When purchasing or planting trees there are many things you should look for to ensure the long term health, structure and survival of your trees. If you go to the nursery you can pick and choose the best trees. If you are having a landscaper plant your trees, you should always closely inspect them before they are planted and reject undesirable ones. Trees will often appear healthy when first planted but years down the road after money spent on planting, maintenance and the trees themselves they can become seriously unhealthy, defective or even die. Pick the right trees from the start; include qualified arborists to help you! You will save lots of time and money and have beautiful healthy trees.
(Below is some helpful and detailed information from urbantree.org)
Shade trees grown in the nursery should have a strong central leader even if the leader will be lost at maturity. Temporary branches are important to trunk development because they build a strong trunk and root system. Good root systems start in the nursery at propagation in the liner stage and require attention each time a tree is shifted into a larger container. Installation contractors must provide simple root and shoot pruning treatments at planting to ensure that sustainable landscapes are created. The follow document have been developed to help industry professionals.
Specification Guidelines for Container-grown Trees for California. This document's intent is to help landscape professionals develop their own comprehensive and detailed specifications to ensure that they obtain high quality container-grown nursery trees. The document is also intended to help nursery professionals in their efforts to improve the quality of trees grown in California. These specifications can be modified for specific simulations. Recommendations for improvements to the document received in the past 5 years have been incorporated in this 2009 revision.
Strategies for Growing a High-Quality Root System, Trunk, and Crown in a Container Nursery. This document presents strategies to assist growers in producing trees that conform to the Guideline Specifications for Nursery Tree Quality. The strategies are based on most-recently-published and ongoing research, combined with the knowledge, skills, and know-how of both the practitioner and researcher, to produce high-quality root systems, trunks, and crowns. As research progresses and new strategies are developed, this document will be revised to incorporate state-of-the-art information.