In The Greenhouse This January

January greenhouse care is all about protection, hygiene, and gentle early starts. A little attention now sets you up for a productive spring.

🌡️ Temperature & insulation 

• Insulate the greenhouse with bubble wrap (horticultural grade) to reduce heat loss.

• Check heaters and thermostats regularly; aim for frost-free (around 5°C) unless growing tender plants.

• Ventilate on mild days to prevent condensation and fungal diseases.

💧 Watering 

• Water sparingly — plants need very little in low light and cold conditions.

• Water early in the day so foliage and soil dry before nightfall.

• Avoid splashing leaves to reduce disease risk.

🌱 Sowing & growing 

• Sow early crops such as lettuce, rocket, spinach, radish and spring onions in trays or modules.

• Start onions, leeks and shallots from seed in gentle warmth.

• Chit seed potatoes in a cool, light, frost-free spot (often the greenhouse itself).

• Start sweet peas in pots for strong early plants.

🧹 Hygiene & maintenance 

• Clean glass and staging to maximise light levels.

• Remove dead leaves and spent plants promptly.

• Disinfect pots, trays and tools to prevent disease carryover.

🐛 Pests & disease 

• Check regularly for aphids, whitefly and red spider mite, especially on overwintering plants.

• Improve airflow to reduce grey mould (botrytis).

• Remove infected plants rather than trying to treat in cold conditions.

🪴 Overwintering plants 

• Protect tender plants (pelargoniums, fuchsias, citrus) with fleece on cold nights.

• Raise pots off the floor to improve drainage and reduce cold damage.

• Check stored bulbs and tubers for rot.

📋 Planning ahead 

• Organise seed packets and plan sowing dates.

• Repair broken panes, vents and door seals.

• Set up propagators or heat mats ready for late winter sowing.