Even on gloomy and overcast days in the summer, the greenhouse temperature can shoot up. By autumn though, it reverses and can plummet to dangerous levels for plants in a matter of minutes.
With our rapidly changing weather patterns, driven by climate change, greenhouse owners need to start planning now to make them fit for autumn and winter, warns greenhouse expert Linda Lane, managing director of Griffin Glasshouses (griffinglasshouses.com).
“It’s all about hygiene and common sense,” says Lane. “The greenhouse will give plants a lot of protection but, with all that glass, temperatures change rapidly, so take precautions. It is also an attractive location for pests to overwinter, so regularly check for attack and treat with proprietary controls.”
As autumn approaches, she shares some top tips on what to do now and during the cooler months, to keep your greenhouse and plants in top condition.
Jobs which won't wait
1. Repair all broken glass, damaged door and window fittings, leaks and bad framework.
2. Remove all plant pots and seed trays and store elsewhere. They are havens for overwintering slugs, snails and other pests.
3. Check heating systems and repair as necessary. Do you have sufficient fuel? If you are not heating the greenhouse, buy rolls of horticultural fleece to protect plants in frosts.
4. Check that interior lighting works properly.
Jobs to do before the first frosts
1. Clear out all plants and thoroughly disinfect all glass frames, staging tops and floors.
2. Clean the glass inside and out, as plants need to maximise the diminishing autumn and winter sun.
3. Protect all taps from freezing, including those inside greenhouses.
4. In cold areas or if overwintering particularly tender plants, double glaze greenhouses with bubble wrap. This can be attached to all Griffin Classic glazing systems with Alliplugs, which are widely available online.
5. Keep the inside clean and on warm or sunny days open doors and windows in the daytime.
Lane is currently busy working in her garden in preparation for the seasons ahead.
“Now is the ideal time to take cuttings such as geranium, penstemons, lavender, species of fuchsia and even more exotic shrubs such as ceanothus. They need to be kept moist and warm and, as temperatures fall, take them into the greenhouse overnight,” she says.
“But don’t leave them where potentially hot early morning sun can cause damage. It will still be safe to take them outside in the daytime until the first warning of frost and then overwinter them in the safety of the greenhouse.”
With spring in mind, now is also the time to sow some annual seeds such as cornflower and nemesias. They will grow on in a cool greenhouse and be ready to plant out to give an early burst of spring colour to the garden.
“Don’t forget to move those tender plants back into the protection of the greenhouse before the frosts start, but do check pots and containers for unwanted pests such as slugs and snails,” Lane advises.
“They would love to overwinter in your greenhouse, feasting on your plants, cuttings and seedlings. So remove them, and throughout autumn and winter, check all plants regularly for pests, diseases and mildew and take remedial action.”