Colonnade apple trees are relatively new on the fruit tree scene. They were introduced to the United States in the mid 1990's. They grow well in USDA Hardiness Zones 4 through 8 and ripen in September. Unlike most apple trees, they are now rounded in shape. Instead, they grow upright and narrow, making this apple variety perfect for tight gardening spaces. Short spurs grow along the main trunk, whereas other apple trees develop horizontal branches. You can't plant just one, however, because they are not self pollinating. Plan to grow at least two colonnade apple trees for cross-pollination.
Buy two colonnade apple saplings from a planting center. There are several varieties including crimson spire, emerald spire and maypole flowering crab apple. Check the saplings over to make sure the root system looks healthy. Also check the leaves for spots or blotches, which are signs of an infestation.
Fill two planting containers halfway with a good potting soil mix. Press it down to remove air pockets.
Cut the colonnade apple trees out of their plastic containers carefully. Break up the root mass gently by hand to separate tangled roots.
Set the colonnade apple trees in the center of the containers. Backfill with potting mix around the roots, until the container is full. Tamp it down gently but don't pack the dirt too tightly.
Water the colonnade until the soil is moist. Insert a finger several inches into the soil to check to make sure the water reaches the roots.
Put the containers somewhere they will get full sun. Six to eight hours per day is ideal. If necessary, move the containers to correspond with maximum sun exposure.
Water the trees whenever the soil fees dry to the touch. Apple trees are not drought resistant, so they need moisture.
Fertilize colonnade apple trees two to three times annually. Wait until after the first three months have passed to do the first application.
Prune the colonnade trees each winter, before spring growth starts, to remove dead and damaged branches. Also snip off stems that are growing out horizontally, ruining the shape of the tree. Prune extra long stems back to three leaves because this will promote new buds and growth.