Pests & Dideases

Vegetables

Sow vegetables for over wintering, to mature next spring: turnip, spinach, winter lettuce, Oriental vegetables and seed of over wintering onions, both salad and bulb types. 

Plant outdoors

Spring Cabbages can be transplanted, spacing them 30cm (12”) apart. Overwintering onion sets in late September

Calabrese.

Harvesting

Dig up potatoes before slug damage becomes a problem.
Regularly pick fast maturing vegetables, such as French beans, runner beans, courgettes, cucumbers, peppers and tomatoes, to prevent them becoming stringy, tough or bitter and to encourage further crops.
Remaining outdoor tomatoes should be picked by the end of the month and ripened indoors. The whole truss can be cut off to allow the fruits to ripen ‘on the vine’, perhaps under a cloche or on a windowsill.

Lift onions and shallots once the foliage has started to die back.

If very cold, carrots, beetroot and turnip are best lifted and stored for use over the winter. Only store intact roots. Parsnips should be left in, as they taste better once frosted.

Harvest sweetcorn as it becomes ripe.

Marrows, pumpkins and squashes may be ready for harvesting.

Fruit

Lift and pot up rooted strawberry runners from vigorous plants.
Water any new strawberry beds planted this season. If you have not yet planted new beds, this is really the last chance to do so. New plants need to establish before the cold sets in.
Cut out fruited canes of summer raspberries and tie in new canes that will fruit next year. Select strong, healthy canes and cut out weak, forked or misplaced ones (such as those growing out into the paths).
Blackcurrants are often pruned commercially this month (straight after harvesting), but it is better for home gardeners to wait until the leaves have fallen, and to prune the plants while dormant during the winter. Valuable time is best saved for more urgent jobs that cannot wait beyond this month.
Pick apples and blackberries.
Pick autumn raspberries as they start to ripen.

New trees can be planted once the autumn sets in and the dry weather is over. 

Remove apples, pears and plums affected with brown rot to prevent the disease from spreading.
Towards the end of September, start fixing grease bands around the trunks of fruit trees.
Net or cage ripening fruits to protect them from birds.
Monitor yields on soft fruit crops, as older plants frequently become infected with viruses, which reduce yield. They may need replacing.
Prune out any dead, dying or diseased shoots on fruit trees that are affected by diseases such as bacterial canker, cherry leaf scorch, powdery mildew or other problems that can overwinter or continue to worsen. Avoid pruning stone fruits (e.g. cherries or plums) once they are dropping their leaves. 

Herbs

Take cuttings of rosemary, lavender.
Cut back flowered herbs, such as marjoram, to encourage a second flush.
Divide herbs before they die back in the cold, in order to keep clumps potted up in the kitchen for winter use.

Around the Garden

Keep up with watering winter squash and pumpkins: this will prevent their growth from being checked. Use stored rainwater wherever possible.

Celery can be earthed-up for the final time this month. Self-blanching types are less hardy, and should be harvested before the first frosts. Trench cultivars can be left in the ground, although do have horticultural fleece or straw handy to throw over the tops if severe frosts are forecast.

Sow green manures, such as mustard and Italian ryegrass.


Keep up with potato blight and tomato blight control. Outdoor tomatoes are more vulnerable. Blighted potato haulms can be cut off and burnt. The tubers can still be harvested. Potato powdery scab is prevalent in wet weather at this time of year, especially on clay soils. Dispose of affected tubers and rotate crops to prevent the problem building up in the soil. Common scab and other potato skin problems can be prevalent in dry Indian summer weather, particularly on well-drained sandy soils. Watering is key, and the use of acidic fertilisers may help if you have alkaline soil (which worsens the problem).

Be sure to clear debris created when lifting potatoes, and take care not to damage the haulms. Potato debris left out in wet weather could cause the development of fungal diseases such as black leg or fluffy grey mould.