The first frosts have already arrived in parts of the UK, which is your sign to get tender plants under cover before they succumb to the ravages of winter.
If you haven’t already done so, check your greenhouse heater’s working, that automatic vent openers are still operating, and clear out cucumbers, peppers, aubergine and chilli plants which have been fully harvested.
As the weather turns cooler, close up the greenhouse in the early afternoon to trap heat, which will help to ripen indoor fruit. Keep dampness to a minimum and ventilate when possible to move air around the plants and keep them healthy.
If you have permanent fruit growing in your greenhouse borders, work in organic matter such as compost or well-rotted manure around them.
Bring in tender plants including cannas and bananas in pots, before the frost damages the leaves, as well as shrubs including azaleas, camellias and daphnes for early spring flowers.
There’s still time to sow Californian poppy, pansies, cornflowers and sweet peas, and plant bulbs for spring colour.
Linda Lane, managing director of family firm Griffin Glasshouses, says key tasks should focus on letting in light, eliminating disease and controlling bugs and pests.
Autumn is a great time to have a good clear-out as you will get rid of pests which might otherwise overwinter in the warmer environment.
“It is essential to keep glasshouses clean and healthy,” she says. “They should not be used to store garden tools, pots, old plant labels and seed boxes as they can harbour pests and diseases. Make sure the glass on both the inside and out is regularly cleaned to maximise the short daylight and sunshine hours we have in the winter.”
Use a proprietary glass cleaner if the panes are particularly dirty, otherwise just plain water, making sure it doesn’t drop on to the leaves of the plants. She advises against using a pressure washer unless it’s a warm day when plants can be taken outside.
“Keep pathways and staging clean and, if necessary, wash over with a non-toxic disinfectant. Repair broken glass because draughts can cause immediate damage in cold weather.”
Where panes overlap, use an old lolly stick or plant label to ease out the dirt, then give the area a gentle slosh with water to remove it completely. Use a scrubbing brush to wash down shelves and staging, making sure you do the underside as well as the top.
It may be too late in the season to repaint or treat wooden greenhouses, but all metal supports should be washed down, inside and out, again ensuring no spillage onto the plants.
You may need to put up insulation to ensure overnight temperatures are kept as high as possible inside the greenhouse, saving money on heating bills.
“Finally, our changing weather patterns suggest we are going to experience a lot more torrential rain, so make sure glasshouse guttering, and other rain harvesting facilities, are working efficiently and are clean.
“On warmer, sunny days, do make sure the glasshouse is ventilated, but remember to close up at night,” warns Lane.