At the end of winter it is still uncomfortably cold outside. But even in the unheated greenhouse the temperatures sometimes rise so high that the first radishes and lettuces germinate towards the end of February. This makes growing in the greenhouse a lot of fun.
Growing in the greenhouse: using the right sowing soil
When growing in a greenhouse, you should always use a low-nutrient substrate. In ordinary potting soil, new roots would hardly form, as there are plenty of nutrients available. Only when the young seedlings have to go in search of food will they stretch their fine little roots throughout the entire sowing container and branch out well. Peat-free sowing soil is also available, for example from Floragard.
Spraying instead of watering
Do not water the fine seeds of petunia, basil or busy lily with a watering can and keep them moist. Hand sprayers that produce a fine mist are better. This not only moistens the substrate evenly, but also provides the drought-sensitive seedlings with adequate humidity.
Another plus: seeds or fine seedlings are not washed out of the soil and there is no waterlogging.
Making the most of light
On dull spring days, at least the greenhouse cover must be clear. Only then will a large part of the scarce light reach the sun-hungry seedlings. In addition, the sun heats up the greenhouse much better that way. So get rid of algae, dust and co!
Sowing from February
Early vegetables for the greenhouse, cold frame and open field can be sown as early as February – either at the window or in the greenhouse, where it is much brighter but usually also cooler. Lamb’s lettuce, spinach, broad beans and radishes will not mind much. If, on the other hand, you want to pre-cultivate summer flowers or a fruit vegetable that requires warmth and takes a long time to grow, you can heat the greenhouse with a gas or electric heater. A special paraffin stove is more suitable for smaller houses.
In general, however, the timing of the sowing date should be right. Outdoor cucumbers, for example, should not be planted until after the Ice Saints (mid-May). To prevent the young plants from growing too large, you should wait until mid-April before sowing.
Ensure a good seal
The best heating is of no use if greenhouse walls or door seals do not keep tight. However, many a small leak remains undetected. Here, cold air flows continuously into the greenhouse. A down, held close to the greenhouse shell, detects every crack. It is imperative to seal it before the young plants are planted. Bubble wrap without gaps reduces heat loss through leaks and also increases the insulating effect of the greenhouse cover.
Growing in the greenhouse: germination temperatures, sowing times and germination duration
Andean berry 22-24 °C, Feb./March, 7-14 days
Artichoke 18-25 °C, Feb./March, 15-25 days
Aubergine 22-24 °C, Feb./March, 6-14 days
Cauliflower 15-20 °C, Feb.-May, 5-10 days
Early and forcing kohlrabi 12-20 °C, Feb./March, 5-10 days
Early head cabbage 15-20 °C, Jan-May, 5-10 days
Peppers 22-24 °C, Feb-March, 5-20 days
Radish (direct sowing) 12-20 °C, end of Jan-April, 3-10 days
Lettuce (forcing and early varieties) 8-16 °C, February, 6-12 days
Lettuce (outdoor varieties) 8-16 °C, March-May, 6-12 days
Fleissige Lieschen 18-23 °C, Feb./March, 15-30 days
Bateleur flower 12-20 °C, Feb.-May, 10-18 days
Liverwort (Ageratum) 22-26 °C, Feb./March, 10-15 days
Snapdragon (Antirrhinum) 16-20 °C, Feb./March, 15-25 days
Elf’s mirror (Nemesia) 18-22 °C, Feb.-June, 10-15 days
Lobelia 18-25 °C, Feb./March, 5-15 days
Petunia 18-23 °C, Feb./March, 10-15 days
Midday gold (Gazania) 18-23 °C, Feb-Apr, 10-20 days
Spider flower (Cleome) 18-24 °C, Feb./March, 15-25 days
Verbena 18-24 °C, Feb./March, 15-30