Nursery Tree Quality

A problem in Pennsylvania orchards is the presence of a virus called stem pitting, which causes early death in peach trees. In response to the problem, the Pennsylvania Department of Agriculture (PDA), Bureau of Plant Industry, has established a virus-free certification program in cooperation with Pennsylvania nurseries. The program seeks to provide and maintain virus-free sources of budwood for state nurseries and growers. Pennsylvania nurseries can therefore offer two grades of trees: Penn Standard and Penn Premium. Penn Standard trees are certified for virus-free budwood, but not for virus-free rootstocks. Penn Premium trees are certified for both virus-free budwood and rootstocks.

Surrounding states may also have certified virus-free trees. Growers are encouraged to take advantage of these programs. When ordering trees ask the nursery if it belongs to such a program.

Tree caliper is another measure of nursery tree quality. Trees of a larger caliper--greater than 5/8 inch in diameter--often are not suited for today's orchards. The larger a tree's diameter, the less choice you will have in selecting scaffolds. Thicker trees tend to be taller, and it may be difficult to force branches low to the ground. In addition, after a larger-caliper tree is headed back, Cytospora canker may infect the large wound area, eventually resulting in the tree's death. Small-caliper trees, less than 1/2 inch, are easier to train for certain production systems, such as the central leader, but they need extra care the year of planting to prevent competition from weeds.