Maintaining good growth and survival of white pine will likely require control of competing weeds and shrubs and management of overstory trees (if present).
Control Competing Vegetation
Control vegetation for a distance of 3 feet around the tree. Grasses and weeds can be controlled by mowing, mulching, or using individual "weed control" mats. More extensive plantings may require the use of herbicides. Consult a forester or other professional on the kinds, timing, and application methods best suited for your situation. Shrubs can be controlled through hand-cutting or herbicides.
The shade from overstory trees should be maintained at about 50 percent (the percentage of the area where direct sunlight hits the ground). If shade becomes too dense, partial removal of overstory trees may be necessary. This can be done by carefully selecting and removing or girdling some of the overstory trees. Leave girdled trees standing to provide wildlife habitat.
Controlling Deer
White pine buds are a favorite food of deer and need protection to discourage deer browsing. This can be done using bud caps, repellents, or fencing.
A bud cap is a lightweight, 4" x 6" piece of paper that is folded in half and stapled around the terminal shoot and bud of the tree. Use at least three staples and catch some needles with the staple to help hold the paper in place.
Deer browsing of side branches is usually not detrimental to the health and survival of young white pine.
Bud-capping should be done in the fall before snow covers the ground. Trees can grow through the paper during the next growing season, so bud caps do not need removal. Reapply bud caps yearly until the tree is at least four feet tall and out of the reach of deer.
Repellants can minimize deer browsing on white pine seedlings. Nuisance Wildlife Repellent Handbook
Consider fencing seedlings when the threat of deer is excellent. The size of your planting, the number of deer in the area, and the cost of supplies should be considered with this option.
Pruning Basics
Careful pruning of white pine limbs helps reduce damage from blister rust and white pine weevil. It also helps trees grow straighter and produce higher-quality wood products. To maintain adequate growth, leave two-thirds of the tree's height with branches. It is best to start pruning trees when they are small.
When pruning:
- Use pruning shears or pruning saws (chain saws are not recommended).
- Do not cut the limbs off flush with the trunk or leave branch stubs (see diagram). When pruning, leave the branch collar. Cut from point A to point B.
- Prune during the tree's dormant season (fall, winter).
- Never remove more than half the crown.
- Remove the bottommost branches.
White Pine Diseases
Controlling White Pine Blister Rust
Blister rust is a fungal disease that creates cankers by killing areas of bark and outer wood. Most infections occur within 9 feet of the ground. The needles of branches with cankers die and turn orange.
The white pine blister rust pathogen must first infect plants in the Ribes genus (primarily currant and gooseberry) before it can infect white pine. Killing or removing ribe plants within 200 feet of white pine can reduce white pine blister rust infections.
To prevent branches from becoming infected, begin pruning lower branches when white pine trees are 5 to 7 years old. Remove no more than one-third of the crown at a time. Continue pruning over time until the lower 9 feet of the tree is free of branches. See the Pruning Basics section for proper pruning instructions.
Remove branches that become infected with white pine blister rust. Trees with blister rust cankers on the main stem or a branch within 4 inches of the main stem cannot be saved. Blister rust does not transmit from tree to tree, so infected trees can remain standing.
It is unnecessary to paint over the branch stubs of the pruned limbs, clean up or remove pruned branches, or sanitize pruning tools between uses.
Controlling White Pine Weevils
White pine weevils are native insects that kill terminal shoots of white pines, particularly open-grown trees under 20 feet tall. Attacked trees grow slower in height and develop a poor form for lumber. White pines under four feet tall can be killed. Planting at higher densities or under partial shade will drastically reduce white pine weevil infestations.
Trees with killed terminal leaders can be correctively pruned so that only one side branch becomes the terminal leader. This will help trees recover height growth and form. Collect and destroy clipped terminals.