Hardening-Off

HARDENING-OFF – The practice of “toughening” young plants started indoors or under glass, so as to accustom them to outdoor, open-air conditions, especially when these involve lower temperatures. It consists mainly of reducing the amount of water supplied and gradually increasing the ventilation until the plants (while still in hotbeds or coldframes) are open to the sky and entirely unprotected – except when the weather is unfavorable. This may be done with seedlings in flats or beds, with pot plants or with rooted cuttings, grafted plants, etc.