What to do in the garden in SEptember


While the summer heat can linger on into September, this is generally a cooler month than August, with stronger winds and shorter gardening days. Harvesting will take up a lot of your time this month, but there’s plenty more to be done! To help guide you through this month, here are the key gardening jobs you need to be tackling during September.

Trees and shrubs

There’s plenty of pruning to be done in September, with late flowering shrubs such as the rock rose in need of your attention, along with climbing and rambling roses - although wait until you’re sure they’ve finished flowering before breaking out the secateurs. 

Conditions are likely to be reasonably dry quite late into the month, so make sure that you keep your rhododendrons and camellias watered, which will help to ensure that the spring buds will develop well. It’s also the ideal time to start ordering new trees and shrubs, for planting before the autumn rains arrive. 

Perennials, biennials and annuals

Although summer is coming to an end, it’s important to continue to maintain your container and hanging basket plants, as with proper care these can carry on thriving until late in the autumn. Dead-heading penstemons, dahlias and roses can also prolong their flowering.

September is a good time to plant new perennials, thanks to the combination of warm soil and increased rain fall. It’s also an opportunity for you plant any biennial plants that you haven’t got round to yet. And as there may be a few gaps in your borders, you can fill them with autumn flowering species such as chrysanthemums, while planting amaryllis or hyacinth bulbs for forcing will guarantee you a pleasing crop of blooms in time for Christmas. 

Vegetables and fruit

September is all about harvesting and ensuring that late-harvest crops are progressing. Continue to pick fruits such as blackberries, plums and apples. If you have more than you need, they can be stored effectively by washing, stoning where necessary and freezing. And make sure you keep the grass under your fruit trees short, so you can identify windfall crops.

A useful tip when harvesting potatoes at this time of year is to prune the foliage at ground level two to three weeks before you harvest, which can prevent potato blight and may also help to toughen the tubers’ skins. When harvested, spread potatoes out to dry before storing in a cool, dark place. Make sure you check the crop thoroughly and throw out any damaged or diseased potatoes as these can ruin the whole lot. 

And if you want to make sure that your pumpkins are ready for Halloween, remove any leaves that might be shading the fruits to maximise ripening. It’s also a good idea to lift pumpkins off the wet soil by resting them on a piece of stone or wood, to prevent rotting. 

Besides the harvesting, this is a good time to get started on the autumn tidying. Clear away any exhausted crops and carry out a thorough weeding to make sure this part of the garden is clean and tidy. Beans and peas can be cut away at ground level, to leave the roots in the ground where they perform an important role in fixing and releasing nitrogen in the soil. 

Brassicas should be netted to protect them from the birds and make sure you pick off rotting fruits on pear, plum or apple trees. If you have a wall-trained peach tree, it should be covered to help prevent peach leaf curl. And don’t forget to cut back dead raspberry canes. 

There is still a good deal of planting that you can do in September. Rooted strawberry runners can be planted out, along with garlic bulbs and onion sets. It’s a good time also to pot up mint and parsley which will serve you throughout the winter, and remember to order your berries and currant bushes as these are best planted at this time of year. 

Lawn Care

September is an important lawn maintenance month. Aerate your lawn with a garden fork, which will help to prevent compaction, and at the same time you can clear the surface with a rake and attend to any worn or dead patches. When your maintenance work is complete, it’s a good idea to apply lawn top dressings and fertilisers, as well as biological measures to deal with lawn chafer damage. 

Other bits and bobs

There’s plenty to do in the greenhouse during September. Start with a general clear out, removing decaying plant material that could be a home to pests and parasites. Watering should be done early in the day so that the greenhouse isn’t damp in the evening, as cool, damp nights can lead to botrytis taking hold. And to maximise the warmth in your greenhouse, close vents and doors late in the afternoon to trap heat. 

This is also a good month to consider soil maintenance. Sow crops such as mustard or rye grass on fallow areas, which will help to make the soil richer and control winter weeds. 

You can plan for the upcoming leaf fall by setting up compost bins, but remember not to compost diseased plant material as this may contain fungal spores or infections that could be passed on to your plants. And if you’ve been considering setting up a water butt to collect rain water, September is the ideal month to install it. 

Planning ahead

As the summer draws to a close, September offers you the opportunity to take stock of what worked and what didn’t during the year. Think about what changes you would like to make, and do your research to make sure any problems and issues don’t recur. 

It’s also a good time of year to start planning for the spring. Make sketches of your garden layout for the following year so you can decide what crops, seeds or rootstock you need to purchase. And don’t forget to order your spring bulbs for autumn planting.


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