When can you start sowing in a greenhouse?
Written by
Petra
Subject
Greenhouse & Growing
Date
11-01-2025
As soon as the first rays of sunshine get a bit stronger, I always feel that urge to get started again. The garden is calling, the greenhouse is ready, and you just want to begin. But when is the right time to start sowing in a greenhouse?
The good news is that you can usually start much earlier than outdoors. In some cases even as early as January, but for most people March is the perfect time to begin.
Why can you sow earlier in a greenhouse?
A greenhouse creates a more protected environment. It warms up faster during the day and shields your plants from wind and heavy rain.
That means:
-
seeds germinate faster
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young plants grow more steadily
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there is less risk of failed seedlings
Do keep in mind that nights can still be quite cold. This is something many people underestimate.
When should you start sowing?
It depends a bit on what you want to grow, but there are some clear guidelines you can follow. In January and February you can already start, as long as your greenhouse offers some protection against frost. This is mainly suitable for hardy crops like lettuce, spinach and radishes.
For most people, March and April are the best months to begin. The days get longer, there is more light and temperatures start to rise. This is the perfect time to sow crops like tomatoes, peppers, cucumbers and courgettes.
From May onwards, things become much easier. The risk of cold nights decreases and you can sow almost anything without worry. This is also a great time for herbs, flowers and fast growing vegetables.
Greenhouse sowing calendar
| Month | What can you sow in a greenhouse? |
|---|---|
| January | Lettuce, spinach, radish |
| February | Lettuce, spinach, carrots |
| March | Tomato, pepper, cucumber |
| April | Courgette, beans, herbs |
| May | Almost everything |
What should you pay attention to?
In practice, things rarely go wrong because of sowing itself. It is usually the conditions.
A few things that really make a difference:
Temperature
During the day it is often warm enough, but nights can still be cold. You can cover your plants or use a small propagator.
Light
Place your seedlings in the brightest spot possible. Too little light leads to weak, stretched plants.
Water
Do not overwater. The soil should be slightly moist, not soaked.
Ventilation
On sunny days, it can get warm quickly. Opening the greenhouse helps prevent problems.
For most crops, March is the best month. There is more light and temperatures start to rise.
Yes, but only with hardy crops like lettuce and spinach. Extra protection against frost is often needed.
Not necessarily. It can help for early growing, but most people do not use heating.
Radishes, lettuce and spinach grow quickly and are great to start with.
This is often caused by too little light or too much water. Move them to a brighter spot and reduce watering slightly.
