Canada has made great strides in its research and development efforts to increase the vigor and growth rate of harvestable trees, to improve their wood quality and to protect them from diseases and insects through the use of means more environmentally-acceptable than synthetic chemical controls. Using nature's best Traditional tree breeding methods have been used in many countries for years now. Historically, stands of these plus trees have been managed so that only the best are kept as sources of seed. But these seed stands generally contain a relatively small number of trees and thus the amount of seed that can be collected from them is limited. Trees produce flowers which, in turn, produce pollen.
Pollen is spread from flower to flower by such natural mechanisms as wind and insects.
This pollen carries the genetic material which determines a tree's qualities. This occurs because in the seed orchard environment only pollen from plus trees is mixing and there is minimal infiltration of pollen from surrounding, less desirable trees that could take away from the qualities for which these plus trees were initially chosen. Seeds from the offspring of these seed orchard-grown plus trees are being used to produce seedlings for replanting harvested forest areas that may not adequately regenerate naturally. Roughly 50 percent of the seeds and seedlings used for regeneration of harvested forest lands in Canada are derived from plus tree parents. Plus trees can also be reproduced from cuttings.