January
Written by Michelle Jenkins
January Greenhouse Growing Guide – Michelle Jenkins
January is the perfect month to prepare your greenhouse for the year ahead. With a bit of care and planning, you can create an organised and productive growing space. Here’s my comprehensive guide to help you grow and maintain your greenhouses this winter.
Preparing A Greenhouse for Spring and Essential Maintenance
Clean and Refresh: Clean your greenhouse inside and out using warm, soapy water. This removes dirt, algae, and pests, while allowing maximum light to reach your plants during the shorter days of winter.
Organise supplies: Check your pots, shelving, trays, labels, and benching. Clean them thoroughly to avoid disease and prepare them for sowing. Take this time to stock up on essentials like seeds and compost.
Review heating and insulation: Aim to maintain a minimum greenhouse temperature of 5–7°C (42–45°F). Frost-sensitive plants may need extra protection on cold nights; horticultural fleece, straw, or even newspaper can provide a buffer against frost. Install a min-max thermometer to monitor temperature fluctuations.
Ventilation: Proper airflow is crucial even in winter. Open vents on dry, sunny days to prevent condensation and fungal diseases. Avoid ventilating during damp or foggy weather, and be sure to close vents mid-afternoon to retain warmth before nightfall.
Inspect equipment: Check heaters, fans, and propagators to ensure they’re in good working order. Replace or repair faulty equipment now to avoid interruptions during the growing season.
Crops and Flowers to Start in January
January is a great time to sow seeds under cover early, giving plants a head start for the spring.
Vegetables to Sow in January
Salad greens: Lettuce and pak choi can be sown year-round for a continuous harvest.
Root vegetables: Early beetroot and carrots germinate well in a greenhouse, producing tender, crisp crops.
Warm-season crops: Use a heated propagator to start peppers, aubergines, and tomatoes, maintaining a temperature of 21–24°C.
Flowers to Sow in January
Flowers bring beauty, support biodiversity, and make excellent companion plants for vegetables by deterring pests and attracting pollinators.
Sweet peas: Sow in long root trainers or toilet roll tubes for their deep roots.
Pelargoniums: Start in a heated propagator at 21–24°C. After germination, lower temperatures to above 8°C. Expect blooms by June.
Antirrhinums (Snapdragons): These need bottom heat to germinate. Once sprouted, keep them in a frost-free greenhouse.
Hollyhocks: Edible and beloved by pollinators, hollyhocks germinate best at 16–21°C.
Additional Tips for a Productive January
Plan your year: Use the quieter month to decide what you want to grow and organise your greenhouse layout for efficiency.
Prepare propagators: Test and clean your equipment so it’s ready for action when sowing starts in earnest.
Think long-term: January is a great time to start perennial flowers or crops that require longer growing periods, giving them a strong foundation for the year ahead.
Thanks for reading our guide on preparing your greenhouse for spring! With the right preparation now, your greenhouse will be set up for a productive growing season ahead. Whether you’re starting early seedlings, improving ventilation, or organising your space, these steps will set you up for success.
Want to stay ahead? Take a look at what’s coming up in February’s growing guide.
