I love this moment. When the sun slants and everything is mellow with ripeness; when the garden can’t quite decide if it is celebrating the last of the heat or the beginning of the cool. There is much to harvest, from seed to produce. Gather as much as you can into bottles, jars and the freezer; you may have had your fill of courgettes and runner beans, but deep in December their summer flavours will cheer up a dark night.
September is not all toil, though. It’s a time to take note and plan for next year, whether that’s visiting an inspirational nursery with a great display garden or scrutinising your own garden for gaps. Take photos on your phone, make notes and mark up the dud bits. Later in autumn, when you are digging up and dividing, you’ll have an excellent visual reference of what to move and what gaps need to be plugged. Meanwhile, here are some jobs to be getting on with.
Take semi-ripe cuttings
If you fancy a lavender-edged path or want to fill your garden with armfuls of herbs, this is the secret. This is particularly useful for plants that might not make it through winter, such as compact lavenders, tender pelargoniums, salvias and penstemons, as well as Verbena bonariensis, which tends to get a bit shrubby, rather than towering elegantly, if left for a second year. This kind of cutting also works very well for woodier herbs including bay, rosemary, rue, sage, thyme and hyssop. Semi-ripe cuttings have a woodier base than tip. Hormones are naturally high in plants in autumn and they should root quickly. The woody base means the cuttings are less likely to rot.
Select a cutting from this year’s growth and remove using sharp secateurs; place in a plastic bag to reduce water loss. It can be kept in the fridge for several hours until you are ready to prepare it. Take cuttings roughly the length of your secateurs, aiming to trim down to 10-15cm in length, cutting just below a leaf node. Then remove the lowest leaves and the soft tips. You should have about four leaves remaining. If you have hormone powder you can dip it in this, but I rarely use the stuff.
Insert the cuttings into containers filled with free-draining compost (mix compost 50:50 with sharp sand or perlite). Water well and allow to drain. Place pots in a greenhouse or on a warm windowsill out of direct light and cover with a clear plastic bag. Keep compost damp, but remove excess water that may develop in the bag.
Order garlic and onions
Garlic and overwintering onions are planted out from now till the end of October, but get your order in as soon as possible or you will be picking over the spoils. I’m a huge fan of overwinter onions; I like the Japanese Shensyu Yellow, and Radar for red onions. I find that garlic does best planted out as early as you can; Solent Wight and Cristo are both reliable and hardy. Onions need to be spaced 20cm apart each way; garlic is best at 18cm each way. Choose your sunniest spot.
Sow a lawn…
September is the perfect time to tackle those bald spots or start a new one from scratch. Lawn seed is a fraction of the price of turf and more environmentally friendly in terms of transportation costs. Ideally sow after rain, as grass seed needs slightly moist soil to germinate. But don’t sow if it’s too wet; the seed will just stick to your shoes.
Rake over the site to break up the soil, and top dress with a thin layer of peat-free compost if necessary. Check the sowing rate for the seed mix – it’s usually 50g per square metre. Don’t over-sow: it increases surface humidity and can lead to damping-off diseases. Scatter half the seed in one direction over the soil. Sow the other half at right angles to the first spread. Lightly rake over the seed bed, working backwards to avoid treading on the raked soil. Cover the area with netting otherwise you’ve just spread bird seed.
… or sow a meadow instead
Establishing a wildflower patch, or rewilding your lawn, means following exactly the same method as for a lawn. The pollinators will thank you and you’ll have flowers to pick. The simplest way to do it is to let your lawn grow long and flower, but that might just mean dandelions, so now is the perfect time to establish a little more diversity.
First, cut the grass short, and rake it hard to expose some soil. Sow yellow rattle (the seed needs to be fresh, so check the date): it is a semi-parasite on grass that will reduce the lawn’s vigour. Now insert plug plants of wildflowers; they will establish quickly. If you don’t fertilise the lawn, it will revert to something full of life.
Visit a nursery garden for late-summer colour
Some of the best nurseries have stunning display gardens. Gorge on great planting combinations, design ideas, and pick up the plants at the end.
• Dyson’s Nurseries, inside the beautiful Great Comp Garden near Sevenoaks in Kent, is home to hundreds of salvias that will sing right the way into autumn. It is inside the beautiful Great Comp Garden.
• Altamont Plant Sales and Nursery is nestled to the side of the wonderful Altamont garden. Its Corona North commemorative border is packed with inspirational late-summer colour.
• Old Court Nurseries, Picton Gardens, in Malvern, has the best aster breeding in the country.
• Derry Watkins’ Special Plants, near Bath, focuses on plants that love free-draining soil, a masterclass in having it all.
• Knoll Gardens, Somerset, is famous for its grasses and all the necessary flowers to pull off a new perennial movement garden.