Frost and fruit trees

The question of frost and fruit trees often comes up when people are deciding which fruit trees to order for their garden, so we thought we’d clarify the issue this week, particularly as we’ve had the first few frosty mornings here on the farm.

A frost near the apricot orchard
A frost near the apricot orchard

Winter frosts are not a problem – in fact most deciduous fruit trees need a certain predetermined number of hours of cold each year to help them set fruit (this is called chill factor, and is a separate issue to frost – find out more about both chill factor and frost in this online short course).

Frost is only a problem for your trees in spring, and only if there’s a frost when the trees are flowering, or when the fruit is tiny just after flowering.

Spring frosts while trees are flowering can sometimes cause damage
Spring frosts while trees are flowering can sometimes cause damage

The hierarchy of frost-sensitive fruit trees is that almonds and apricots are most frost sensitive, then cherries, peaches and nectarines, apples, plums, and pears, in that order.

That doesn’t mean that apples, plums and pears don’t get frost damage though, they can. This is a photo of a typical ‘frost ring’ on a tiny pear – damage caused by a frost when the tree was flowering.

A frost ring on a pear
A frost ring on a pear

If you get bad frosts and don’t have a way to protect your trees in spring, then your apricot trees are likely to not bear fruit very often because the flowers will be burnt off by the frost.

This means they then put all their energy into growing wood instead of fruit, and you can end up with a very big tree!

A very large apricot tree
A very large apricot tree

So what can you do?

First, it’s important to know how frosty your place is, and where are the most vulnerable spots, so the next time you have a frosty morning, head outside nice and early in the dressing gown and gumboots, and really have a look at exactly where the frost is lying.

Then, try to match the trees you’d like to grow to the available micro-climates (saving the least frost-affected spots for the most frost-vulnerable trees).

Next, think about how you can create or enhance the microclimates
with plantings or infrastructure to create protected pockets.

Other things you can do include:

  1. Planting the most sensitive fruit trees in pots so you can shift them to protected spots in spring;
  2. Use frost cloth (or even old sheets) when frost is threatened (but remember to take it off again the next morning).
Frost on the soil
Frost on the soil

When you consider all the options available to you, it’s really surprising just how much you can do to provide the right habitat for lots of different fruit trees, even if they’re a bit outside their normal comfort zone.

This tamarillo tree is a great example – it’s absolutely thrived in a climate that is supposedly far too cold for it, by planting it in a sheltered spot right next to our shed wall.

A fast-growing tamarillo tree protected from frost by planting next to the shed
A fast-growing tamarillo tree protected from frost by planting next to the shed

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