Caring for apple trees in Colorado is not much different from maintaining apple trees in other locations, with the exception that as a semi-arid state, Colorado gets less water than some other apple-producing areas. By properly pruning and caring for your apple tree or orchard, your tree should produce fruit for many years. Apples grow in many parts of Colorado, including lower altitudes on both the eastern and western slopes of the Rocky Mountains.
Prune your apple tree in the winter when the tree is dormant, if pruning is necessary. Pruning is most often done to manage tree size and to encourage fruiting and directed growth.
Cut the previous year's growth to about 1/4 inch above a leaf growth node when pruning. Trimming further above this location will leave wood in place that will consume tree resources, but not contribute to tree growth. Prune to open up the tree to allow sun to reach the inner parts of the tree. Try not to remove more than 1/3 of the previous year's growth.
Remove any dead or dying branches. For branches smaller than about 1/2 inch, use pruning shears. For larger branches, use a pruning saw.
Watch for black marks on the branches that could indicate fire blight. If you see these, cut back well below the black marks to remove this bacterial disease.
Fertilize your tree if you get less than 12 to 24 inches of new growth per year. If your soil needs fertilizer, add 1/2 pound of 10-6-4 fertilizer for every year of tree age up to 15 years, or 7.5 pounds. Scatter the fertilizer under the tree and water thoroughly to encourage movement down to the roots.
Give your apple tree 1 to 2 inches of water whenever the top 1/4 inch of soil feels dry. How often this is will depend on your location, the natural rain, and time of year.