Weed control, then, is an operation that should be performed in some form throughout the entire life of a Christmas tree planting. A typical weed control program using herbicides and mowing as the primary weed control techniques might be as follows:
Planting site mowed while the weeds are still active in late August to early September. About a week later, three foot wide strips are sprayed using a contact herbicide where the tree rows will be planted.
In spring, after the frost is out of the ground and before planting seedlings, a residual herbicide is applied to the three foot wide strips. With many residual herbicides, this application could also have been made the previous late October to mid November before the ground freezes.
During the growing season, areas between rows and between trees are mowed several times.
Intensive weed control around young trees using residual- herbicide.
Weed control between rows and trees by mowing.
Weed control between rows and trees by mowing.
Other control techniques could obviously be substituted in this program (e.g. the intensive weed control could have been accomplished by rototilling or mulching). Also, the exact weed control program varies with the particular grower, site and species of tree. For example, on some sites, intensive weed control may be needed only the first two years for Scotch pine, while on other sites it might be needed the first four years. On similar sites, Douglas-fir or Fraser fir may need intensive weed control longer than Scotch pine. Many growers use intensive weed control annually throughout the entire rotation; others practice intensive weed control until the seedlings are established and every other year thereafter. Still others intensively control weeds during the seedling establishment period, then once at about mid-rotation and again the year of harvest. The grower must become the expert for his plantations to develop the weed control program that best achieves his objectives. This cannot be over-emphasized if highest quality Christmas trees are to be produced at the lowest cost.
Throughout this discussion specific herbicides have been presented as examples, but no recommendations have been made. Nor has a complete list of herbicides labeled for use by Christmas tree growers been presented. Labeling of a herbicide is subject to change on relatively short notice, making such a list obsolete. State extension foresters are probably the best source of information on herbicides currently labeled for Christmas trees. In some states, service foresters and "rowers' associations can also assist.