Sun, Soil, and Seedlings: Maximizing Your Cold Frame
Cold frames are a fantastic way to extend the growing season and provide a safe haven for seedlings and delicate plants. However, simply owning one isn't enough. To truly reap the benefits, you need to understand the nuances of cold frame management. This guide covers essential aspects, from optimal placement and temperature regulation to creating a hotbed for an early spring start.
Location: Just like humans, plants flourish in the right conditions. For a cold frame housing growing plants (as opposed to just starting seeds), a south-facing position (in the northern hemisphere) with ample sunlight is crucial. Equally important is protection from harsh northerly or easterly winds, particularly during winter. Imagine it as building a sun trap for your plants. When deciding on the location, observe the prevailing wind direction and, if feasible, position the frame's ventilation opening on the leeward side. This helps regulate temperature without creating drafts.
Hot and Cold Running: Cold frames are susceptible to significant temperature swings. Protecting your plants from frost is vital. Repurposed carpets or sacks make excellent insulators, trapping warmth if placed over the frame before nightfall. Conversely, summer heat can be equally detrimental. Use shade cloth, netting, or shading paint to prevent sunburn and overheating. On very warm days, maximize ventilation by fully opening or even removing the lid. Keep in mind that even with the lid off, shading may still be necessary. A simple solution is to attach strips of hook-and-loop fastener to the frame's corners and matching pieces to a sheet of muslin or an old net curtain. This allows for easy attachment and removal of shading, shielding your plants from scorching and desiccation.
Sturdy Seedlings: Leggy seedlings, reaching desperately for light, are a common problem. To avoid this in your cold frame, elevate pots and trays on bricks, bringing them closer to the top. Ensure the plants don't touch the glass, as this can cause burns or deformities. Rotating the trays and pots every few days encourages uniform growth. A small nightlight placed under an inverted tin can provide gentle warmth during light frosts. Lining the frame's interior with polystyrene sheeting helps retain heat and reflects light back onto the plants.
Building Your Own: Building your own cold frame can be a fulfilling project. Salvage yards often offer old window frames and bricks at reasonable prices. Measure your window frames and construct the frame walls accordingly, ensuring the back wall is taller than the front for optimal light penetration and rainwater runoff. A frame 1.8m (6ft) deep should have a front wall approximately 30cm (12in) high and a back wall around 46cm (18in) high. Railway sleepers, sturdy planks, or concrete blocks can also be used for the walls. Regularly disinfect the frame to eliminate fungal spores.
Hot Beds for Early Starts: Want to give your seeds a head start? Transform your cold frame into a heated propagator with a hotbed. Combine equal parts fresh horse manure and dead leaves, turning the mixture every few days for a couple of weeks. Dig a hole slightly larger than your frame, fill it with the mixture, and position the frame on top. Cover the mixture with soil and add a layer of lime. Allow the bed to heat up for a day or two before use. Never plant directly into the hotbed; instead, sow seeds or plant seedlings in trays or pots, burying them to the rims in the soil. Open the frame when the temperature reaches 21°C (70°F).
A well-managed cold frame can significantly extend your growing season and provide a haven for your plants. Whether you're starting seeds early or protecting tender plants from the elements, a cold frame is an invaluable asset to any gardener. Remember to consider your location carefully, manage the temperature effectively, and utilize the space wisely. A good garden planner will help you keep track of your planting schedule and ensure you make the most of your cold frame. With a little planning and effort, your cold frame will become a powerhouse of productivity in your garden.
