With a cold frame you can celebrate the opening of the season in the garden when sowing outdoors is not yet an option. When exactly the starting signal is given depends on the filling. This guide gives tips on how you can influence the date for planting.
When can you plant a cold frame?
Planting a cold frame can begin as early as February, depending on the filling. With a filling of stable manure, which generates heat, lettuce, radishes, kohlrabi, cress and early carrots can be sown. With compost and garden soil, the starting signal is closer to mid-March.
Planting time starts in February – under one condition
So that a cold frame keeps what the name promises, it is placed in a sunny location with a southern orientation. In early spring, solar power alone is not enough to achieve growth-promoting temperatures in the cold frame. Only when filled correctly can you generate heat that encourages seeds to germinate and young plants to grow. This is how it works:
- Mark the contours of the cold frame box at the intended location
- Dig a 50 cm deep pit at this point
- Fill in fresh horse or cow manure up to 20 cm
- Pour a mixture of half-ripened compost and garden soil on top
- Set up and close the cold frame
The decomposition process in the manure produces the desired heat within 8 to 10 days. This way you can sow and plant in the cold frame as early as February. If you limit the filling to compost and garden soil, the window for the planting season only opens in mid-March due to the lower heat development.
Not all plants are suitable for growing in cold frames – tips for choosing
All efforts to find a sunny location and natural heating will be in vain if the planting plan is not correct. Only ornamental and useful plants that thrive at low temperatures are suitable for cultivation in cold frames. The following overview lists the most popular candidates:
- February: lettuce, radishes, kohlrabi, cress and early carrots
- March/April: Preparing cucumbers, tomatoes and peppers for later planting
- September/October: endive, lamb's lettuce, lamb's lettuce, leek
You can sow late varieties of radishes and winter spinach in the cold frame until mid-October. It's not too late in autumn for fast-growing lettuces such as 'Yellow Round'.
Tip
Before filling your cold frame, line the base with sturdy wire mesh. Voles are magically attracted to the seductive scent of the filling and plants. Without appropriate protective measures, seedlings and young plants are destroyed in no time.
