Mature columnar apple trees average eight to ten feet tall and only about two feet wide. They can grow and produce healthy fruit for about twenty years. At this time, only columnar apple trees exist, but growers are working on making columnar versions of several other types of fruit, including pears and peaches.
Columnar apple trees have many advantages to the home gardener over their full sized counterparts.
First, they are smaller than semi-dwarf trees, and can therefore be grown in a smaller area.
They can work well as potted plants, making them very portable. Columnar apple trees are also early producers, and will possibly grow fruit on their first year.
There are some drawbacks to growing columnar apple trees. Since they are smaller, the amount of fruit produced by columnar apple trees is less than is produced by semi-dwarf trees.
The fruit is full size, and therefore some thinning may be required for the tree to be able to support the weight. Another drawback to growing columnar apple trees is that they are much more expensive than regular apple trees.
The extra work that goes into creating them can make them cost up to twice as much.