During September, animals such as hedgehogs and bats are still busy feeding up before hibernation. Summer visitors, like swallows and willow warblers, will be heading off to Africa and many mated bumblebee queens are already hibernating underground. Peacock and small tortoiseshell butterflies take refuge in sheds and garages where they will shelter over winter.

From this month there are different moths on the wing too, as summer species make way for autumn-flying moths like the feathered thorn and the Merveille du Jour. If you’re lucky, you might see hummingbird hawk-moths out and about during the day, feeding on red valerian flowers before returning south.

More wildlife gardening advice:

Plants for wildlife

Honeybee on ‘Peach Brandy’ dahlia

Allium bulbs

September is the ideal time to plant allium bulbs for a display of nectar-rich flowers next spring and summer. With their spherical flowerheads comprising many tiny florets, alliums provide a superb food source for bumblebees, solitary bees and other pollinators. These versatile plants add structure when planted in drifts and look wonderful in cottage gardens, wildlife borders and prairie-style planting schemes. If you choose varieties that flower successionally, you can have alliums in bloom from May right through to August.

A. hollandicum ‘Purple Sensation’ is a popular variety, and rightly so. It has splendid purple spherical flowerheads from May to June and is a favourite in our garden with the bees. A. siculum is an unusual-looking allium that grows well in shade and self-sows around the garden. Its beautiful greenish white flowers with pinky-red stripes nod delicately from the stem like arms in a candelabra. Beloved by bumblebees, this elegant allium flowers in May and June. To extend the season, we plant A. sphaerocephalon or the drumstick allium as border edging. Flowering from July to August, its attractive blackcurrant-coloured flowerheads are a magnet for bees and butterflies.

We let our perennial Welsh onion (A. fistulosum) flower, to provide extra nectar for pollinators. You could also leave a few leeks (A. ampeloprasum) in the ground. We use chives (Allium schoenoprasum) to edge our vegetable beds. If you don’t have space in the ground, they are easily grown in pots. Siting a container planted with herbs such as rosemary, thyme and chives in a sunny spot on the patio provides flavouring for the kitchen and a feast for pollinators, too.

Plant allium bulbs in a sheltered sunny spot, in free-draining soil at a depth at least four times the diameter of the bulb. In areas with heavier soil, add plenty of grit to the bottom of the planting hole to improve drainage or plant in deep containers in a peat-free multi-purpose compost.

Annual flowers

Sow annual flowers now to provide for pollinators next spring and summer. Autumn-sown plants will bloom a couple of weeks earlier than spring-sown annuals, extending the season for insects. Choose nectar-rich plants such as cornflowers, scabious, honeywort, love-in-a-mist and pot marigold. Avoid growing double-flowered varieties as they may contain little or no pollen or nectar.

Either broadcast sow by scattering seed over well-prepared soil that has been weeded and raked, or sow in drills. Alternatively, seeds can be sown now undercover, overwintered in a cold frame or greenhouse, and planted out next spring.

Deadhead for more blooms

Keep the nectar flowing by deadheading spent blooms to encourage the production of more flowers. Plants that benefit from regular deadheading include hebes, buddleja, cosmos and dahlias. Leave seedheads to mature on plants like sunflowers, Verbena bonariensis, teasel, echinacea and ice plants, and let roses like R. canina and R. rugosa develop hips to provide food for birds later in the autumn and throughout the winter.

Thrifty tip

Autumn is a good time to divide wildlife-friendly summer-flowering perennials to reinvigorate your stock and provide free plants for next year. If the month is particularly wet, wait until later in the autumn or postpone until next spring. Astrantia, heuchera, clump-forming iris such as I. sibirica and hardy geraniums can all be divided this month.

Lavender is usually cut back after flowering to prolong the life of the plants, but if you forget – don’t worry. We’ve started leaving seedheads on a few lavender plants, as they bring in the goldfinches later in the year.

Feeding wildlife

Rowan berries are an important food source for birds in autumn

• Birds and mammals are out foraging in our gardens and hedgerows for fruit and nuts. Native hedging offers a bounty of ripening hawthorn, rowan and honeysuckle berries, rose hips, hazelnuts and blackberries this month. Hedges provide shelter for wildlife too and create corridors between other habitats. If you have room for a new hedge, now is a good time to order bare-rooted plants to be delivered later in the autumn or during the winter for planting. Discover the best hedges for wildlife.
• Leave good quality meaty hedgehog food, meaty cat food or cat biscuits to help hedgehogs build up sufficient weight before hibernation in a few weeks’ time. Don’t forget to leave water out for your hoggy garden visitors, too.

Growing Greener

It’s worth considering whether the bulbs and plants that you buy might have been treated with pesticides. Try to avoid bringing neonicotinoids and other pesticide residues into the garden and support pesticide-free growers by sourcing new plants carefully. Check with nurseries and garden centres before you buy.

Look out for logos like the Saving Pollinators Assurance Scheme, run by the National Botanic Garden of Wales, which requires that plants are proven to support pollinators and grown without the use of synthetic insecticides or peat. The RHS also has a list of nurseries that grow some or all of their plants using organic principles.

Creating and maintaining habitats

September is a good time to clean bird boxes

• Clean out bird boxes in the next few weeks, making sure first that birds have finished nesting. Boxes will then be free of parasites and fleas if birds choose to roost in them once the weather turns colder. Remove the contents of the nest box with a dustpan and brush and check that the box is in good repair. If there are any eggs, these may legally be removed any time between September and January, provided the nest is not still in use. They must then be disposed of. Clean the inside thoroughly with boiling water, leave until completely dry and replace the nest box. Avoid using any kind of insecticide or any other chemicals. Find out more about cleaning bird boxes.
• Mow summer meadows at the beginning of September, walking through the wild flowers and long grass first to check for and disperse any sheltering animals such as frogs, crickets and hedgehogs. Leave mowings on the ground for a few days for any seeds to drop before composting. Watch Monty mowing his meadow.
• Avoid cutting back herbaceous perennials and clearing borders this month so that stems and foliage provide shelter for overwintering insects. You’ll also benefit from architectural forms giving structure to the borders overwinter. Grasses like Miscanthus sinensis and herbaceous perennials such as globe thistle and echinacea look particularly fine in winter, laced with early morning frost. Plants can then be cut back in late winter or early spring.
• Clear excess mud and dead leaves out of ponds now that there are no tadpoles left and frogs won’t yet be overwintering in the mud and vegetation. Leave the material you remove on the edge for a few days to let any creatures return to the pond before you add it to the compost.

Look out for… arachnids

Spider in web

There’s something magical about walking through the garden early on a September morning when hedges and flowerbeds are laced with cobwebs, hung with dew, each with a garden spider in attendance. And these conspicuous web-spinners are not the only arachnids you could see outside your back door this month…

• The most common of the orb web spiders, the garden spider (Araneus diadematus), can be identified by the central cross-like marking of white spots which gives it one of its other names – the cross spider. Look out for this arachnid on spiral webs strung across window frames, walls and hedges, waiting for flying insects to become ensnared. At 10-18mm, the females are one of the largest UK spiders and are easily spotted, but the males are tiny, only half the size of females at around 4-8mm.
• Easily identified by the black and white striped patterns that give them their name, Zebra spiders (Salticus scenicus) have two large eyes at the front of the head that can swivel and focus, giving them superb binocular vision, and six smaller eyes further round. They hunt on trees, walls and fences, often jumping onto their prey from several centimetres away. Always an impressive feat to watch, given that these tiny spiders are only around 7mm in length!
• Harvestmen (Phalangium opilio) are actually spider lookalikes. They belong to a closely related group of arachnids called the Opilones. They can often be seen in summer and early autumn hunting in vegetation in the garden or around the house. Unlike spiders, they don’t have a venomous bite. Instead these long-legged invertebrates catch small insects using hooks on the ends of their legs.

Get to know some of the UK’s colourful arachnid inhabitants, in our comprehensive guide to spiders.

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