The initial cost of columnar trees is usually a tad higher than standard fruit trees. Lacking the expansive side growth, it also produces less fruit than your normal garden variety of fruit tree. They have however been proven to be productive for several decades.
So far as growing a columnar fruit tree - other than pruning, the same care that would be associated with standard fruit trees should be applied. Hardiness zones, sun -shade requirements, temperature range, soil fertility, and pollination requirements do not change simply because of the trees growth habit. Fruits such as apples still require at least two distinct varieties to set fruit, grafted trees would be needed if you only plan on growing one.
Spacing varies, depending on fruit tree variety and the effect you wish to attain. Growing as a hedgerow you should take into account the mature expanse of the tree - which is 2-3 feet for most apple varieties, and a bit more for some stone fruits such as peaches which an be 4- 5 feet. Allow for adequate air circulation when determining spacing. So basically a tree with an anticipated spread of 3 feet should be spaced 3.5 to 4 feet apart.
If scattering your trees to various locales in your landscape remain aware that Fruit trees requiring cross pollination should be planted relatively close to one another in order for pollinating insects to traverse the buds of both.
For trees grown in containers spacing is not an issue as they can be easily moved and shuffled about as needed.
Pruning on trees that are true columnar fruit trees should only be done to remove damaged branches. If you have a tree that is not a true columnar tree and are attempting to train it to grow in a narrow column - that's another topic all together.
Minarette Fruit Trees
Minarettes are not Colonnade or Columnar Fruit trees, they as standard apple or pear trees that have been trained and vigorously pruned to attain a columnar effect. This is generally done with Apples, Pears and figs. It is possible to train stone fruits as minarettes but is a tad more problematic. The growth habit of stone fruits is not as well-suited to the steady consistent pruning that is needed to maintain the columnar effect. There are stone fruits, particularly Peaches bred as columnar, their spread however is not as compact as the apple varieties.
Cordon Fruit Trees
A cordon fruit tree, like a minarette is also not a columnar tree. It too has been vigorously pruned to concentrate fruit production along a central stem.
The difference between cordon and minarette is that the angle of the cordons branches match that of the stem. The branches grow vertically up along the central leader.
The quality of fruit grown on a cordon is generally superior to minarettes and some say to columnar. Sunlight more readily penetrates the canopy and side foliage of these trees which aids in the ripening process and allows the fruits to concentrate more natural sugars.
Both cordons and minarettes will revert to normal growth habits if pruning is not continued, they are high maintainence.
Indoor Fruit Trees