10 Essential Gardening Jobs to Do in September

1. Give Your Lawn Some Autumn Attention

After a summer of mowing, dry spells and heavy use, September is an excellent time to give your lawn some attention.

Continue mowing while the grass is actively growing, but gradually raise the cutting height. Cutting the lawn too short as temperatures fall can put unnecessary stress on the grass.

September is also a good time to scarify your lawn if there is a build-up of moss or thatch. You can also aerate compacted areas with a garden fork or aerator to improve drainage and allow oxygen to reach the roots.

Bare or damaged patches can be reseeded while the soil is still relatively warm.

Gardeners Guide tip: Autumn lawn feeds are generally higher in potassium and lower in nitrogen than spring feeds. Avoid encouraging lots of soft new growth just as colder weather arrives.

2. Plant Spring-Flowering Bulbs

It might seem early to start thinking about spring, but September is the perfect time to get many spring-flowering bulbs into the ground.

Popular choices include:

• Daffodils
• Crocuses
• Hyacinths
• Alliums
• Snowdrops
• Muscari

As a general rule, plant bulbs at around two to three times their own depth, with the pointed end facing upwards.

Bulbs also work brilliantly in pots. Layering different varieties at different depths can create a container that produces flowers over a much longer period.

Tulips are often better planted a little later in autumn when the soil has cooled.

3. Keep Deadheading Flowers

Don’t give up on your summer displays just yet.

Regularly removing faded flowers from plants such as dahlias, roses and many bedding plants can encourage them to keep flowering well into September and sometimes beyond.

Rather than simply pulling off the dead petals, remove the complete spent flower back to a healthy leaf or bud where appropriate.

Keep watering containers too. Cooler weather doesn’t necessarily mean pots have enough moisture, particularly during dry or windy spells.

4. Divide Overcrowded Perennials

September is a useful time to divide many established herbaceous perennials.

If a plant has become overcrowded, is producing fewer flowers or has developed a bare centre, division can help rejuvenate it.

Lift the plant carefully, split the root mass into several healthy sections and replant them around the garden.

It’s effectively free plants, while also improving the health of the original clump.

Water newly divided plants thoroughly and keep an eye on them during dry September weather while they establish.

5. Collect Seeds for Next Year

Before cutting everything back, take a look around the garden for mature seed heads.

Seeds can be collected from many garden favourites and stored for sowing next year.

Choose seeds from healthy plants and collect them on a dry day. Allow them to dry thoroughly before storing them in labelled paper envelopes somewhere cool and dry.

Remember that seeds collected from hybrid varieties won’t necessarily produce plants identical to their parents—but that’s sometimes part of the fun.

6. Harvest Fruit and Vegetables

September can be one of the busiest months in the vegetable garden.

Depending on what you’ve planted, you may still be harvesting:

• Tomatoes
• Courgettes
• Runner beans
• French beans
• Potatoes
• Beetroot
• Carrots
• Apples
• Pears
• Plums
• Autumn raspberries

Harvest beans and courgettes regularly to encourage continued production.

If outdoor tomatoes are struggling to ripen as temperatures fall, remove some excess foliage around the fruit to improve light and airflow.

Keep an eye on the weather later in the month, particularly if you’re gardening in Scotland or another cooler part of the UK.

7. Start Clearing Fallen Leaves

The first significant leaf fall often begins during September.

You don’t need to obsessively remove every leaf from the garden. Fallen leaves are an important part of the garden ecosystem and can provide shelter for insects and other wildlife.

However, thick layers shouldn’t be left sitting on lawns for long periods because they can block light and encourage unhealthy conditions underneath.

Collect leaves from lawns, paths and patios and consider turning them into leaf mould.

Pile damp leaves into a leaf-mould cage or suitable bags with ventilation holes and allow nature to do the work. Given enough time, they’ll break down into an excellent soil conditioner.

8. Tidy Borders – But Don’t Overdo It

It’s tempting to completely strip the garden back once plants start fading, but a perfectly tidy garden isn’t always the best garden.

Remove diseased or badly damaged material and cut back plants that have collapsed or become messy.

However, consider leaving attractive seed heads and some healthy stems standing over winter.

They can provide food and shelter for wildlife while also adding structure to an otherwise bare winter garden.

9. Plant Trees and Shrubs

Autumn is one of the best planting seasons of the year.

The soil retains warmth from summer while becoming naturally wetter as we move into autumn. This gives newly planted trees and shrubs an opportunity to establish roots without having to support masses of new top growth.

Dig a generous planting hole, position the plant at the correct depth, backfill carefully and water thoroughly.

Don’t assume autumn rain will do all the work. Newly planted trees and shrubs may still need watering during dry periods.

10. Start Preparing for Colder Weather

September weather can be wonderfully mild one week and surprisingly chilly the next.

Use this month to start preparing more tender plants before the first frosts arrive.

Check which container plants will need moving somewhere sheltered and inspect your greenhouse before winter. Clean dirty glass, remove diseased plant material and check for damaged panes or gaps.

If you have particularly tender plants, it’s also worth making sure you have horticultural fleece or other winter protection ready rather than discovering you need it on the first freezing night.

Don’t Write the Garden Off in September

September isn’t the end of the gardening year. In many ways, it’s the beginning of the next one.

The soil is warm, autumn rain is arriving and there’s plenty that can still be planted, harvested and improved.

Spend a few weekends looking after your lawn, planting bulbs, dividing perennials and preparing for colder weather, and you’ll not only have a tidier garden this autumn—you’ll be setting yourself up for a much better display next spring.

Gardeners Guide — Grow Better. Garden Smarter.