Posted by Tom Steel on 29th Aug 2025

Gardening Jobs for September

As we move into September, the days may be getting shorter and cooler, but there’s still plenty to keep gardeners busy. While there may be less to do in the ornamental garden, harvest season is in full swing, and it’s also time to look ahead to next year.

Whether it’s reaping the successes of the year or planting spring-flowering bulbs for the next, September is a rewarding month for gardening. Here are our top gardening tips and jobs to help you get the most out of your garden.

What to plant in September

Refresh pots with autumn interest

Revive tired containers with cyclamen, heuchera, heather or viola for fresh seasonal colour. These plants thrive in cooler weather and will brighten up patios through autumn.

Sow hardy annuals for early summer colour

Start seeds of cerinthe, cornflower, scabiosa and ammi now to give them time to establish before winter. These hardy annuals will flower earlier and more vigorously next year than spring sowings.

Plant spring bedding for a cheerful start next year

Add wallflowers, pansies, forget-me-nots and other spring bedding to borders or pots while the soil is still warm. Early planting helps them root deeply and survive the cold months ahead.

Add late-flowering perennials for pollinators

Fill bare spots in borders with sedums, rudbeckias or asters to support bees and butterflies into the autumn. Their rich colours and nectar-rich blooms keep the garden lively as summer fades.

We have an exclusive range of J. Parker’s own perennial plants available in 1 Litre + pots. Just pop them into your beds, borders or containers and enjoy instant impact.

Garden jobs in September

Divide overgrown perennials

Perennials like phlox, daylilies and astrantia can become congested - lift and divide them to encourage fresh growth and prolong their life. It’s also a great way to fill gaps or share plants with friends.

Tip: Replant divisions promptly and water well to help them establish.

Take cuttings from tender plants

Propagate favourites like salvias, pelargoniums and fuchsias now to overwinter indoors. Cuttings taken while it's still warm will root quickly and be ready for potting up in spring.

Tip: Choose non-flowering shoots and remove lower leaves for best results.

Prune trained apple and pear trees

Give cordons, espaliers and fan-trained fruit trees a final trim - shorten side shoots to maintain structure and encourage fruit bud development. This keeps trees compact and productive.

Tip: Always use clean, sharp tools to reduce the risk of disease.

Lift and store tender bulbs

Gladioli, begonias and other tender bulbs should be lifted before frost arrives. Let them dry out completely before storing in a cool, frost-free place.

Tip: Brush off excess soil, but avoid washing bulbs to prevent rot.

Apply vine weevil control in pots

Now’s the time to target vine weevil grubs, which can devastate potted plants over winter. Use biological controls like nematodes or apply a suitable insecticide.

Tip: Check for notched leaf edges - an early sign of adult vine weevils.

Collect and store seeds from garden favourites

Harvest mature seed from plants like nigella, aquilegia and calendula to save for next year’s sowing. Make sure they’re fully dry before sealing them in labelled paper envelopes.

Tip: Store seeds somewhere cool, dry and mouse-proof to maintain viability.

Tidy hedges and reshape topiary

Trim hedges and clipped evergreens like box and yew before growth slows. This keeps them looking crisp through autumn and into winter.

Tip: Avoid cutting into old wood - many evergreens won’t regrow from it.

Clean up borders and remove spent foliage

Cut back faded perennials, clear fallen leaves, and tidy up tired borders. This helps reduce overwintering pests and disease while keeping the garden looking smart.

Tip: Leave some seed heads for wildlife and winter interest where possible.

What vegetables to plant in September

Kale

Variety to try: Kale Borecole Vates Blue Curled is a cold-hardy, compact variety with finely curled blue-green leaves. Ideal for autumn sowing, it stands up well to frost and offers nutritious pickings into winter.
Growing tips: Sow seeds thinly in well-drained, fertile soil in full sun or partial shade. Thin seedlings to about 20 cm apart to give plants space to develop. Water regularly and consider netting young plants to protect from pests.
Harvesting: Begin picking outer leaves once plants are well established, around 8-10 weeks after sowing. Regular harvesting encourages continued growth, and the flavour improves after the first frosts.

Pak Choi

Variety to try: Pak Choi Red F1 is a striking variety with deep red-purple leaves and green stems. It’s fast-growing and performs well in cooler temperatures, making it ideal for a September sowing.
Growing tips: Sow seeds directly in fertile, moist soil or containers, spacing them about 20-25 cm apart. Keep soil consistently damp and provide some shade in warmer weather to prevent bolting.
Harvesting: Harvest young leaves after 3-4 weeks for salads, or wait 6-8 weeks for mature heads. You can cut whole plants at the base or pick a few outer leaves to allow regrowth.

Lettuce

Variety to try: Lettuce All Year Round is a reliable butterhead variety that lives up to its name - perfect for September sowing under cloches or in a greenhouse for a late crop.
Growing tips: Sow seeds sparingly in rows or containers filled with well-drained compost. Place in full sun or light shade and keep the soil evenly moist. Thin seedlings to around 15-20 cm apart to allow heads to develop.
Harvesting: Pick outer leaves when they reach a usable size, or wait for full heads to mature. Harvest regularly to prolong cropping and prevent plants from going to seed.

Flowers to plant in September

Cyclamen hederifolium

Heuchera Palace Purple

Iris Louisiana Heather Stream

Plants that flower in September

Aster novi-belgii Blue

Hydrangea paniculata Unique

Sedum kamtschaticum Variegatum

Growing Guides for September

Achillea | Heuchera | Hydrangea | Rudbeckia | Scabiosa

September is a wonderful time to enjoy the fruits of your labour and prepare for a prosperous spring next year. With these jobs and planting tips, your garden will stay vibrant and healthy through the seasons. Happy gardening!

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