Hardening off young plants correctly
Pre-raised young plants are used to the protected climate on the windowsill or in the greenhouse: even warmth, no wind, filtered light. If they go outdoors without transition, sunburn, wind damage and a growth halt threaten. Hardening off gradually accustoms them to the harsher outdoor conditions.
The effort is small, the effect great: well-hardened plants establish much better and are more resilient.
In short
- Hardening off = gradually accustoming to sun, wind and cold.
- Duration: about 1–2 weeks before planting out.
- At first only a few hours in a sheltered, part-shady spot.
- Avoid full midday sun and night frost at the start.
Why harden off?
Indoor-raised plants have soft tissue and no protective waxy layer against intense UV radiation. Without acclimatisation they react with pale sunburn spots, wilting leaves and stress. Hardening off prompts them to build firmer tissue and protective mechanisms.
How to go about it
- Days 1–3: place the plants for 1–2 hours in a wind-sheltered, part-shady spot, then bring them back in.
- Days 4–7: extend the time outdoors daily and get the plants used to more sun.
- From day 8: leave the plants out at night too, provided no frost is expected.
- Watering: water a little more sparingly – this makes the plants tougher.
Planting out afterwards
After one to two weeks the plants are ready for the bed. Plant preferably on a cloudy day or in the evening so the young plants establish gently. Warmth-loving crops go outdoors only after the Ice Saints.
Frequently asked questions
What happens if I don't harden off?
The plants often get sunburn, wilt and take a long time to recover – in the worst case they die.
How do I recognise sunburn?
By pale, silvery-white to brownish, dry spots on the leaves. Then give more shade immediately.
Tip
A part-shady spot under a tree or by the house wall is ideal for the first hardening days – there the plants get light but no full midday sun.
Caution
Never place freshly put-out plants straight into full midday sun – the UV shock causes sunburn within hours.
Our young plants are strongly pre-cultivated – with a few days of hardening off they start perfectly into the bed.