harden off

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harden something off

to accustom a young plant to normal weather so it can be moved from a protected environment to the out-of-doors. We put the plants by the open window to harden them off. We hardened off the plants.
See also: harden, off
References in periodicals archive ?
Harden off autumn-sown cauliflowers being overwintered in frames, so they will be ready for planting out in March.
Transplant seedlings once the first leaves have formed and harden off before planting out at the end of spring, placing the seedlings around 30cm (12in) apart in rows 45cm (18in) apart.
If you are sowing indoors, harden off seedlings before planting in a greenhouse border or polytunnel in late spring, or outside in a sunny, sheltered spot from midsummer.
Harden off autumn-sown cauliflowers being over wintered in frames, so they will be ready for planting out in March.
Take cuttings from summer-flowering clematis n Plant dormant dahlia tubers and young plants n Harden off hanging baskets and windowboxes ready to put in position outdoors when all danger of frost has passed n Begin feeding plants in containers and continue throughout the summer Renovate lawns by applying moss killer and then rake out the dead moss and accumulated debris n Pinch out the tips of all side shoots growing from main rod framework of outdoor grapevines n Thin gooseberry fruits, using the crop for cooking
When the first two leaves are welldeveloped, gradually harden off before planting out - but don't do it too soon as they are frost-tender.
Start standing bedding plants outside on warm, fine days to help them harden off.
Begin to harden off young plants and over wintered cuttings.
When three leaves have emerged, plant seedlings in soil that has been warmed under a cloche and then harden off under a cloche.