Definition - What does Hardening Off mean?
Hardening off refers to the act of moving plants outdoors for specific lengths of time so they become acclimatized to the sunlight, temperature, dry air, and colder nights. The process of hardening off plants is generally done to young seedlings or greenhouse plants that are accustomed to extremely controlled weather and light conditions. η
Hardening off is usually undertaken when the outdoor temperature is above 40 degrees Fahrenheit so a plant does not undergo too drastic of a sudden temperature change before it has a chance to adjust.
MaximumYield explains Hardening Off
Most plants require seven to 10 days to successfully harden off and remain outdoors 24 hours per day. At first, during the process of hardening off, the tender plant is left outside for periods of only two to three hours in a sheltered location. Each day, the plant is left outdoors for longer stretches of time until it is safe to remain outside for a full 24 hours and eventually be planted directly in the garden.
Hardening off plants grown indoors or in a greenhouse helps prevent the plant from undergoing shock from a sudden temperature or light change. A plant that has been hardened-off stands a far greater chance of surviving outdoors than a plant that has been suddenly thrust into a changing environment that it is not used to, including wind, rain, animals, and more.