It’s all too easy when the weather turns cold to forget about checking on the plants that are tucked up in the greenhouse. But just because these plants are dormant it doesn’t mean they don’t need a bit of attention now and again.

Damp air

One of the biggest problems plants face at this time of year is damp air which can cause moulds to develop and rot to set in. The still, cool, moist air in a winter greenhouse provides the perfect conditions for mould to form – if you spot grey, fluffy growth on plants then that’s mould. Ventilation in a greenhouse is key to keeping on top of this problem, so on mild days open the vents for an hour or so to allow for some air flow. It’s best to do this between mid-morning and early afternoon so that the temperature inside the greenhouse doesn’t drop too much, but make sure you don’t forget to close them again! If you have a power supply in your greenhouse you can use an electric fan to circulate the air on days when it’s too cold to open the vents.

Watering in winter

Keep watering to a minimum, and take care when watering not to splash the plants. Mulching the top of pots with grit can help to drain moisture away from the crown of a plant and prevent fungal spores being transferred to the foliage from water splashes.

Plant care

Good plant hygiene is really important too. Every week or so take a bit of time to check over each plant, removing any yellowing or dead leaves, any fading flowers and any growth that shows signs of mould. Wash your hands and if you’ve used secateurs give them a clean with an antibacterial wipe before you touch another plant to avoid spreading diseases and mould spores.

Clean glass

Keeping the glass clean, both inside and out, will also maximise the amount of light that enters the greenhouse at a time of year when it’s hard to come by.

Keep an eye on the weather forecast

If you don’t heat your greenhouse keep an eye on the weather forecast. Severe cold weather will mean the temperature inside the greenhouse will plummet, putting plants at risk from frost damage. Temporarily covering plants overnight with bubble wrap, old blankets or hessian sheets will provide extra layers of insulation, but remember to remove these during the day so that the plants get some light and air flow.

Start sowing

If you’re keen to start sowing there are a couple of crops you can sow/plant in the greenhouse this month. Broad beans are one of the hardiest crops and if you sow them now – a little heat from a heated propagator will speed up germination – you’ll have good-sized plants come spring. Garlic needs a spell of cold weather to produce healthy bulbs in summer, so over the coming weeks pot up individual cloves into modules or 9cm pots. You can also sow onion seeds, and for some summer blooms start off sweet peas now.