Apples and pears produce most of their fruit on small, fruiting branches called spurs. Spurs are small, slow growing, funny-looking branches. Make sure you don’t cut these cute little branches off when you are pruning, or you won’t get much fruit for a couple of years.
During the six weeks or so after blossom time, this year’s fruit start to grow on some spurs. At the same time, flowers for next year’s crop are being initiated in the buds of other spurs. Individual spurs cannot do both at the same time. This results in a phenomenon called biennial bearing, or producing fruit every other year. If you are growing apple or pear trees in your garden, you are likely familiar with biennial bearing. Most apple and pear trees will have a year with a big crop, followed the next year by a small crop. In some cases, biennial bearing is so severe that a tree will have a huge crop one year and no fruit the following year. This cycle can be initiated by many things, such as bad weather at blossom time or winter damage. Commercial orchardists spend a lot of effort trying to eliminate this tendency so that they can produce a dependable volume of fruit for the market each year. A year without fruit means a year without income for these businesses.
If there is fruit on most of the spurs of your trees in early June, it is a good idea to remove all of the fruit from half the spurs (approximately). This is called thinning, and will allow the trees to spend their energy developing flower buds on those spurs for next year. Another reason to thin your apples and pears is to increase the size of the fruit you leave on the tree. To accomplish this, fruit are usually thinned to one or two on each spur. Don’t be surprised if some of your fruit start to drop off your trees on their own in June; this is a natural shedding of weak fruit called June drop.
In the picture there are two spurs, one growing apples and the other with three visible scars where last year’s apples were attached. The spur with no apples is likely in the process of developing a fruit bud for next year.