Pronunciation/ˈhɑːd.nɪŋ ɒf/
General Description
Hardening off is the process of gradually acclimatising young plants, seedlings, or tender plants to outdoor conditions after being grown in a protected environment such as a greenhouse, indoors, or under grow lights. This step ensures plants can withstand fluctuations in temperature, wind, and sunlight.
Detailed Description
When plants are raised in controlled environments, they are shielded from harsh weather, intense sunlight, and wind. Hardening off allows them to build resilience before being permanently transplanted outdoors. This is done by gradually exposing them to outdoor conditions over a period of 7–14 days.
The process involves:
- Placing plants outside for a few hours a day in a sheltered, shaded spot, gradually increasing their time outdoors
- Gradually exposing them to more direct sunlight, cooler night temperatures, and wind
- Reducing watering slightly to mimic natural conditions without letting the soil dry out completely
Hardening off prevents transplant shock, which can stunt growth or even kill young plants. Tools such as cold frames or cloches can be used to provide partial protection during this period.
Scaling
For home gardeners, hardening off is typically done on a patio, balcony, or in a sheltered part of the garden. Plants are moved outdoors and back indoors daily until they are fully acclimatised.
In commercial horticulture, large batches of seedlings are hardened off in outdoor nurseries or shaded frames. This may involve using automated systems to control shading or watering, ensuring consistent results across a larger scale.
Etymology
The term “hardening off” comes from the idea of making plants “hardened” or toughened to endure the challenges of outdoor conditions. The phrase has been in use in horticultural contexts since the 19th century.
Funny Flora
Why did the seedling bring a jacket outside?
Because it was hardening off for the weather!