Winter has finally arrived and so too the first frost, gone are the foliage of the NZ yams, nasturtiums and late potatoes.  In the Upper Mountains we know it all too well; but in fact frost can happen anywhere in Australia even the tropics. The Atherton tablelands can experience early morning frost even when the daily Temperature climbs to 21ºC in winter.  Sitting here, in mittens next to the heater typing away I would be happy with half that warmth as the day progresses. I have only to look out the window and see how the lettuce are huddling down and refusing to grow, as bigger leaves would mean frost bite.

So I have to concede that as we try and push the boundaries of what we can grow at our dizzy altitude, we need to recognise that for some plants protection will mean the difference between life and death.

By definition a frosty night is a “clear and still winter night where sounds seem to travel for miles and the earth beams it radiant heat back to space, without a cloud blanket to keep any heat in the moisture at ground levels freezes and forms frost”.  As the cold comes up from the ground the cells inside many plants freeze and burst as the water inside them expands to form ice.  Damages to the cells can also occur when the ensuing sun at day break melts the water so fast that the cells walls can’t respond quickly enough to these changes in pressure, in some cases the plant never recovers. 

In days gone by farmers would light fires in their orchards to create an inversion layer of smoke to keep heat in, much as clouds do; or they would put on water sprinklers to somehow stop the frost forming. I have tried spraying my lettuce lightly to thaw then out slowly and it has seemed to work if I can get up and out early enough, and fortunately for me, spinach and kale don’t seem so sensitive. For several years now I have potted some of my hardier veggies and rehoused them in a sheltered spot till summer, and then I plant them out again. In my case a hot house but prior to its purchase I would just bring the pots close to the house and make a cold frame using window glass as a cover. This way I manage to turn some of my annuals into perennials one of Bill Mollison’s concepts; eggplant and chilli seem to respond well to this treatment.

I have also discovered that frost protection can be as simple as throwing a blanket over your plants or if you want to protect a plant for several years a simple structure can be built around it that can wrapped in insulating materials. I have seen photos from Europe with trees shrouded in straw and bracken within a wire structure. I haven’t tried protecting mature trees, but I have used home-made chicken wire cylinders covered in bubble wrap around my newly planted ones until the mature and become more frost resistant. I’ve been told that a ‘hat’ can be placed over it during the night and removed during the day, but I doubt I would ever remember…It works for container plants as well.

Lizzies cold frame              Wire structures over containers can be covered  

 Bubble wrapped cylinder covering lemon-grass       Rowe’s old hot-house

I guess the moral is that if the air is still and the sky clear, cover your frost sensitive plants; it is always better to be safe than sorry.