Protecting Fruit Blossom from Frost

19 April 2018, written by Ann Marie Hendry

Two words plunge icy daggers of fear into any fruit gardener’s heart: Late frost!

Most fruits need several weeks, if not months, to reach their juicy, mouth-watering peak. To do that they need to be quick off the mark, pushing out flower buds earlier than many other plants would dare. But sometimes spring can really kick you in the teeth!

Remember all that mulching, feeding, watering and pruning you did? A single night of freezing temperatures after your fruit’s blossom has begun to form can undo all your hard work in one fell swoop. Frosted blossom can result in little or no fruit, so it pays to take action to protect your lovingly grown fruit trees and bushes from winter’s last laugh.

Planning for Frost in the Fruit Garden

Cold air sinks – which explains why my feet are always cold – so if your garden has low spots cold air will pool here. The same holds true if your garden is sloping and ends in a solid barrier such as a wall or fence, or even a dense hedge. If you must grow fruit in such a location, consider opening up the boundary by making a gap, or thin the base of hedges to allow cold air to drain away. Avoid growing lower-growing fruits such as gooseberries or strawberries in these areas if at all possible, as their blossom will be more susceptible to being frosted than taller fruit trees.

“Poorly-fruiting — Frosted blossoms can result in few or no fruits forming

Sun-facing stone or brick walls on the other hand are a boon, soaking up heat during the day and releasing it at night. Train fruit against the wall to benefit from this radiated heat, which could be just enough to save those precious blossoms. This is particularly beneficial for the less hardy fruits such as peaches, cherries and apricots.

Keep the area around the trunk of the plant weeded and either bare or mulched. Grass and other vegetation makes it harder for warm air to rise up out of the soil, so keeping it bare could make the difference between flowers being frosted or escaping unscathed.

Wet soil is also said to radiate more heat than dry soil, so it may be worth watering when a frost is forecast.

Frost-tolerant and Late-flowering Fruits

Some fruits are less likely to be affected by late frosts by virtue of being slow starters. Raspberries and blackberries for instance tend to flower after the risk of frost is past, as do acid cherries and most modern varieties of blackcurrant.

“Blueberry — Blueberry flowers open at different times so some may escape being frosted

The flowers of blueberries and strawberries don’t open all at the same time, so don’t despair if a late frost catches some of the flowers – more are likely to follow, and will hopefully escape winter’s clutches.

Choose late-flowering varieties if you can. Some detective work may be required as the flowering time is not always specified when buying fruit plants, but a good tip is to choose varieties bred in your area if possible. That way you can be reasonably sure that they’ll perform well in your garden’s typical conditions.

Covering Blossoms to Protect Against Frost

Even with the best planning, late frosts can still be a problem in colder areas. Covering up fruit trees and bushes can help to keep the blossoms just warm enough to make it through.

Clearly, large trees cannot be covered up. On the plus side, flowers higher up on the tree may remain warm enough and go on to produce fruits even if the blooms on the lower branches get zapped.

“Peach — Make a protective tent over your fruits to protect their blossoms

Fruit bushes, very dwarfing fruits trees and wall-trained fruits are a little easier to protect. Drape two or three layers of row cover fabric over your plants, or use plastic, sheets or any other light material you have to hand. Make sure it extends to ground level to trap warmer air next to the tree.

Strawberries, being compact and ground-hugging, are the easiest of all to protect. Simply lay your preferred cover over them, or use tunnel cloches or individual cloches.

To prevent the cover from sitting directly on top of blossoms, and to help avoid pointy branches poking a hole in the material, suspend your cover on canes or stakes. Cane tips can puncture the material, so place something over the end – old tennis balls work well. Don’t forget to remove covers during the day to let insects in to pollinate the flowers.

Do you have any tips for protecting fruit blossoms from frost? Share it with us by leaving a comment below!