Definition of harden something off in US English:

harden something off

phrasal verb

  • Inure a plant to cold by gradually increasing its exposure to it.

    • ‘Place them out of direct sun on a light windowsill or in the greenhouse to grow on until they can be hardened off and planted out at the end of May.’
    • ‘Eggplants are very sensitive to transplant shock, so take extra care to harden them off properly.’
    • ‘Not everyone has the luxury of a greenhouse, but plants can be hardened off by taking them outdoors during the day and bringing them in again in the late evening.’
    • ‘Gradually harden them off over three to five days by putting them in a protected shady spot, first for half a day, then a full day, and then gradually into full sun.’
    • ‘Don't put them outdoors, though, until all danger of frost has passed, and remember to harden them off properly.’
    • ‘A week or so before transplanting outdoors, harden them off, stop fertilizing and watering, and put plants outside each day to help them adjust to new growing conditions.’
    • ‘We've hardened the turf off with some high-potassium fertilizers and tried to keep any water on the surface of the greens to a minimum.’
    • ‘First the seedlings are hardened off by moving them outside in the flats for an hour or two the first day and increasing the time until, in a week, they stay out around the clock.’
    • ‘Add moisture retaining granules and slow release fertiliser to the compost and gradually harden the plants off before putting them outside completely at the end of the month.’
    • ‘I hardened it off for growing outside and transferred the whole lot into a large, blue glazed pot.’