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September in the garden

Autumn garden

Your garden in September

As summer comes to a close (we’ve still got our fingers crossed for a bit of late sunshine) and we start to transition into autumn – while we’re looking forward to cosy knits, crunchy leaves and pumpkin spice lattes – there’s still plenty to be done in the garden in September.

September in the garden is all about preparing for the changing season and keeping your garden a vibrant and healthy outdoor space. Keep a close eye on the weather forecast looking out for early frosts, particularly towards the end of the month.

We’ve put together a list of garden jobs for September for you to make the most of this transitional period!

Harvesting apples - gardening jobs for September

Harvesting in September


September is an exciting time in the garden or allotment for harvesting the rewards of your hard work. Here are some crops to harvest in September:

  • Harvest onions after the leaves begin to turn yellow. Gently lift the onion bulbs and keep in a dark, dry, warm spot.
  • You can pick autumn raspberries right up until the first frost.
  • Cooking a crumble? Ripe and ready to pick apples will come away from the branch with a small twist. If you’re having to tug, the apple isn’t ready to be picked yet.
  • If they haven’t already, tomatoes should ripen this month. Snip back foliage to help the sun reach the fruits more easily. If tomatoes haven’t ripened before the temperature starts to drop, cut off stems of unripe tomatoes and ripen indoors.
  • Harvest your maincrop potatoes when the foliage turns yellow. They’ll likely be ready from August to September.
  • Harvest your herbs before winter and freeze ready to add to meals.
Trim lavender in August

Pruning trimming and deadheading


Summer flowering blooms will be fading and dying back so September is a big month for pruning and tidying in the garden. Snips at the ready, here’s your jobs:

  • Prune back summer-flowering shrubs and perennials to promote growth and shape. It’s also good to cut back dead stems and foliage to avoid encouraging any fungal diseases.
  • Continue to deadhead spent flowers to encourage further blooms.
  • Cut back lavender and rosemary before the temperature drops but avoid cutting back into old wood as this can damage the plant.
September lawn care

Law care in September


If you want a lush, green lawn throughout the year, there’s a few jobs to be done in September, including:

  • Continue mowing the lawn but reduce the frequency and begin to raise the cutting height slightly to protect the grass from coming frosts.
  • Aerating the lawn, especially in any areas that are particularly compacted to improve drainage and encourage healthy root growth. It’ll also allow the nutrients to better reach the roots.


  • Apply autumn lawn feed rich in potassium and phosphorus to strengthen the grass before winter. Avoid summer lawn feed that encourages fast growth which would be susceptible to disease as the temperature drops.
  • Beginning raking and spiking early to avoid build-up of debris on your lawn and reduce the risk of water logging.

Planting and dividing


  • Divide and transplant herbaceous perennials to rejuvenate their growth and expand your garden.
  • Plant late-season vegetables, such as kale, spinach, winter radishes, and shallot and onion.
Photo of gloved woman hand holding weed and tool removing it from soil

Weeding and mulching


Keeping weeds at bay and providing insulation for your soil is essential during September. Try these top tips:

  • Regularly weed your garden beds as weeds compete with your plants for space, nutrients, and water.
  • Mulch around established plants to retain moisture, suppress weeds, and protect roots from temperature fluctuations.
  • Consider using organic mulch materials, such as bark chips or compost, for a sustainable approach.

Planning ahead

September is a great time to plan and prepare for the seasons ahead. Here’s a few things you could consider:

  • Start making notes for any changes or additions you’d like. Did something not go as you imagined with your garden this year? Did you learn from something that went wrong?
  • Research spring-flowering bulbs for planting in the coming months.        
  • Take stock of your gardening tools and equipment, ensuring they are clean, sharp, and in good working condition.