OVER FOUR MILLION FAMILIES in California enjoy fresh evergreen trees in their homes every Christmas. Few people realize what efforts have gone into producing a tree that will maintain a vigorous, healthy appearance over the long Christmas holidays. Thousands of acres of trees are thinned, pruned, sheared and fertilized before harvest. Approximately a million of these trees are thinned annually from the high elevation forests of California. Large timber companies and other forest landowners have given long-term management and harvesting leases to Christmas tree operators to insure an annual income from their forest lands. Many forest landowners also manage and harvest trees from their lands on a sustained yield basis. The success of the Christmas tree industry and its $20 million payroll depends on the high quality of properly harvested trees. The date a Christmas tree operator selects to start harvesting, plays an important role in determining freshness.