September is arguably my very favourite month in the garden, and certainly one of the busiest. Yes, perhaps it doesn’t hold with it the excitement and anticipation of April or the contentment of seeing everything reach a crescendo by mid June, but it’s gentle mellowness, the light now lower in the sky, the occasional BBQ on a balmy evening and the gentle slide from summer into autumn makes it a contemplative and often satisfying month. On a personal note, it’s also when my own terraced garden, tiny at just 6x7m2looks at it’s very best, crammed full of exotics, grasses and late-season perennials, gently building up steam to a thrilling climax to the season. The month itself does indeed see lots to be done. The fruit and vegetable garden is bursting at the seams, with plentiful harvests to be had wherever you look, planting takes up a fair amount of time, be it with perennials, bulbs, trees or shrubs, there’s hedges to trim, ponds to ready for winter, lawns to deal with, and so on.
I hope you find this months guide to what you might like to do in your garden useful. It’s by no means an exhaustive guide but hope that in some way it might inspire you to get out there on a warm evening and take in the gentle beauty that September so often holds.
Lift, split and divide tired or overgrown herbaceous perennials
By lifting each clump and splitting it into smaller sections, replanting should result in increased flowering next year, reinvigorating the plant at the same time.
Replant each division with a generous handful or two of garden compost, firm in well and water in. Most perennials benefit greatly from this simple propagation technique every 3-4 years.
Tidy up perennials
Continue to cut to the base those looking untidy. Any that might provide structure over the winter are best left for later on.
September is the traditional month to plant hardy spring-flowering bulbs such as Daffodils, Hyacinths and Alliums.
When selecting bulbs, they should be of good size, plump and firm, with no sign of rots or mould.
When planting bulbs, do so deeply – a general rule of thumb is 2-3 times the height of the bulb itself, incorporating a little grit if your soil is on the heavy side. Most bulbs like an open, sunny position to perform at their best.
Use large drifts of single varieties for maximum impact,as well as to avoid a cluttered, chaotic look. Alternatively, go for two or three varieties planted generously and woven through shrubs and perennials.
Many bulbs can be forced indoors, but Hyacinths are the most frequently used.
Buy the bulbs now and pop them into the fridge for 4+ weeks before planting in shallow pots/pans. Pack them in closely together with the tips protruding just above a mixture of multipurpose compost and grit. Pop into a dark, cool place such as the shed or garage, keeping half an eye on them for the next 10-12 weeks or so. As soon as the shoots are firm and plump, bring indoors and place a few twiggy sticks around the edge of the pot to keep the blooms upright. They’ll quickly come into flower on a bright, warm windowsill.
Whenever out in the garden, look out for seed to collect from favourite annuals and perennials.
Simply get a paper bag, shake seed into it and take indoors. Spread the contents out onto a sheet of newspaper, separate the chaff, before labelling and storing in an airtight container for sowing next spring.
Prune Rambling Roses
Now that flowering is over, start by pruning out dead, diseased or damaged growth. Thereafter, remove the oldest stems, tying in as horizontally as possible this year’s growth whilst it’s still nice and pliable.
When pruning late in the season, consider taking cuttings of favourite varieties.
Replace summer bedding
As bedding in containers and baskets starts to look a little tired, replace with autumn/winter bedding. Garden centres and nurseries will be awash with the likes of cyclamen, heathers, pansies/violas, primulas/polyanthus, bellis, ornamental cabbages etc. Underplant with bulbs such as dwarf narcissus, tulips or crocus to prolong the display.
Plant out seed-grown wallflowers
Or look out for bare-rooted clumps in garden centres from the end of the month. Keep well watered for the first few weeks.
Trees and shrubs
Plant trees and shrubs
Autumn is the best time of year for planting trees and shrubs. Whilst container-grown stock can be planted at any time of year, it is now that plants begin to slow down and are thus under less stress when planted, most notably evergreens. Bare-root stock will be in garden centres from next month.
Dig as generous a planting hole as possible, incorporating plenty of organic matter into the base of the hole, as well as adding a handful or two of bonemeal. Firm in well with the sole of your boot and keep well watered.
Trees should be staked and tied in, particularly on more exposed sites, as well as being fitted with a tree guard should rabbits or deer be a problem.
Move deciduous and evergreen shrubs
Lift as much of the root ball as possible, keeping well watered until firmly established.
Trim hedges and topiary
The last of the season’s hedge trimming should be completed in September/October. Evergreens such as Box, Yew and Bay should be trimmed as soon as possible, whilst deciduous hedges such as beech and hornbeam can be tackled later on.
Look out for propagation material post-pruning – a few sprigs of Box or Yew ‘dibbed’ into pots of cuttings compost can be set aside in a sheltered pot and potted on next Spring.
Tend to Camellia and Rhododendrons
Flower buds will now be forming so keep well watered for the next couple of months, particularly if grown in pots. Treat container-grown ericaceous plants by replacing the top few inches of compost, as well as to a feed of Sequestered Iron.Try to always water with rainwater as tap water is too alkaline – investing in another water butt will ensure a regular supply is close at hand.
Care for Tomatoes
Pinch out the growing tips of cordon grown tomatoes (those with a single stem grown up a support) as further flowers are unlikely to set and ripen into well-formed fruits.
Remove any leaves shading the ripening trusses.
Inspect regularly for symptoms of the dreaded Tomato Blight. Look out for black streaks on stems and leaves, as well as burnt looking patches on the fruits. Remove all signs of affected material and dispose of immediately.
Feed Sweet Peppers
Continue to feed greenhouse peppers with a high potash feed (ie a proprietary tomato fertilizer such as ‘Tomorite’), as well as cutting down on watering to perhaps 2-3 times a week.
Lift Maincrop Potatoes
Lift and store the maincrop potatoes. Do so with a garden fork before leaving on the soils surface on a dry day for the skins to dry out. Store in paper or hessian sacks in a cool, dark place such as the garage and check from time to time as to their condition.
Push a thumbnail into a couple of kernels – if they ooze a clear liquid they’re still not quite ready. If the liquid’s a milky colour, they’re ripe and good to go.
Look out for bulbs in garden centres to be planted out from the end of the month. Cloves should be planted 1½ -2” deep, some 4-6” apart, in rows 12” apart.
Sow Salad Leaves
Hardier, cool-season varieties of oriental salads such as Chinese cabbage can still be sown now, as well as winter spinach, spring cabbage and endive. The likes of winter spinach will need some protection from mid-late October onwards. Either use a little straw or ready-made cloches/tunnels to help crops through the colder months.
Cabbages, Brussels sprouts and calabrese now need protection from pigeons. Simply drape bird-proof netting over vulnerable crops.
Cut down Asparagus fronds
Cut down the airy foliage on stands of asparagus once it starts to brown. At the same time, weed carefully and cover the area with a generous mulch of whatever organic matter you can lay your hands on.
Obvious candidates are the legumes (pea/bean family). Simply leave a few pods to ripen on the plant and let them dry there, before picking, bagging up and labelling for next year.
Other vegetables can be left to flower before harvesting their valuable seed. Lettuce, onions and leeks are good examples, particularly with heirloom varieties, or simply those that performed well for you. Remember that F1 varieties won’t come ‘true’if grown from harvested seed.
Sow Green manures
Early autumn is the ideal time for sowing many green manures. They’ll protect soils from erosion over winter, inhibit weed growth, and can be dug into the soil later in the year or in early spring to increase soil fertility.
Winter tares, Field beans and Annual ryegrass can all be sown now – clear a spot in the kitchen garden, rake over the soil, broadcast sow and water in. Simple!
Harvest top fruit
Apples and pears will now be ripe for picking in most cases. Gently cup a fruit in the palm of your hand and gently twist. If it comes away easily then it’s fully ripe. Store unblemished varieties that ‘keep’by wrapping individual fruits in old newspaper and pop into boxes or baskets in a cool place such as the shed or garage. Better still, invest in a ready-made apple store. Either way, inspect fruit regularly for any signs of deterioration, particularly brown rot.
Good ‘keeping’apples include ‘Braeburn’, ‘Sturmer Pippin’ and ‘Spartan’, usually the later varieties and often quite happy in storage until the New Year.
Late-season pears should also be picked by the end of the month, usually around the time that windfall starts. These will happily ripen in storage.
Plums always freeze well so pick remaining fruit as soon as possible.
With all top fruit, it’s good practice to wrap greasebands around the base of trees now. Wrap bands around the trunk and limbs 2-3’ from the ground to stop climbing winter moths laying eggs in the trees.
Lift and pot up rooted strawberry runners. Do so only with stock showing no sign of virus’(usually indicated by mottling of the leaves). Select rooted runners, detach from the mother plant and pot on into 7-9cm pots of multipurpose or John Innes No.2 before placing in a sheltered spot or cold frame for the winter.
Tend to Raspberries
Net autumn raspberries if birds are a problem. Look to pick fruit as it ripens, freezing surplus fruit on flat trays before bundling together in bags.
Cut to the base the fruited stems of summer varieties if you haven’t already done so. At the same time, space evenly and tie in the strong new shoots for fruiting next year. Dig out any runners appearing more than 12” from their supports.
Take final cuttings of the likes of Lavender, Rosemary, Bay and Sage. The first two often‘take’ better with a ‘heel’ attached to the base of the cutting.
Prune lavender plants after flowering. Individual plants can be lightly trimmed with secateurs, whilst hedges or larger shrubs are best tackled with a pair of shears. Never cut into the old brown wood. Bear in mind that lavender becomes increasingly woody with age and should really be replaced every 5-6 years or so. Plants bought for no more than £2-3 in 9cm-1 litre pots and planted in spring will quickly catch up older, straggly specimens if given a well-drained soil in full sun.
Sow/lay new lawns
September/October are the ideal months of the year for laying turf, sowing grass seed and repairing existing lawns.
When laying turves or sowing from seed, ground preparation is paramount. Begin by digging over the whole area, removing all traces of perennial weeds and large stones. Thereafter, rake over until roughly even before treading over the entire area to create a solid base with few air pockets. Next, gently rake over again, ensuring as flat a surface as possible results.
Turves should be laid in a brickwork-like pattern so that joints are staggered, whilst the turves themselves should slightly abut one another to allow for natural shrinkage as they establish. Make sure too to tamp down well with the back of a rake to ensure good contact with that finely raked topsoil underneath.
It’s also a good time to re-sow worn out areas and treat leather jackets. These troublesome lawn pests leave otherwise healthy swards with noticeable yellow patches.
Established lawns should now require less frequent mowing. Look to gradually raise the height of your mower’s blades over the coming weeks as growth begins to slow.
Look to feed your lawn at this time of year with a fertilizer high in potassium to toughen it up. Avoid spring lawn feeds high in nitrogen as they’ll simply promote lush, weaker growth more susceptible to disease.
Tidy ponds for winter
Late summer and autumn are a great time to tidy the pond in readiness for winter. Clear out any submerged foliage, as well as cutting back the plants themselves. Thin out oxygenators, plant marginals and divide plants such as water lilies. Take a little time to cover the pond with netting before overhanging trees drop their leaves in the weeks to come.
Take down nest boxes
Clean, dry and re-hang. Look to reposition any that were left idle this year.
Put up hibernation boxes
For insects such as ladybirds, lacewings and solitary bees - all valuable garden allies.
Sort out the greenhouse
Remove any shading paint applied in early summer, clean out thoroughly with disinfectant, replace broken panes etc before bringing in tender plants for the winter. Check that heaters are working properly, as well as ordering in surplus paraffin/propane if required.
Erect leaf bins
Leaf mould is a valuable soil conditioner and great added to potting mixes – don’t let your fallen leaves go to waste this autumn! Alternatively, invest in leaf sacks to store your fallen leaves.
Clean patios, decking and paths
Either scrub clean with a patio cleaner such as ‘Armillatox’ or use a pressure washer, often available to hire by the day/weekend. It’ll improve their appearance and stop hard surfaces becoming slippery over winter.