10 Garden Jobs to Do in September for a Better Autumn and Spring

I’m a fairly novice gardener, so I find these monthly garden job lists genuinely useful. Otherwise, I’m quite capable of wandering around with my secateurs cutting things I shouldn’t be cutting, while completely ignoring the jobs I actually need to do.

September is particularly confusing because the garden hasn’t quite finished with summer yet. My own garden is still giving me plenty of obvious signs of life, but there are also leaves beginning to drop, flowers going over and that definite feeling that autumn is on its way.

So, after a bit of research — and taking some fairly obvious hints from what’s happening in my own garden — I’ve put together a list of 10 September garden jobs worth getting done this month.

The good news is that September isn’t about ripping everything out and putting the garden to bed. Quite the opposite. There are jobs that will keep it looking good for longer this year while quietly setting things up for a much better spring.

Here are the ten on my list.

1. Keep Deadheading Anything That’s Still Flowering

I’m starting with the easiest job because this is one I’m already doing.

Don’t give up on your summer flowers just because September has arrived.

Dahlias, roses, penstemons and plenty of bedding plants can continue flowering well into autumn if the weather behaves. Removing faded flowers stops many plants putting their energy into producing seed and encourages them to keep producing more blooms instead.

Hanging baskets and pots can also have more life left in them than you might think. Keep deadheading, water when they need it and give flowering containers a feed if they’re still performing.

There’s plenty of time for pumpkins and bare branches later. I’m keeping the flowers for as long as they’ll have me. The RHS also recommends continuing to deadhead plants including dahlias, roses and penstemons during September to prolong their display.

2. Plant Your Spring Bulbs – But Leave the Tulips Alone for Now

This is probably the September job with the biggest delayed reward.

Spring-flowering bulbs start appearing everywhere at this time of year, and now is a good time to get daffodils, crocuses and hyacinths into the ground.

As a general rule, bulbs are planted at around two to three times their own depth, with the pointed end facing upwards. Planting several together rather than dotting individual bulbs around also tends to create a much better display.

One useful thing I discovered: you don’t need to plant your tulips yet.

Tulips are generally better planted later, around November, while daffodils, crocuses and hyacinths are worth getting underway during early autumn.

So if you’ve gone slightly mad buying packets of bulbs, don’t feel as though the whole lot needs to be planted this weekend.

3. Give Your Lawn Some Attention

By September, my lawn tends to reveal exactly what summer has done to it.

There are worn patches where we’ve walked repeatedly, areas that have gone slightly brown and bits where the grass isn’t nearly as lush as it was in spring.

Fortunately, early autumn is an excellent time to do something about it.

Continue mowing while the grass is growing, but start keeping the blades a little higher. Depending on where you live and the condition of your lawn, September is also the beginning of autumn lawn-care season.

That can include scarifying to remove thatch, aerating compacted ground and repairing bare patches with grass seed or turf.

You don’t necessarily need to do every lawn job every year. Look at what your grass actually needs rather than attacking it with every garden tool you own.

September and October are particularly useful months for lawn repairs because mild, damper conditions help grass recover before winter.

4. Divide Perennials That Have Become Too Big

This sounded considerably more intimidating before I realised that “dividing perennials” essentially means digging up an established clump, splitting it and replanting the sections.

And you get more plants for free.

I’m listening.

September is a good time to divide established herbaceous perennials that have become overcrowded or aren’t flowering as well as they used to. Hardy geraniums and heleniums are among the plants that can benefit from being divided at this time of year.

Water the plants afterwards while they establish.

If you’re still filling gaps in your borders, this is also quite a satisfying way of doing it without going back to the garden centre and somehow spending another £80.

5. Don’t Cut Everything Back

This is possibly the most useful thing I’ve learned while looking at what to do in September.

The garden doesn’t need to be completely tidied.

There’s a temptation once plants start going over to march around cutting everything to ground level. But many perennial stems and seedheads can stay in place through autumn and winter.

They provide structure when the rest of the garden becomes bare, can offer food and shelter for wildlife and, when there’s a frost, some of them look genuinely beautiful.

The exception is anything that’s collapsed into a soggy mess or is obviously diseased. That can be cleared away.

Otherwise, put the secateurs down occasionally.

Leaving healthy perennial growth until later in winter can be better for wildlife and saves us a job in September anyway.

6. Take Cuttings From Plants You Want Again Next Year

This is another job that feels surprisingly clever once you start doing it.

If you’ve got tender plants that you’ve particularly loved this summer, September gives you an opportunity to make more of them before colder weather arrives.

Pelargoniums and osteospermums are two good examples.

Take healthy non-flowering shoots, remove the lower leaves and pot the cuttings into suitable compost. Keep them somewhere light and protected while they establish.

Even without a greenhouse, a bright windowsill can work for some tender cuttings.

Essentially, you’re getting a head start on next year’s garden using plants you’ve already paid for.

Which, given the amount of money it’s possible to spend on plants every spring, feels like something I should have discovered years ago.

7. Harvest What’s Ready – And Don’t Forget the Potatoes

If you grow fruit or vegetables, September can be one of the most satisfying months of the year.

Apples and pears are coming into their own, along with autumn raspberries and other late crops. Potatoes that are ready for lifting shouldn’t be forgotten either, particularly as leaving them in the ground too long can increase the chance of slug damage.

There’s still time to grow things too.

Depending on your space and what you enjoy eating, September can be used for sowing overwintering salads such as spinach, winter lettuce and rocket, while overwintering onion sets can also go in.

So the vegetable patch isn’t finished simply because summer is.

8. Plant New Perennials While the Soil Is Still Warm

September is actually a lovely planting month.

The intense heat and dry spells of summer are hopefully easing, rainfall tends to become more reliable, but the soil still retains warmth.

That combination gives new plants an opportunity to establish their roots before winter.

Later September can be particularly good for planting hardy perennials, so if there are obvious gaps in your borders, now is worth considering rather than automatically waiting until next spring.

You’ll still need to keep newly planted additions watered during dry periods. Autumn doesn’t mean we can completely abandon the watering can just yet.

This is also a useful time to stand back and look at the garden properly.

Where did you have a massive gap this summer? Which border desperately needed more height? Where was everything green and nothing flowering?

I’m trying to get better at fixing those problems while I can still remember them.

9. Clean Out the Greenhouse Before It Fills Up Again

If you have a greenhouse, September is the time to give it some attention before tender plants start moving back inside.

Clear away dead plant material, clean pots and staging, remove weeds and give the glass and structure a proper clean.

Check for damaged panes, clips or anything else that’s going to become considerably more annoying once the weather turns.

It’s also worth checking plants carefully for pests before bringing them indoors. The last thing you want is to provide vine weevils, scale insects or other unwanted guests with luxury winter accommodation.

As light levels begin dropping, greenhouse shading can also start coming down.

It’s one of those jobs that’s extremely easy to postpone until November, when it’s freezing and you deeply regret not doing it in September.

10. Get Ready for the Leaves – But Don’t Become Obsessed With Tidying

They’re coming.

If you have deciduous trees nearby, September is your warning that the annual leaf situation is about to begin.

One job worth doing now is netting ponds before heavy leaf fall gets underway, which can save you fishing decomposing leaves out of the water later.

But again, autumn gardening doesn’t need to mean removing every fallen leaf from sight.

Leaves lying thickly across lawns or paths may need clearing, but elsewhere they can provide useful habitat for insects and other wildlife. Collected leaves can also be turned into leaf mould rather than simply being thrown away.

I quite like the idea of becoming slightly less tidy with the garden as autumn arrives.

Not abandoned.

Just less obsessed with making nature look as though somebody has vacuumed it.

What Should You Prioritise in the Garden in September?

If you’re looking at this list thinking there’s absolutely no chance you’re doing all ten, neither am I suggesting you spend every weekend in gardening gloves.

For me, the priorities are fairly straightforward:

Keep what’s currently flowering going, plant for next spring and deal with anything that will become a bigger problem if I ignore it.

That means deadheading takes a few minutes whenever I’m outside. Bulbs can be planted gradually. The lawn can have some attention when the weather is right, and the more serious autumn clearing can wait.

September is really a crossover month.

We’re not shutting the garden down for winter yet. In fact, there can still be weeks of colour ahead. But a few sensible jobs now should make the transition into autumn considerably easier — and hopefully mean that when the first daffodils appear next year, I’ll be extremely pleased with September me.

And possibly slightly surprised that I remembered to plant them at all.

Joanne Brook-Smith is a writer and editor with two decades of publishing experience. She launched Crave Magazine during the Covid period to create a fresh, inspiring space for food, travel and lifestyle content.