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How to use a cold frame

Probably a bit of a horrendously stupid question, but I've never had one before.

 

Given that the last frost in Dundee is very late April.Early May, how early can i start to stick fairly large seedlings out in the frame? Its a plastic sheet type job on a south facing wall that gets plenty of sun.

Posts

  • fidgetbonesfidgetbones Derbyshire but with a Nottinghamshire postcode. Posts: 16,456

    Depends on the seedlings. If frost tender annuals, then during April I would put them in the cold frame. Take the covers off during the day, or open lid to its widest. At night close them up. If a frost is forecast lay a sheet of newspaper or fleece over the plants to give added protection. Hardier perennial plants could go out earlier, give as much ventilation during day as possible, close up at night.

  • Grand, thanks. I'll give the herbs another few weeks worth of sprouting and leave the sunflowers on the windowsill 'till mid April.

  • PalaisglidePalaisglide Posts: 3,414

    Jimmy, there are no stupid questions just requests for information and others may well be waiting for the answer too.

    A cold frame being close to the soil will often be six or more degrees warmer than something on the ground not sheltered from winds and rain. Yours is South facing and will be warmer even on dull days. If you put the pots into a tray in the cold frame, cover at night against the odd frost even we get in the NE of England then all will be well. I use fleece though newspaper or bubble wrap draped over the pots held up from the plants with short sticks will be fine open during the day to allow the plants to breathe and acclimatise 

    Frank.

  • LucyLLucyL InvernessPosts: 163

    Well i'm glad i have found this thread! as i bought a small glass cold frame sthe other week and will soon be usuing it for the first time, so this information has been very helpful!

    My Coldframe is on gravel will that make a difference to how warm/cold it will get? Mine is sheltered by the house and a bush, but will get sun most of the day. Also I am in Inverness Scotland image

  • Tropical SamTropical Sam Posts: 1,488

    A slab in full sun will be warmer than gravel. Black slabs will store heat and white ones reflect it Lucy.

  • LucyLLucyL InvernessPosts: 163

    Great thanks image

  • PalaisglidePalaisglide Posts: 3,414

    The idea of a cold frame is to safe guard young plants against the vagaries of the weather. My own are against a brick wall that takes in heat from any sun we may get and gives it back at night as does the lean to greenhouse. The sides  taller at the back than front to allow the top lights to open yet let the rain run off without damage to the plants. The top light can be left open all day the harden off plants and closed at night against a drop in temperature. The tall sides provide shelter from winds and some shade from direct sunlight. Used properly they can be a production line from seed tray to greenhouse to cold frame then into the ground, hardening off being essential for most young plants before placing them at the mercy of our weather in the open. Inverness much like the NE of England next to the North Sea can have dramatic weather changes, this week in one day hot sun driving rain hail then back to sun and that was only the morning. Cold frames are a big help.

    Frank

  • Stephanie newish gardenerStephanie newish gardener Aberdeenshire/Moray coastPosts: 453

    I've got some tomatoes, french beans and various flower seedlings that have all been grown indoors, mostly starting in a propagator in the airing cupboard and mostly now decorating the very sunny dining room.

    We have both a cold frame and a greenhouse and I've never used either before so have a couple of questions, particularly in response to Frank's production line order of seed tray to greenhouse to cold frame.

    If I put the seedlings from the dining room windowsill into the greenhouse I assume they won't necessarily harden off there because the greenhouse gets lots warmer than the dining room.  Obviously at night it is quite a bit cooler than being indoors.

    Equally, the cold frame gets quite a bit of sun but I assume it won't get quite as hot as the greenhouse but will still be cold at night

    So my concern is how do I acclimatise the plants by using an environment that potentially encounters greater extremes of temperatures?  Or am I being too cautious and should I just stick the toms in the GH and the rest in the coldframe before planting in the garden in a week or so?

    The toms will most likely stay in the GH as I've never had much success with them outdoors up here in Aberdeenshire, so presumably I could start to put them out there soon?

    I put the beans out for the day yesterday as it was mild and sunny but had to shelter them from the wind, and today has been less reliable so they stayed indoors, which is hardly getting them used to being outside!  I think I'll end up putting some in the frame and putting some outside gradually, assuming the daytime temp now stays above 10C

     

  • fidgetbonesfidgetbones Derbyshire but with a Nottinghamshire postcode. Posts: 16,456

    They have to do the hokey cokey. Out in the day in a sheltered place so they don't get too hot. At night they go in so they don't get too cold. A week of that and they should be ok to plant out, but have fleece or newspapers on hand to cover up at night if it gets cold.

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