Checking insulation and heating Insulation benefits both greenhouses and frames and can be done simply with plastic bubblewrap. If not already done, make time to do it now. Check the heaters. Watering Water the plants only when the soil in the pots shows signs of drying out. Avoid overwatering annuals in pots and any other young plants in the greenhouse, or the roots may be damaged. Take care not to splash the flowers or leave water lodging in the crowns of the plants. Try to water as early in the day as possible, especially in a cold or cool greenhouse, so that surfaces dry before nightfall. Controlling pests and diseases Remove any leaves showing signs of grey mould (botrytis), and discard any cuttings which have diseased stems. Check for pests such as vine weevil and take action if necessary. Where possible use dusts rather than sprays in winter to avoid increasing the humidity in the greenhouse. Sowing seeds If you have a heated propagator available which can maintain a temperature of 16-18°C (61-65°F) during germination, you can start sowing seeds towards the end of the month. Without the extra boost of a heated propagator, delay sowing for another month. Sow greenhouse plants, such as begonias, gloxinias and streptocarpus, and also plants for the garden, including pelargoniums, half-hardy annuals, lilies, perennials and sweet peas. Lilies for forcing If you want to force lilies to produce early flowers pot up the bulbs now. Vines Complete the pruning of vines in the greenhouse while they are completely dormant. Peel or rub loose bark from the stems of mature vines as this can harbour pests over the winter, but do not pull off so much bark that green shows underneath.