Last year was an extremely good year for top-fruit, at least in my neck of the woods. On the Plot #79 allotment orchard, in the heritage orchard at Ordsall Hall where I work, and up at Holly Mount Community Orchard where I’ve done a few volunteering sessions, the trees were laden with fruit, branches bending under the weight of all the apples and pears, and the harvest was mighty1It was almost as if the trees knew we were all having a bit of a shit year – please excuse the massive understatement if it applies to you – and were trying to cheer us up with lots of extra fruit. Not that this is in any way what was actually going on, of course..
The glut was most likely triggered by a near-perfect pattern of weather last year: a hot and dry spring encouraged the pollinators, leading to high rates of fruit-set. And then the weather was cooler and wetter through the summer, providing the moisture and mild temperatures that allowed the fruit to develop without being starved or badly sun-scorched2Of course, many other factors could and will have played a part as well – fruit growth is the end result of an incredibly complex series of causes and effects – but the weather is the most likely principle agent of success..
This year: not so impressive. Fruit set on the trees that bore the heaviest crops last year is noticeably reduced. At the Hall, the ‘Kewsick Codlin’ and ‘Blenheim Orange’ trees in particular seem to be having an ‘off year’. I’d estimate they’re carrying around 10% – 20% of the total yield compared to 2020. The pear trees on plot #79 are distinctly sparse this year3Although that could be something to do with a possible fireblight infection – I’m investigating further… as well, and our next-door neighbour’s ‘Crispin’ apple tree, which is very mature and quite large, has barely two-dozen fruits that I can see, whereas last year it produced hundreds and hundreds.
If your trees are in a similar state, then the important thing is not to worry. This is all perfectly normal, a natural part of the tree’s lifecycle. It doesn’t mean that your tree is dying, or that you haven’t fed or watered it enough, or that the goddess Pomona no longer smiles on your orcharding efforts4You did make all the appropriate sacrifices at the appointed time, didn’t you? Good. You’ll be fine..
Again, the main reason for the reduction is likely to be the weather. An early warming in March and April led to blossoms opening, just in time for late frosts in May to cause a lot of damage and discourage pollinators. Then the very hot, dry June that we’ve just experienced may have caused a heavier-than-normal ‘June drop’, whereby the tree naturally sheds excess fruitlets that it is unable to provide enough water and nutrients to sustain.
But another factor could be that the trees are having an ‘off’ or ‘rest’ year after putting so much energy effort into fruiting in 2020. The (hugely simplified5I do intend to review a vast amount of research into top-fruit growth, development and morphology and write up a whole series of blog posts on various subjects, but that will have to wait for the long weekend mornings of winter when there’s not so much allotment work to do…) explanation for this is: most top-fruit trees initiate next year’s fruit buds at the same time as the current crop of fruits are developing. By ‘initiate’ I mean: trigger a highly complex series of genetically-driven chemical reactions that induce some buds to develop into the larger, more pronounced potential fruit buds that you can often see on the bare stems of fruit trees in winter.
These potential fruit buds are protected by thick casings which shield them through the winter months. The lower temperatures of winter then help to trigger further changes to the proto-organs contained in the buds, in a process called ‘vernalisation’ (see my post on ‘chill hours‘ for a quick explanation) and if these changes progress to a certain point, the bud will develop into blossom in spring, and if pollination is achieved then fruit will follow.
As I mentioned, next year’s fruit buds are being initiated at the same time that this year’s fruit is growing. So if a tree is carrying a lot of fruit, then most of the energy available to that tree – which is determined by the tree’s ability to photosynthesise, which in turn is determined by (amongst many other factors) the volume of water and nutrients that the tree can draw up through its roots and the amount and intensity of sunshine the tree’s leaves are exposed to – will be devoted to current fruit growth and ripening. After all, the fruit carries the tree’s seeds and seed production is, for the tree, the whole point of its existence. Delicious apples or pears are just the vehicle by which those seeds are distributed far and wide6Distributed by bears, originally. And horses. And dung-beetles. Humans have come late to the top-fruit party, although of course we have a tendency to think that everything is here mainly for our benefit….
This will mean that there’s less energy available for initiating next year’s fruit buds, and so fewer fruit buds will be initiated. And if they’re not initiated this year, they can’t develop into fruit next year. The reverse, of course, is also true. In an ‘off’ year, the tree has more spare energy to devote to initiating next year’s fruit buds, and this in turn is likely trigger to another fruit production boom.
If a tree has a series of boom years followed by bust years, then it can be said to have entered a ‘biennial bearing’ cycle. I read somewhere7Although of course I didn’t make a note of the exact reference, so I’m afraid you’ll have to take my word for it until I find it again… that this is the normal and natural state of affairs for most fruiting trees. Producing masses of fruit one year and then ‘resting’ the next allows the tree to repair or re-grow damaged limbs8Bears aren’t always the most careful of fruit harvesters. and grow out into available space, as more of its available energy can be devoted to stem and shoot growth if there are fewer fruits to sink that energy into.
Of course, from the point of view of the orchardist, a biennial bearing cycle can be far from ideal, as it might mean too much fruit one year leading to excessive wastage, and then not enough to eat, sell or turn into juice and cider the next. Although if you have a lot of trees then there might be enough of them on alternate biennial bearing cycles – half the trees booming one year, half the next – that it might not be a huge problem9.A half-and-half biennial bearing cycle could even be beneficial if, for example, you’re producing cider and would prefer to have gluts of particular varieties every other year so you can produce volumes of single-variety ciders and mature them for longer.
The way to manage top-fruit trees to help them avoid a biennial bearing cycle is to practice fruit thinning. I’ve written about the reasons for, effects and methods of fruit thinning once or twice already, so I won’t cover everything again here.
The TL;DR version of the benefits of fruit thinning: reducing the energy drain on the tree this year helps make more energy available for initiating next year’s fruit buds. It also means that this year’s fruit will grow, develop and ripen better, leading to a higher quality harvest. Annual fruit thinning is therefore vital if you want to grow good apples, pears and other top-fruit this year and next, and for all the years of your tree’s lifespan10This is another good reason for growing your orchard trees on dwarfing or semi-dwarfing rootstock, because you can’t thin fruit clusters that you can’t reach, unless you apply agricultural-grade fruit thinning sprays..
So, to summarise: don’t worry too much if your otherwise healthy and relatively pest- or disease-free tree is low on fruit this year after a magnificent showing in 2020. But do remember to keep an eye on the fruit load in 2022, and if you see a lot of fruitlets developing then get out there with your sharpest, cleanest secateurs and thin as many fruit clusters as you can reach down to one or two fruitlets (see my post ‘How To: Thin Out Apple and Pear Fruitlets‘ for an overview). You’ll be glad you did if it means you get to enjoy a good harvest of high quality fruit in 2022 and another in 2023, and 2024, and 2025…
If you’ve got any questions about biennial bearing and fruit thinning, or would like to share your own success stories, please do leave a comment via the form below (if it’s your first comment on the site it might take me a little while to moderate an approve it, but after that you’ll be able to comment freely) and I’ll respond to any queries as soon as I can.
Footnotes
- 1It was almost as if the trees knew we were all having a bit of a shit year – please excuse the massive understatement if it applies to you – and were trying to cheer us up with lots of extra fruit. Not that this is in any way what was actually going on, of course.
- 2Of course, many other factors could and will have played a part as well – fruit growth is the end result of an incredibly complex series of causes and effects – but the weather is the most likely principle agent of success.
- 3Although that could be something to do with a possible fireblight infection – I’m investigating further…
- 4You did make all the appropriate sacrifices at the appointed time, didn’t you? Good. You’ll be fine.
- 5I do intend to review a vast amount of research into top-fruit growth, development and morphology and write up a whole series of blog posts on various subjects, but that will have to wait for the long weekend mornings of winter when there’s not so much allotment work to do…
- 6Distributed by bears, originally. And horses. And dung-beetles. Humans have come late to the top-fruit party, although of course we have a tendency to think that everything is here mainly for our benefit…
- 7Although of course I didn’t make a note of the exact reference, so I’m afraid you’ll have to take my word for it until I find it again…
- 8Bears aren’t always the most careful of fruit harvesters.
- 9.A half-and-half biennial bearing cycle could even be beneficial if, for example, you’re producing cider and would prefer to have gluts of particular varieties every other year so you can produce volumes of single-variety ciders and mature them for longer.
- 10This is another good reason for growing your orchard trees on dwarfing or semi-dwarfing rootstock, because you can’t thin fruit clusters that you can’t reach, unless you apply agricultural-grade fruit thinning sprays.