Forest Insect and Disease Newsletter: White Pines

How to plant white pines

What to plant
A variety of planting materials are available.

  1. Seedlings grown from seed collected in Minnesota may be better adapted to local conditions than seedlings from seed collected in other states. Verify the seed source with your grower.
  2. Container stock, bare-root seedlings, bareroot transplants or even larger trees can be selected. Being larger, bareroot transplants, may survive better when planted in the shade of an overstory canopy.
  3. Currently, there are no sources of planting stock proven to be resistant to white pine blister rust. Seedlings advertised as "resistant" may cost more and have no proven benefit.

Site preparation
Although white pine seedlings can do well in partial shade of overstory trees, they can be choked out by the shade of competing grasses, weeds and shrubs. These plants can be controlled or killed prior to planting by hand cutting, herbicides or scarification of the patches where the seedlings will be planted. A recent innovation is to use a "weed control" mat for each seedling. It inhibits weed and grass growth immediately around the planted seedling. The mat may be made out of a variety of materials including mulch, cardboard, jute or polypropylene. It should be about three feet in diameter. Solid materials need to be weighed down with soil or rocks and a few holes poked through them to allow water to soak through.

Ribes reduction
Additional site preparation and tending work may be done to improve seedling and sapling survival. Since blister rust needs both the white pine and the Ribes to complete its life cycle, getting rid of the Ribes breaks the life cycle and therefore prevents blister rust infections. To prevent or minimize white pine blister rust infections, Ribes ( currants and gooseberries) could be eliminated in and around high value plantings. Ribes are most easily identified in the early spring. 1. The effectiveness of Ribes eradication varies by location. It's most effective in Hazard Zone 1 and least effective in Zone 4. (See map in Site Selection.) If time and energy permits, eradicate Ribes in a buffer around the planting area, too. In Hazard Zone 1, eradicate Ribes in a 50 foot buffer, in Zone 2 = 70 feet, Zone 3 = 600 feet, and Zone 4 = 900 feet. 2. Pull up or treat all the Ribes species in the planting area. This should be done prior to planting and again two or three more times at three year intervals in order to get rid of the plants germinating from seed stored in the soil. 3. Don't plant gooseberries and currants near high value plantings of white pine.

When to plant
Spring is usually the best time to plant white pine. Soil moisture is usually good and cooler conditions help prevent drying of the young seedlings. In southern Minnesota, planting season is from early April to early May, whereas, in northern Minnesota, the season is late April to mid-May.

Handling and storage of seedlings
Due to root desiccation, white pine seedlings may die before they even get their roots in the ground. Care must be taken so that young, bareroot seedlings are kept cool and moist right up until the time they are planted. When you receive your tree seedlings, check to make sure the roots are moist. If they are especially dry and crackly, return them to the nursery. If they are somewhat dry, wet them down and try to plant them as quickly as possible. If you need to store them for a few days before planting, keep them inside the package they were shipped in, find a cool, well shaded spot and allow for a limited amount of air circulation around the package. The sooner you plant them, the better their chances of survival. During the planting process, make sure the tree roots are kept moist and are not expose to long periods of sunlight or drying winds. Even a few minutes of exposure to a light breeze on a sunny day will kill the roots ( and the seedling).

Planting methods
White pine seedlings can easily be planted using a shovel, hoedad or planting bar. Always plant in mineral soil, not in the duff or litter layer. Tree planting machines can be used for open field plantings, especially in southern Minnesota, where the risk of blister rust and weevil are low. 1. Make sure the hole is deep and wide enough to allow the roots to fully extend down and out to the side. Roots should assume a natural position and not be twisted, compacted or stick out of the hole. 2. Plant the seedling at the same depth it grew in the nursery. If planted too deep, roots will become curled and the seedling is more likely to be killed by insects and diseases. If planted too shallow, some roots will be exposed to the air and they will die. 3. Refill the hole with soil and pack the soil firmly around the root system. Avoid creating air pockets around the roots, creating a mound or depression near the stem or allowing large amounts of organic matter to be incorporated into the planting hole.