Watering and feeding As the days get shorter and the nights become colder, progressively reduce damping down and watering in the greenhouse. If it is still necessary, try to do it before midday. Stop feeding plants. Heating Check the greenhouse heating and make sure it is working properly and that thermostats are operating correctly. To save heat during the winter, line the greenhouse with plastic sheeting or bubble plastic. There are special clips you can buy to hold them in place. If you are using an oil or gas heater leave the ventilators on the sheltered side of the roof open 5 mm (1/4 in) the whole time to allow fumes and moisture vapour, created by the heater, to escape. Clean the glass before fastening plastic lining or bubble plastic inside the greenhouse - dirty glass excludes valuable light. Cover the ventilators separately. If using single plastic sheeting ensure that a gap of about 2 cm (3/4 in) is left between the glass and the insolation to maximise the double glazing effect. Cold frames Make sure that the frames are closed each night to protect any overwintering plants in case of a sudden, unexpected frost. Cover with matting as an added precaution. Take any tender plants out of the frames and into the greenhouse without delay. Controlling pests Keep a sharp lookout for damage caused by slugs or other pests. Sowing Sow sweet peas without heat and continue to sow hardy annuals. Sow lettuces to overwinter. Cuttings Continue to take cuttings of tender perennials and to pot up cuttings that have rooted. Bulbs, corms and tubers Prepare bulbs, corms and tubers for storage and pot up lilies for early flowering. Vines Continue to pick bunches as they ripen. Treat the vines if red spider mite and mildew have been a problem.