Marcelle NankervisFrosty morning

Frost damage on ornamentals is bad, frost damage on vegetables is devastating. Last week’s frosts were so severe that icicles had formed on the timber surrounding each of my vegetable beds, and the edges of most plants were frilled with icy crystals.

For the first time ever, I was worried about the impact of the frost on my garden. Our vegetable garden supplies most of the vegetables for our family, so huge losses will put a hole in my supply and I really don’t want to buy produce from the shops.

I had prepared for frosts by mulching with sugar cane and by applying seaweed supplements to the garden, but only poly-tunnels would have prevented this last frost from mutilating the garden.

As the morning sun completed the damage, I frantically looked around for some black plastic to cover the garden beds but I was simply not prepared for this kind of frost.

To my surprise, the lettuces were all OK. Not one sign of obvious damage. The potatoes on the other hand have completely disappeared … not even one leaf or stem is left above the soil. Resisting the urge to remove any damaged foliage, my thoughts turn to frost and what I can do to prepare for more cold mornings in the future.

So how does the damage occur?

The extreme cold freezes the plant cells causing crystals to form and like a sealed bottle in the freezer, the cells expand, causing the cell wall to rupture. Just like that bottle in the freezer, if you thaw it gradually, you may save the bottle, but if it defrosts too rapidly, it will burst. So the trick to minimising damage is to either prevent the plants freezing, or if they do freeze, you need to defrost them slowly. Black plastic over the plants helps to prevent the morning sun defrosting them too rapidly.

I have been establishing most of my potager by direct seeding, and after last week, I can finally see the true value of a glasshouse. My next mission is to find the right poly tunnel set up for our windy farm. It does not need to be big, but it does need to be sturdy. I had been avoiding these because most of the garden is set up to function automatically. In a glasshouse, I will need to water the seedlings myself … but that is something I am willing to do for the long term gain that this short term protection will offer. Then in spring, after the majority of frosts have passed, I will be able to plant out strong home grown seedlings and hopefully get a jumpstart on my next crop.

Living on the Mornington Peninsula, only 10 minutes from the beach, it is easy to assume that we have a frost-free maritime climate. I can assure you, this is not the case. But at least now I know what I need to do to be prepared for what the season throws at me and my seedlings.  

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Marcelle Nankervis

About Marcelle Nankervis

Garden journalist, author of Plants for Australian Dry Gardens and Smart Gardening – grow your own fruit and vegetables, contributor to many garden magazines. Mornington Peninsula, Victoria

One thought on “Frosty morning

  1. That’s terrible, Marcelle. Frost can be one of the most devastating things visited upon gardeners by mother nature.

    Mulching is a tricky one, as most frosts will be more severe on mulched surfaces than unmulched surfaces. In winter mulched beds don’t allow heat to penetrate into the soil. This solar heat builds up a storage bank in the soil that is then radiated out at night, discouraging the formation of heavy frost in the wee hours. Beds that are mulched are more severely frost affected because they discourage heat movement through the soil-plant system over the course of a day/night. Of course, not mulching your beds in winter is by no means a guaranteed way of avoiding frosts, as severe frosts will still form on bare surfaces. Knowing this I still ask myself every year; to mulch or not to mulch? I guess the non-mulching practice as a means of avoiding frost only works for light frosts, which yours, by the look of it, was almost certainly not!


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