Finally the Ice Saints are over. There is no frost in sight and you can start planting the early plants straight away. Or is it? If your plants have only been indoors so far, you should harden them off first before they are allowed into the beds outside. Here are some tried and tested methods that will help you optimally prepare your young plants for life in the garden.
What is hardening and why is it important?
Hardening off plants essentially means “strengthening” them before they take their eventual outdoor space. This is an important step, especially for sensitive plants, without which, in the worst case, they could even die. For example, they are considered sensitiveYoung plants of tomato, cucumber, peppers etc. that have been grown in the house or greenhouse and have not yet been exposed to external weather influences.
Not just cold and frost, but alsotoo much sunand high temperatures can damage your valuable young plants. It would be wrong to assume that plants grown indoors will do well outdoors when the weather turns mild. It is the sudden changes in conditions that the young plants do not tolerate well.
The gradual hardening off changes the metabolism of the plants. They begin to store secondary plant ingredients that make them more resistant to environmental influences. This process helps the plants grow and thrive better after planting.
When is the right time?
The Ice Saints in mid-May are a tried and tested time from which frost is supposedly no longer to be expected. But it is also advisable to monitor local weather conditions and especially soil temperatures. The weather is not the same every year. Ideally, the soil should have a constant temperature of at least 15 degrees Celsius before the sensitive plants can be moved outside permanently.
The period after the Ice Saints is usually a good time to begin the hardening phase of the young plants so that they are ready to be planted out in a few weeks.
Harden off young plants: gradually accustom them to sun and wind
All young plants grown indoors are used to the uniform conditions indoors and are sensitive to direct sunlight and wind. Therefore, you should strengthen them before exposing them to the adverse outdoor conditions.
Young plants and the sun: getting to know each other for the first time
Start by placing the plants in a shady location outdoors. This should initially only be done for a few hours a day and can gradually be extended to full days. After a few days in the shade, the plants can then be exposed to direct sunlight for hours at a time, increasing the duration of sun exposure each day. This method helps avoid sunburn and stress.
This way you can accustom the plants to wind
Wind plays an important role in strengthening plant stems. Young plants grown in a sheltered environment are often not accustomed to wind, making them vulnerable to damage if permanently moved outdoors.
Start with light air movements and gradually increase the intensity to allow the plants to adapt to the conditions. To do this, you can first turn on fans around the pots with the young plants to imitate wind movements. This will strengthen the stems. When hardening off in the garden, you can first place the plants in a high-sided box so that they are only gently blown by the wind for the first few days.
Adaptation to temperature fluctuations
Night temperatures can drop significantly, especially in spring. To get the plants used to this, they should initially only be taken outside during the day and back inside at night. Monitor the weather forecast carefully to protect your plants from unexpected frost.
Complete the hardening process
After one to two weeks of gradual hardening off, depending on the specific needs of your plant species and weather conditions, your young plants should be ready to be permanently transplanted outdoors. Make sure they are well watered and have enough support for their continued growth,such as climbing aids.
Hardening in a week: this is how it works
If the weather is right, you can harden off your young plants in just one week. Here are step-by-step instructions.
Day 1: First introduction to the outdoors
Place the young plants on a tray that you place in the shade outdoors for a few hours. This gives the plants the opportunity to slowly acclimate to outdoor conditions without being exposed to direct sunlight. Then bring the seedlings back into the greenhouse or house.
Day 2: Indirect sun
Place the young plants in an outdoor location where they receive indirect sunlight, for example in partial shade under trees, for a few hours. Then bring them back in a protected place.
Day 3: Direct sunlight
On the third day, the young plants are allowed to be in direct sun for three to four hours. Make sure they are well watered before going outside. After sunbathing, the plants go back home.
Day 4: Extra hours of sunshine
Increase the time in direct sun to five to six hours. This further strengthens the seedlings and prepares them for the next full day outdoors.
Day 5: A full day outdoors
Leave the seedlings outside all day, from morning to sunset. Bring the plants back into the house or greenhouse after sunset. The last night inside is approaching.
Day 6: First night in the garden
Leave the young plants outside all day and night. Check them in the evening and make sure they are protected from pests. You can place them elevated, for example on a garden table.
Day 7: Planting outdoors
Plant the seedlings outdoors in the late afternoon. This time allows the plants to recover from the move without the strong midday sun. Avoid planting in the morning or during the strongest sunlight to avoid additional stress.
By carefully hardening off your young plants, a successful transition into the garden is guaranteed! It requires patience and attention, but the reward is a healthy, vigorously growing garden that's worth the effort.
Cover photo: Shutterstock / Paul Burr
