Rain levels have fallen in recent years however, so watering is therefore still high up on the weekly gardening agenda. You will need to gradually reduce watering in step with changes in your local weather, perhaps watering shrubs every 14 days rather than every five days and container plants once a week instead of every couple of days, as temperatures get cooler and rainfall increases.
Stormy and showery weather is common in September, with flood risks and sudden peaks and troughs in water levels. Staking and protection of vulnerable plants will be necessary. Mulching and soil cultivation will help to smooth out the variations in rainfall, reducing pooling and drought in equal measures.
Shorter days, falling light levels, and the lower angle of the sun in the sky will limit growth rates, even on the warmest days.
A well-positioned greenhouse can maximise the available light to good effect, and a vegetable plot with a favourable aspect will improve the possibilities for late cropping.
The quality of the light at this time of year is enough to encourage continuation of late flowering, but may be insufficient for new young green growth to flourish.
Seed sowings and tender softwood cuttings may therefore fail, or else will not come up until next spring. Semi-ripe cuttings (taken from riper wood) are more likely to be successful than softwood cuttings, as they have greater food reserves and are more resistant to rotting, so can better withstand cold conditions.
The first half of the month is usually warmer than the second half. The growing season can often be extended well into September, but only in southern parts of the UK. Applying a mulch in late summer will help to keep the warmth in the soil for longer into the autumn.
Occasional night frosts are common in late September, particularly in exposed areas, on high ground, or in frost pockets.
Have some horticultural fleece handy for the odd night when it is needed before the garden is fully prepared for winter. In exposed and northern areas, winter preparation should already be well underway.
September has a more blustery, autumnal feel than August. Windy weather after a dry summer can lead to early leaf fall, with leaf clearance becoming time consuming by the end of the month.
Staking, pruning and tying-in of climbers should be priorities if windy weather does occur, and will be good preparation for the winter ahead.