Your nursery can help you decide. Although you do not plant most wildland trees during the summer you should make sure you have ordered your trees for the season by early summer. Many people who wait until fall to find available trees just might not find any seedlings. Always order your seedlings as early as you can. Planting urban trees is a little different.
Any season is OK for planting balled or burlaped trees.
For simplicity, I want to divide planting into two categories - horticultural and wildland planting . Horticultural tree planting is geared toward urban situations where landscaping is of primary concern. Where higher valued seedlings, saplings, and trees are planted to enhance property, more effort should be spent on each individual tree. Kim Powell, Extension Horticultural Specialist, explores the types of trees available for transplanting and gives tips on purchasing, planting, and maintaining tree transplants . Wildland planting, however, is done over a much broader area.