Climate change increases the risk of damaged fruits and berries due to frost. As the climate gradually becomes warmer, fruit trees and bushes tend to blossom earlier in the spring – increasing the risk of frost related damage on infant leaves and blossoms. In later years, fruit farmers have experienced losses of up to 75 per cent of the production in certain fruit cultures due to frost.
Finding a sustainable solution
There are various ways of protecting early buds and blossoms from unexpected onsets of frost in the spring. One way is to spray them with water or natural oils. This creates an isolating layer that will protect the blossoms from being damaged by frost down to minus five degrees.
Another option is to spray with protective substances or biostimulants that will increase the plants’ resilience against frost during their growth. However, spraying requires vast amounts of water, and chemical substances do not necessarily constitute sustainable solutions – particularly not when it comes to ecological fruit farming.
Another option is therefore to look at the varieties of fruit that blossom later in the spring, says biologist Majken Pagter from the Department of Chemistry and Bioscience at Aalborg University. She does research in the relation between classes of fruit and frost tolerance.
- There is a huge difference between when i.e., different sorts of apples or cherries start their blossoming. Obviously, those that bloom later in the spring are better protected against frost damage. The drawback is that these sorts are not necessarily the ones favored by the farmers. This depends just as much on taste, yield, and many other factors, she explains.
An ancient technique with future potential
The solution to the problem can be to take a closer look at a technique that has been known for thousands of years. To achieve the best results, farmers very often graft their fruit trees. This means that that boughs from selected fruit trees are grafted onto the stem of another type of fruit tree.
This is typically done to harvest fruits from trees of limited height or trees that have a high resilience against diseases or funghi. But according to Majken Pagter, the grafting technique could potentially help fruit trees become more resistant against springtime frost.
- We know very little about how the base stem of a grafted tree affects the sensitivity towards spring frost – if it might influence when the tree blossoms or if that is solely down to the characteristics of the sorts that have been grafted onto the stem. This is something that we are very eager to learn more about in our quest to find a sustainable solution to adapting fruit farming to the climate changes, she says.