Mini greenhouses

What a mini greenhouse can do

A compact greenhouse creates a warmer, calmer pocket of air for seed sowing, hardening off young plants and extending harvests. It is ideal for salad leaves, herbs, chillies, tomatoes and tender seedlings. Think of it as a season-stretcher rather than a frost-proof room: temperatures can still fall sharply overnight and climb surprisingly fast in spring sunshine.

Choose the right format for your space

Cold frames are low, stable and excellent for hardening off. Tall shelf models give more growing area for a small footprint, while lean-to cabinets benefit from the warmth and shelter of a wall. Lightweight zip-cover models are affordable and easy to move but need firm anchoring. Timber looks natural and insulates well; aluminium is slim and durable; polycarbonate is lighter and safer around children than glass.

• Measure with doors and lids fully open
• Choose the sunniest practical position with easy access to water
• Check that shelves can be removed for taller crops
• Prioritise adjustable vents and secure catches

Ventilation matters more than maximum heat

On bright days, open vents or doors early to prevent scorching and fungal disease. Water in the morning so foliage can dry before night, and stand pots in trays rather than leaving compost waterlogged. A minimum–maximum thermometer quickly shows how conditions change. In cold spells, horticultural fleece inside adds useful protection, but remove it when temperatures recover.

Make every centimetre productive

Use lower shelves for seedlings that tolerate shade and reserve the brightest level for sun-loving crops. Sow small batches every few weeks rather than filling the space at once. Keep labels clear, remove dead leaves promptly and clean glazing at the start of spring. In autumn, the same structure can shelter herbs, overwinter tender pots and keep winter salads growing.