Cold frames are the unsung heroes of allotments, veg plots and gardens. Whilst the upmarket and expensive greenhouse grabs the headlines (along with that comfy old chair, stack of gardening magazines and full tea-brewing paraphernalia) the hardworking, unassuming cold frame pays back its owner hundreds of times over and asks for little in return. Where a greenhouse could be compared to a pampered pedigree pooch demanding attention at every turn, a cold frame is an undemanding, loyal, no nonsense friend. Every garden should have one.
First and foremost a frame allow gardeners to over winter those slightly temperamental seedlings and, thinking ahead, allows seedlings to become acclimatized to nippy spring temperatures. In other words, the addition of a frame instantly extends the growing season at both ends of the calendar. You know what it’s like in April – windowsills are groaning under the weight of seed trays and pots, the weather forecast is saying frosty nights and your seedlings are getting more leggy and drawn by the day. A cold frame is ideal for getting those seedlings used to outdoor life without actually plunging them into cold, wet soil with air temperatures getting down to zero degrees C. Think of a cold frame as the reception class for your seedlings before big school starts for real!
And at this time of year your gooseberry and soft fruit cuttings will benefit from the protection of a cold frame. Even though plummeting temperatures do little harm to most fruit bush cuttings, a cold frame will physically stop foxes and other wildlife rummaging around your hardwood cuttings. And fewer disturbances allow more roots to grow.
There are plenty of options when it comes to deciding on which cold frame to buy. The trick is to buy the largest one you can afford both wallet-, and space-wise. Remember you will need to get access from all around the frame, or at least three sides, so consider that before buying. Another important factor to consider is the weight of the cold frame. To be honest, I’ve known the cheaper, lighter versions blow away in winds the breezier side of gusty. Heaven knows what would happen if a real hurricane struck. Wooden frames are good (look for FSC to ensure good wood management) and aluminum or plastic frames cheap are light. However, most of the weight is in the frame and comes from the glazing. Horticultural glass is good but can break if your children aren’t too accurate with the football. Plastic is cheaper, lighter and takes some bashing. It’s also common for the plastic to be twin walled and that means great insulation.
The lids (or lights, or simply the top of your cold frame) can be hinged opening or sliding. Sliding lights are less prone to being whipped up into the air on windy days but the hinged ones do offer some protection for your cuttings and seedlings from the rain. Whichever you choose make sure you open the lights on warm days as diseases can quickly get growing in the warm, moist atmosphere of a well stocked cold frame.
Now, I’ve used a few cold frames in my time and seen the lighter ones blown across allotment sites, seen some smashed by an errant cricket ball (it was a good shot though!) and even not seen one disappear from my plot due to thieves (it must have taken some lifting – complete with seedlings) so my advice is to buy big, buy heavy, pin it down and never look back again. Gardening just won’t be the same.