Causes of alternate bearing
There is no one cause of alternate bearing, instead, it is down to a multitude of problems, that mainly stem from neglect. The following lack of maintenance can lead to a biennial bearing for your trees:
- Receiving insufficient moisture or watering
- Overwhelmed by weeds
- Unfertilised or not having enough nutrients
- Late frost during the springtime
Common trees that suffer from biennial bearing
While any plant can suffer from alternate bearing, it is most common among fruit-bearing trees, including:
Prevention of alternate bearing
Prevention is the only way to get rid of alternate bearing in your fruit trees, and even then, using these techniques will not guarantee the ‘biennial curse’ will not continue!
Pruning
After a light or bad crop, pruning back your tree will mean less flowering and, therefore, a less abundant crop the next year. While this may result in two years of fruit scarcity, it will help break the alternation cycle.
Jon Lamb from the Good Gardening podcast recommends pruning back your fruit trees in winter.
Thinning
Thinning out the fruit from your tree in the weeks after initial flowering should also help break the biennial cycle. As Jon Lamb explains, “During a heavy crop year, reduce the number of fruits and fruit bunches 6 to 8 weeks after flowering.”
This will promote flower formation over heavy fruit production, meaning that your tree will be perfectly abundant by the time next year comes around! You can thin out your fruit tree manually or through chemical agents, which is how large orchards and fruit farms usually operate.
Crop nutrition
Finally, having good crop nutrition and properly maintaining your fruit trees will mean that an alternate bearing cycle may never eventuate in the first place.
If you have a particularly heavy crop year, Jon Lab recommends a full application of fertiliser immediately after harvest. He says, “Make sure this is watered well into the topsoil beneath the trees and keep them well watered through autumn.”