turn back to the bird tables and feeders in order to stock up for the approaching colder months, so start to top up any food for them regularly. Before you do, give everything a good clean – many birds die each year from parasites and toxic bacteria that can build up in feeders and water containers if not regularly cleaned.
  • Plant hardy annuals and perennials that attract insects.
  • Fallen fruit that is starting to go over can be a veritable feast for birds and insects alike. Pop an apple on a fat ball feeder (like our Heart-shaped Bird Feeder) and leave gone over sticky plums and damsons out for butterflies who will adore them.
  • Check your dahlias for signs of earwig damage. Catch earwigs in upturned pots crammed with newspaper or straw on canes among the plants, and destroy any you find.