Flowers and bulbs to plant in September – Guide from garden design experts
Spring bulbs are the obvious start. But September also suits hardy annuals, which will flower next summer if sown now rather than in spring.
Bulbs for spring colour
Plant daffodil bulbs from mid-September, well ahead of tulips, which prefer the colder soil of November.
Set them at a depth of roughly three times their own height. Firm soil around the roots so they don’t sit in an air pocket.
Crocus and other spring-flowering bulbs follow the same rule. Earlier is better, since they need time to root before the ground turns cold.
Hardy annuals for a cut flower garden
If you want armfuls of flowers next June rather than a modest July show, sow calendula and other hardy annuals now.
Calendula, with its deep orange petals, is an easy starting point among flowers to sow this time of year. It draws bees and butterflies through summer.
It’ll bloom by early summer, well ahead of anything you start in spring.
A cut flower garden built around a September sowing gives plants a real head start over anything sown the following spring.
We often include hardy annuals like these in the planting schemes we design for cottage-style gardens.
Ornamental favourites for cottage colour
Poppy and ammi majus, also known as bishop’s flower, add height and movement to a border without much fuss.
Sow the seeds direct where they’re to flower, since both dislike being transplanted.
Both self-seed readily, and a September sowing often means new flowers will appear in gaps for years afterwards.
Mix in a few white flowers alongside brighter purple flowers so borders read well from a distance as well as close up.
Vegetables and salad crops to sow in September
Most of the summer harvest is winding down by September, but the veg garden doesn’t need to go quiet.
There’s a solid list of vegetables to grow in September, once the summer crowd has cleared out of the beds.
Salad leaves and quick crops
Lettuce and other salad leaves do well from a September sowing, especially hardier winter varieties that shrug off a dip in temperature.
Radish is about as forgiving as vegetables get.
Sow radish seeds direct into garden soil in full sun or a partially shaded spot, and keep the soil consistently moist. You’ll often be pulling radishes within a month.
Direct sow spinach in September and it crops right through into winter, especially once you cover with fleece as the first frosts threaten.
Alliums and roots for next summer
Onion sets planted now establish roots before winter sets in, giving a noticeably earlier harvest next summer than a spring planting would.
Sow turnips now and they’ll overwinter in the ground, giving you an early harvest often before most spring-sown vegetables have even germinated.
Giving young crops the best start
Well-drained soil matters more in autumn than in summer, since waterlogged roots rarely survive a Scottish winter.
Raised beds or a cold frame give young seedlings a better chance if your beds tend to hold water.
A cold frame or unheated greenhouse is worth it if you’re serious about extending the season.
Water well after sowing, then keep well watered until seedlings are established and the autumn rain takes over.
Net anything from the brassica family to keep pigeons off.
Herbs and strawberry runners
Parsley and coriander both cope with a September sowing if kept somewhere sheltered. That makes them a good fit for even a small kitchen garden or a few pots by the back door.
A cold frame or windowsill suits them better than open ground this late in the year.
It’s also worth planting strawberry runners now, since they’ll establish roots before winter and fruit properly next summer rather than their first year.
Trees and shrubs to plant in September
September through into winter is the best stretch for planting trees and shrubs across most of September in the UK.
Central Scotland’s window closes a little sooner than further south.
Trees planted now still spend the colder months building roots while the top growth stays dormant.
Why autumn planting works
By the time spring arrives, autumn-planted trees are already established, giving you established plants next year rather than saplings still finding their roots.
Evergreen trees and shrubs benefit most from an early September start, since they don’t lose their foliage and keep drawing moisture right through winter.
Bare-root planting and aftercare
Plant bare-root trees while they’re dormant, sold without a pot of compost around the roots.
They offer better value and are often healthier than container-grown alternatives, but get them in the ground quickly, or the exposed roots dry out.
Fill any gaps in your borders now rather than waiting for spring.
Mulch around the base of new planting to lock in moisture while the roots settle.
Our certified arborists can advise on species suited to your soil and aspect, and care for your grass through maintenance and scarifying.
Our landscape designers build planting schemes that still look right in ten years, well beyond next spring.
Why September works for planting
Soil biology stays active well into autumn, long after the top growth of most plants has stopped.
Worms keep working while the ground stays workable, breaking down mulch and compost into nutrients roots can use by spring.
Warm soil, cooler air
Sow seeds in September and they get a head start spring sowings can’t match. They spend autumn growing roots while spring-sown plants are still waiting for the soil to warm up.
Seeds sown now often germinate within days rather than the weeks a cold spring soil demands.
Perennials and borders that establish before spring
Perennials in September, once planted, settle in over autumn and winter.
Come the first warm spell in spring, they put on strong growth instead of starting from a small seedling.
A single specimen shrub or an entire border benefits from the same approach.
Choose a sunny, sheltered spot where you can, and water in thoroughly after planting.
Resist the urge to feed anything until spring, since new roots need time to establish before they can use extra nutrients.
General September gardening tips
A quick pest check is worth building into any gardener’s routine through spring and summer as well as September.
Check emerging seedlings for pests and diseases in the first few days after planting, when they’re at their most vulnerable.
Slugs are especially active after autumn rain, so a late-evening check of new plants pays off more in September than any other month.
Jot down plants to grow next year while this year’s results are still fresh.
Common questions about planting in September
Is it too late to plant in September?
No. For bulbs, trees, shrubs and hardy vegetables, September is closer to ideal than late in the season. Even sowings made at the end of September still have time to establish before the first hard frost.
The vegetables that run out of time are tender summer crops like courgettes and beans. They need a full growing season ahead of them to reach harvest, not just a few weeks before the first frost.
What’s the best thing to plant in September?
Daffodil bulbs are the easiest win if you want guaranteed spring colour with almost no effort. Bare-root trees and shrubs make better use of the whole autumn and winter window, but they’re a bigger commitment than a bag of bulbs.
What vegetables can I plant in September and October?
The list of vegetables to plant in September runs longer than a quick glance suggests. Garlic and onion sets, winter lettuce, spinach, turnips and radishes all cope well with a September or early October sowing. Garlic in particular wants a spell of cold weather to form proper cloves, so an autumn planting suits it better than spring.
Get your garden ready for the season ahead with GGM Landscaping
Getting started early in September pays off, no matter the size of the project.
A cottage garden built around the hardy annuals and cut flowers above benefits from proper garden design and planting scheme expertise. The same goes for any bigger border rework.
Keep your garden productive through the shorter days by planning now, rather than waiting until the ground turns too cold to work.
We design, build and maintain gardens across Glasgow and Central Scotland, from a single bed of spring bulbs to a full garden makeover.
Get your free garden consultation and we’ll help you plan a planting scheme that earns its keep well beyond this September by calling us on 07946 322717.