by Hilary Rowley
Here in the south we can grow all sorts of fruit trees and shrubs, but that does not mean we can actually harvest fruit from them. Frost and cold winds are your enemy here, and apart from sensible placement of your fruiting plants, and barrier methods there is not much to be done. The frosts we are having lately will damage fruit and buds on a poorly placed tree. Imagine frost forming like water pooling behind a dam, or in a hollow. On a slope it will pool behind a wall or a hedge, or at the bottom of the hill. The flat land in Waitati gets much harder frosts than on the hills. Movement stops frost from occurring so on a slope the air is flowing down hill and as long as there is nothing to dam it there will be less frost. A fast-flowing river will stir up the air and create areas of less frost. In Central Otago some orchards use big propellers on frosty nights to stir up the air. Because the sea is such a big body of a certain temperature, places close to the sea get less frost.
Apples and pears, and plums are the toughest and can be planted in the less favourable places in your orchard, like at the bottom of the hill, or behind the house, while more delicate trees like peaches, nectarines, cherries and apricots should be further up the hill. It's a frosty night as I write, and we have covered our Moorpark apricot with frost cloth. I just lift it gently over the tree using long bamboo sticks, and can take it off again in the morning. This would not be possible if we had let the tree get too tall, but it's short and wide, so it works. The lemon trees get a sheet thrown over them on frosty nights and removed in the morning. Damage is also done by the sun hitting frozen growth on a fruit tree and thawing it too quickly. My really old Victorian gardening book states that this can be prevented 'by thoroughly watering the blossom or young fruits with cold water, applied with a garden engine, in the morning before the sun shines on them'. Now there is something to do before you go to work on a frosty spring morning. Another method much loved in 19th century European gardens was to grow trees against a sunny brick or stone wall, so the heat absorbed during the day would be released at night. I think a method of solar-powered frost fighting would be sensible, as it's usually a frosty night following a sunny day,so your solar-powered propellers, or solar-powered heating system would be at full strength. I don't think these have been invented yet, but would be fun to experiment with.
Or, of course, you could not intervene at all, and in some years have no fruit on your delicate varieties and, if you are lucky, in some years have lots.