How to summer prune apple and pear trees.
Gardening is full of sayings about what to do and at what time of year – start box hedge clipping on Derby Day, the Chelsea chop for herbaceous plants and shallots should be planted on the longest day and harvested on the shortest. One we use constantly here at the nursery is when to summer prune apple and pear trees – the answer is always ‘Second Sunday in August’. Giving such as specific date invariably raises a smile and hopefully makes it easier to remember, but the middle of August is the perfect time to summer prune all apples and pears, whether growing as free-standing trees or in trained forms such as cordons, espaliers and fans. We’ll look a little bit at the history of summer pruning, the theories as to why it should be done before finally explaining exactly what you need to do to your own trees.
Before the 1890’s, summer pruning of fruit trees was unheard of. All pruning was carried out in the winter months. However around 1898 a young man called Louis Lorette noticed that trained trees which had been pruned each winter produced a lot less fruit than standard trees which had been left unpruned. He started a series of experiments at the Practical School of Agriculture in Wagonville, France and proved that apple and pear tree buds formed at the base of a branch are more productive than those formed further up the branch. He wrote an article for the French gardening magazine ‘Jardinage’ in 1912 describing his new method, which did away with winter pruning and instead relied on pruning every 30 days from the middle of June onwards.
The general idea behind this radical new approach was that it encouraged the dormant buds at the base of branches to quickly form fruiting spurs. Traditional winter pruning was shown to encourage growth at the expense of fruit – great in the early years when the goal is to establish a good branch framework, but not so good once the tree had become established.
Over the past 100 years, studies have shown that this system does indeed increase fruit production, but with some important considerations. The main one for UK gardeners is that this system only works in certain climates – ideally with mild winters and long warm summers. Sadly, this is not the case for most of the British Isles! Instead, there have been various attempts at modifying the Lorette System so it works in our more inclement seasonal weather.
The current advice is to carry out winter pruning as normal - removing congested growth, dead and diseased branches - and to summer prune once in August. The middle of August is an ideal time to summer prune, as almost all the growth for the year is done by that stage. You can prune in June but the plant will still have the time and energy to regrow, so you will end up having to prune again later in the summer. Technically you should wait until the new growth has ‘lignified’ or become hard and woody before pruning, but for most of the UK the middle of August is a good rule of thumb. This summer pruning is especially useful for containing growth (where the tree is being trained as a cordon or espalier, for example, or outgrowing the space available), and still helps with Lorette’s original aim of increasing fruit yields.
How does summer pruning work?
Summer pruning takes energy out of a tree – it has just spent several months producing new growth which is then pruned off – and as such mildly stresses the tree. This stress encourages it to reproduce – the tree thinks it may be dying – and so produces new fruiting spurs for the following year. It’s similar to many other plants in the garden which respond to stress by reproducing – in dry weather you may well notice rhubarb plants producing flower spikes, or onion sets bolting. Summer pruning has the added advantage of improving light and air circulation for the current year’s crop – less shade will improve ripening and produce sweeter fruit.
Summer pruning fruit trees the easy way:
If you have carried out winter pruning the previous year, summer pruning is very straightforward. Simply reduce the length of all the new growth back to 3 leaves. It doesn’t matter if you are growing it as a freestanding tree, or one of the more ornate forms such as espalier, cordon or fan. As always, prune to an outward facing bud, angle the cut so any water droplets don’t collect in the bud axil, and use clean sharp secateurs.
If your winter pruning involved taking off mature branches, you may have provoke water shoots to grow away – several strong upright growths from the same point. This is a great time to remove them, as they are often unproductive, so with these shoots you can prune back flush with the main stem.
That is really all there is too it! Pick a warm sunny evening, take your secateurs out into the garden and snip away. And if anyone asks, you can casually mention how you are ‘Modified Lorette’ pruning – impresses every time!