Skip to content

Allotment & Vegetable Gardening in September

Colourfull Autumn harvest

September is the end of summer although we're often lucky to have a bit more summer and sunshine, nothing is certain with the weather. The bulk of the harvest comes home now and as crops come out the plot begins to empty


The main crop potatoes should be ready now. To repeat August’s advice regarding harvesting potatoes:

When you harvest your potatoes take care to remove all the tubers. Any left will not only sprout next year and becomes a weed but will also be a reservoir for disease and potato blight spores. It’s often worth forking over a few days after harvesting potatoes because more seem to miraculously appear.

If blight has struck your potatoes the best method to preserve the crop is to remove the haulm and dispose of it then leave the potatoes in the ground for a fortnight or longer to stop the spores getting onto the tubers.

It’s best to harvest potatoes fairly early in the day, rinse them off as they come from the ground and then leave in the sunlight for a day to thoroughly dry off and harden the skins before storing.

Sort carefully and place perfect specimens into hessian or paper sacks in a cool dark but frost free place. Damaged tubers should be used first before they have a chance to rot and spread their rot to the rest of the sack.

It’s worthwhile to empty the sacks after a few weeks or a month and check that there are no potatoes going off. Discard these before they rot the sack. You might like to pop a few slug pellets into the sacks as well. It’s amazing how the slugs can appear no matter how careful you are. If you are concerned about slug pellets, remember these are in store and present no risk to wildlife.

Runner Beans

You may well have reasonably sized parsnips now but they will stay perfectly happy in the ground and do taste better after they have had a frost on them.

The runner beans and French beans will be continuing to produce and the last of the peas should be coming in. Compost the foliage of the peas but leave the roots in the ground as the nodules on them contain nitrogen.

The harvest will be in full swing and in addition to the above you should have:

  • Beetroot
  • Cabbage
  • Carrots
  • Cauliflowers
  • Courgettes
  • Cucumbers
  • Globe Artichokes
  • Kale
  • Kohlrabi
  • Lettuce
  • Leeks
  • Marrows
  • Onions
  • Pumpkins
  • Radishes
  • Spring Onions
  • Spinach
  • Sweetcorn
  • Tomatoes
  • Turnips

 From the greenhouse you should be picking aubergines, chilli and sweet peppers as well as cucumbers and tomatoes. If you grow fruit then the picking should be in full swing there as well:

Apples, pears, plums, peaches from the trees, blackberries and raspberries from the canes and strawberries from the bed.  

Sowing, Planting and Cultivating


There’s not a great deal to sow now but surprisingly it’s the right time to sow winter lettuces such as Arctic King for spring harvests.

The other salad crop is the winter hardy spring onion. I’d suggest White Lisbon but ensure it is the winter hardy version.

Green Manure

Early September is the time to sow green manures. If you do not need to dig over your plot as you do with heavy soils or intend to spread manure on a patch then following on the last of a crop with a green manure is a great idea.

The first benefit is that the green manure will hold onto soil fertility that would otherwise be washed out by the winter rains. In fact, sowing a legume such as Winter Tares will fix nitrogen from the air.

Secondly, they will prevent weed growth so you will have less work to do.

Finally, they help improve the soil structure. In the spring you just need to dig over and allow them to rot down for a few weeks.

One of the best green manures for winter growth is Hungarian grazing rye. It continues to grow, albeit slowly, in cold weather and should be around 15″ tall come the spring from an early September sowing. Not only will you have a lush mass of foliage, but it also produces a mass of roots that will provide humus for bacterial breakdown.

Planting out

Your spring cabbage plants can be planted out now and over wintering onion sets can go in for an early onion harvest.

You can plant out garlic as well although I prefer to plant it out later in the year.



Tidy up the summer fruiting raspberries, cutting off the canes that have fruited and tying in the new shoots that will bear next year.
The summer fruiting strawberries can be attended to now as well. Cut off the foliage about 1″ from the ground, clearing and weeding as you go. Any runners can be planted up to replace 3 year old plants that are best replaced now.

General Tasks

Keep an eye on your brassicas for butterfly eggs and caterpillars, these will most probably be under the leaves. The greenhouse pests should be declining but keep an eye out if the weather is good.

Making Compost

If you’ve not already done so, empty your compost bins. The compost that is ready can be spread on the ground and the compost only partially rotted returned to the bin to finish off.

You will probably have quite a bit of foliage ready to compost and building a heap properly will help the transformation from green waste to valuable compost. At the base of the heap place woody material, sweetcorn stalks etc to allow some airflow up into the heap. Next place a 15cm layer of green material and add some sulphate of ammonia or dried blood to add nitrogen. Just a small sprinkling is sufficient, about 50g per square metre (2oz per square yard) is about right.

Another layer of green material but this time lightly sprinkle with lime to keep the pH up. Repeat the process and top off with a piece of old carpet or some plastic sheeting to stop it getting too wet in the rain and to keep the heat in.

The heap should heat up after a few days and be ready to turn in four or six weeks. The smaller the particles the more surface area they have relative to weight and the faster they will decompose. If you have a shredder, this will be ideal but otherwise cut things up with shears, crush things like brassica stems and they will go down much faster.

If you don’t have a shredder but do have a hover mower you can lay foliage on the lawn and run over it with the mower to shred it.