September is one of the best gardening months of the year. The days are warm and sunny while nights are refreshingly cooler. Veg plots are brimming with produce ripe for harvest and borders are billowing – summer’s last hurrah. Read on to find out how to keep the show going with this month’s garden maintenance tasks, and get your garden ready for the cooler months.
Start a new lawn from seed
This is the perfect month to sow a new lawn from seed. Dig the area over (check out the Gardening jobs for August blog for seed bed preparation tips), tread the area to firm the soil then rake the site level, removing any debris. Sow grass seed evenly then lightly rake it into the surface, keeping the seed bed well-watered as grass germinates and takes root. With established lawns, cut grass short under fruit trees, so you can spot and remove windfall fruits before they rot. Also, for mature lawns only, apply an autumn lawn feed. Unlike spring feeds which are high in nitrogen to encourage growth, autumn feeds are rich in potassium which helps lawns to survive the ravages of winter.
Plant spring-flowering bulbs
They say the early bird catches the worm, and the same theory applies to gardeners shopping for spring-flowering bulbs such as daffodil and crocus. Visit garden centres now to get hold of the biggest, firmest, plumpest bulbs, and get bulbs in the ground while the soil is still workable. Don’t be tempted to plant tulips this month though – wait until late October or ideally November, because early planting can encourage a fungal disease called tulip fire that results in distorted leaves.
Sow hardy annuals
For many gardeners, spring marks the start of the seed-sowing season, with every windowsill crammed with propagators by Easter! However, by direct-sowing hardy annuals outdoors now – plants that bloom and die in the space of a year but can survive winter frosts – gardeners will benefit from earlier flowers next summer and are often rewarded with more vigorous plants. Prepare a weed-free, raked seed bed then sow popular hardy annuals such as poppies, calendula, nigella and larkspur.
Remove pond weed
Blanket weed can build-up to unacceptable levels over summer, so give ponds a tidy-up before winter. Carefully insert a bamboo cane into the water and twirl dense patches of weed around it before lifting the bundle of growth from the water. Leave blanket weed on the edge of ponds for a few days before disposing of it, so any wildlife inadvertently removed can crawl back into the water. Ponds should be netted before autumn sets in, to prevent leaves from falling into the water and affecting nutrient levels as they decompose.
Help crops to ripen
As the days grow shorter and sunlight weakens, gardeners can give edibles a helping hand to ensure crops ripen. Pinch out the tops of cordon tomatoes, reduce watering and remove leaves that are overshadowing trusses of green fruit. As pumpkins and squashes swell rapidly, cut off leaves that cast shade over fruits to assist with ripening. Hungry birds (especially pigeons) can wreck brassicas as autumn turns to winter, so cover crops such as Brussels sprouts and cabbages with netting to prevent damage.
Seeing trees laden with fruit is a treat, but don’t go yanking crops from branches or you risk damaging the tree! Hold apples and pears in the palm of your hand, lift the fruit and gently twist it so it comes away with the stalk. Pears may need a week or two indoors to fully ripen before eating. While apples and pears will appear firm at harvest time, plums should be soft and may need to be picked over a period of weeks as fruits gradually ripen.
Remove greenhouse shading
With the nights drawing-in fast, gardeners need to make the most of every hour of sunlight, so remove greenhouse shading to maximise light penetration through the glass. Temperatures can drop sharply at night in September, and the risk of frost increases too, especially in the north. Get into the habit of closing greenhouse vents and doors before dusk – and if temperatures are forecast to dip, bring tender plants under cover.
Sow winter vegetables
Once summer crops such as runner bean and tomato plants have been consigned to the compost heap, veg plots often lay barren over winter, but there’s no need for your kitchen garden to be unproductive during the cold months. Onion sets for autumn planting are perfect for getting into the ground in September – onion ‘Shakespeare’ is an excellent variety for good size bulbs. Order seeds of broad bean ‘Aquadulce Claudia’ now (although it’s best sown from October) while autumn sowings of hardy salad leaves such as rocket, mustard and land cress are a must for winter nutrition.
Divide herbaceous perennials
If clump-forming perennials look tired and flowering displays have been lacklustre, plants may benefit from autumn division – a proven technique that rejuvenates growth and provides an opportunity to expand your stock of plants. Traditionally, gardeners were taught that hardy herbaceous plants which bloom before Midsummer’s Day should be divided in autumn, while those that flower after mid-summer can benefit from spring division. There are exceptions, so check your variety in a reference book. Use a fork to lift the clump, so roots are visible, and gently pull apart (large clumps may need two garden forks, used back-to-back, to prise roots apart). Plant divisions promptly and keep them well watered.
Winter-proof container plants
Once temperatures are cooler, reduce watering of container plants. Remove saucers from underneath pots that acted as reservoirs during summer and raise tubs up on pot feet – it’ll help with drainage and prevent compost from becoming waterlogged during winter. Where bedding plants are still blooming in pots, window boxes and baskets, don’t bother feeding to prolong displays – it’s too late. Instead, dead-head regularly to keep fresh blooms coming, and cut away any diseased or dying foliage.
What other gardening jobs do you do in September? What else looks like it needs doing in your garden this month? Let us know in the comments. As the weather gets colder, we will have winter gardening tasks for you to do in the coming months, be sure to subscribe to our newsletter so you don’t miss out!
Marc Rosenberg bio
Marc Rosenberg is a freelance garden writer and editor. A former journalist with Amateur Gardening and Horticulture Week magazines, he holds seven Garden Media Guild Awards. Marc has written for publications including The Garden magazine, BBC Gardeners’ World and RHS online.