Where to plant and grow white pines
White pine can and does grow in all parts of Minnesota. White pine
blister rust hazard zones (see map) indicate the general level of hazard
over broad geographic areas but should not be used to determine
hazard on a specific site. White pine can be grown successfully in all
hazard zones, but as hazard increases, it becomes more important to carefully
select planting sites (soils, topography, shade) and to implement pest
management strategies (see Tending Your White Pines section).
White pine occurs naturally on a wide range of soil types and textures.
Good growth occurs on most soil textures and soil drainage classes. It
is more tolerant of wetter conditions than red or jack pine but is less
tolerant of droughty conditions. Best growth will occur on sites with:
medium to fine soil texture, medium to high soil fertility, somewhat poor
to well drained soil, constant moisture supply and rooting zone greater
than 18 inches deep. Avoid the extremes of heavy, continually wet soils
and coarse, drought-prone soils when selecting a planting site.
Plant white pines on steep slopes, hill tops and shoulders of hills.
Avoid V-shaped valleys,
potholes, bases of slopes and small openings in the forest canopy anywhere
in Minnesota. A small opening is one where the spaces between the crowns
are 1/4 to one times the height of the surrounding trees. These features
favor the collection of cool, moist air and favor infection by the white
pine blister rust fungus in both northern and southern Minnesota.
White pine grows better and has better form if growing under the shade
of other trees. Unlike red pine or jack pine, white pine can easily tolerate
growing under an overstory. Planting under an overstory has two benefits,
namely, reduced risk of white pine blister rust infection and reduced risk
of white pine weevil attack.
Aspen, birch, oak and other hardwoods are good choices for the overstory.
Tree species that are intermediate or shade intolerant, such as, aspen
and birch, have smaller, thinner crowns that allow light to penetrate to
the understory. Shade tolerant species, such as, sugar maple and basswood,
have large, dense crowns that intercept lots of light and are likely to
significantly reduce the growth of the understory white pines.
High shade (from overstory trees that are significantly taller than
the white pines) is preferred to shade from brush and shorter trees that
are similar in height to the white pines. High shade is beneficial; less
incidence of blister rust and better growth.
Look for and choose the sites: where aspen (or birch) is mature and
the stand is breaking up, where a hardwood stand just underwent thinning
or where a stand was partially harvested. The overstory should be vigorous
enough to survive an additional twenty to thirty years. Heavy or continuous
shade can be detrimental to white pine growth, so, as a goal, maintain
approximately 40 to 60 percent shade. You can tell if you're on the right
track with the correct amount of shading if the white pine seedlings grow
about 1 to 1 ½ feet in height per year after being established for
six to eight years.
Shade or no shade. Planting white pine seedlings in the open
(like in an old field) is more acceptable in Hazard Zones 1 and 2 because
the climate is less favorable to white pine blister rust infection. In
Zone 2, blister rust can be a problem so avoid open field planting in V-shaped
valleys, potholes and the bases of slopes.