Best tech­niques for tough­en­ing up your plants

Amateur Gardening - - This Week In Amateur Gardening -

IF your green­house and win­dowsills are groan­ing un­der the weight of cut­tings and seedlings, you might be tempted to cre­ate more space by mov­ing some out­side.

But hold fire – ris­ing tem­per­a­tures may seem plant-friendly but nights are cold and the last frosts are still some way off, so mov­ing young plants into the gar­den now could se­verely stunt their growth and kill them. The last frosts usu­ally oc­cur in late spring in the south, and slightly later fur­ther north.

Wait for a few more weeks be­fore start­ing the process of hard­en­ing them off, which is how you pre­pare ten­der and over­win­tered plants for life out­side.

It takes two or three weeks, and dur­ing this time the plant’s leaf struc­ture thick­ens and be­comes wax­ier so it is more able to cope with lower tem­per­a­tures. How­ever, it will not make frost-sen­si­tive plants hardy.

Plants should be hard­ened off in grad­ual stages. Those raised in a heated green­house or in­doors should start by be­ing moved into a cold green­house for a cou­ple of weeks be­fore be­ing placed in a cold frame.

If you don’t have a green­house, go

straight to a cold frame, with the lid open dur­ing the day and closed at night. Keep the lid open for longer dur­ing the next two weeks un­til the plants are left to­tally ex­posed just be­fore plant­ing.

If you don’t have a cold frame, place plants against a shel­tered sunny wall and cover with two lay­ers of fleece. Bring them in at night for the first week, and in the se­cond week take away one layer of fleece. Af­ter this, re­move the fleece al­to­gether dur­ing the day, re­plac­ing it only as dusk falls.

By the end of the third week the plants can re­main un­cov­ered the whole time and should be ready to plant out.

Ac­cli­ma­tise seedlings in a cold frame A cold frame and fleece are two im­por­tant fea­tures of the hard­en­ing-off process

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