Summer is coming to an end is not an excuse to neglect your garden. Here are the six things you need to do before autumn to keep your plot looking gorgeous as you see out the summer.

1 We are starting to see those wonderful, still, autumn afternoons, with an orange sun casting long shadows, and how better to enjoy those shadows than with hedges trimmed into clean planes and curves. This is the right month for clipping evergreens. It’s the perfect job for the early part of one of those golden afternoons and a pleasure to get right. Stand back and squint: a bit more off there, level up that end and take off that wayward twig. When it’s done, you will have the perfect foil for a romantic profusion of autumn perennials.

2 The Award of Garden Merit (AGM) — the horticultural equivalent of a Michelin star — tells you that a plant is tough, reliable, floriferous, disease-resistant and, of course, attractive. You can find all AGM plants listed on the Royal Horticultural Society’s website (rhs.org.uk). The dahlia ‘Classic Rosamunde’ has received an AGM. Its foliage is a dusky purple rather than that deadly black you see on so many fashionable dahlia.

If you like the sound of it, order a plant for next spring now, because it’s not a variety you see in garden centres yet. And take a look at the National Dahlia Society’s website (dahlia-nds.co.uk), where there are many varieties for you to think about.

3 Bulbs are starting to appear for sale this month. It’s not too early to start potting them for a spring display. I get more fond of colchicums, the big autumn crocuses, because they do so well in soil that’s dark and dry in summer. Look out for corms of the superb double ‘Waterlily’. I grow Colchicum agrippinum in rough grass and am trying the vigorous ‘Lilac Wonder’ too.

4 Sorbus (mountain ash) make excellent small trees, and the berries come in many colours. Take a look in a garden centre or a public garden to see what appeals.

5 Coloured-stemmed birches, like waistcoats after a heavy meal, pop their buttons after a long growing season. The old bark peels and the fresh colour underneath becomes visible. Some remain flaky, others are shiny-smooth. Betula albosinensis var. septentrionalis AGM is a fabulous, smooth, coppery grey pink; ‘Doorenbos’ AGM is a shaggy white, but pale orange when first exposed. Nothing to stop you planting three in the same hole if you fancy the multistemmed effect.

September’s golden afternoons are the perfect time for clipping evergreens

6 Muddy autumn days make weeds grow like mad. Make sure you keep gravel parking areas clean of seedling grasses; they grow and set seed before you know it. I find that using a weed-burner eventually reduces the latent seedbank and then the surface stays generally cleaner. The muggy weather means this is the month to sow new lawns and make patch seed repairs. Patch repairs are usually needed in those abused spots where the existing grass has been stomped into submission. Aerate the old turf with a fork and prise it gently upward, before scratching the surface to make a loose seed bed.

If you prefer to leave the gardening to someone else, while you read about the subject, I would recommend Botanicum (Welcome to the Museum) by Kathy Willis and Katie Scott (Templar Publishing, £20).