Martin Fish says take care with winter watering
Making sure greenhouse plants have enough moisture is a real art!
Watering in the greenhouse is important at any time of the year, but it’s vital to get it right during the winter months. Too little water and plants being over-wintered will dehydrate. If they get too much, they’re prone to rotting off at the roots. Gauging the correct amount to give plants in the colder months can be difficult and less is best as a rule, but at the same time you still need to give enough to keep them ticking over.
In my greenhouse, where I maintain frost-free conditions, I check the plants a few times a week, and one of the best ways to test if a plant needs water is to pick up the pot. If it feels light, it means the compost is drying out, whereas if it’s heavy, the compost will be wet. When I do water, it tends to be in the morning and, if possible, on a day when it’s bright. This helps to dry out any water splashes and keep a dry, airy atmosphere, which is ideal for overwintering most plants. It also helps prevent fungal diseases and moulds developing on plants. In the winter I never water from overhead; instead water is carefully directed onto the surface of the compost, and I try not to splash the foliage too much. If a plant has really dried out, I find the best way to moisten the compost is to stand the plant in a shallow saucer of water for a while to give the compost time to draw up moisture. For most plants I use water from rain-saving butts, but this can be cold and shock plants in winter, so I always fill the cans after watering and stand them in the greenhouse where the water can warm up slightly. With careful watering and frost-free conditions, you can successfully overwinter many tender plants.