Feature Tree - June 2003
Southwestern White Pine

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Common Name: Southwestern White Pine

Scientific Name: Pinus strobiformus

Family:  Pinaceae

This Tree in Colorado: Southwestern White Pine is native to Colorado. This tree is found in the southwestern part of the state in its native habitat on ridges, slopes and canyons and grows in mixed stands up to timberline and is found occasionally in the montane riparian zones. It is also planted in urban landscapes. It grows well in a variety of soils, preferring loamy soils and disliking poorly drained soils.

Growth Rate, Form and Size: Southwestern White Pine has a moderate rate of growth. After they are established in the landscape the growth rate will be around 12” per year. Young trees are dense, symmetrical and pyramidal in form. In most urban settings, it will reach 35 to 50 feet but can grow to 90 feet in its native habitat. It has an open irregular crown with long, horizontal branches with a mature spread of 20 to 30 feet.

Landscape Value: The horizontal to somewhat drooping branch structure with soft bluish-green needles provide an attractive landscape element year-round. Based on its mature size, this tree will need plenty of room to grow. It is not shade tolerant so it should be placed away from other large trees. Multiple specimens may be planted to create a windbreak. Because of its mature height, do not plant this tree under overhead power lines.

Hardiness Zones:                                        

Leaves/Needles: The needles of the southwestern white pine are in fascicles (bundles) of five. They are soft, bluish-green and 2.5 to 4 inches long. They are susceptible to salt spray, so care should be taken in planting them too close to roads.

Cones: The oval cones are 3 to 10 inches long with thick scales that are distinguished by a curled lip. They are light brown in color and are dehiscent (fall off) when mature. The seeds are wingless and are palatable to small mammals and birds.

Bark: The bark is ashy gray when young becoming blackish gray, rough and furrowed as the tree matures.

Insects and Diseases: The southwestern white pine has been shown to be susceptible to white pine blister rust. It is fire sensitive when young. Older trees with thicker bark are more fire resistant. The thin bark and horizontal branches increase its susceptibility to fire.

Information Sources:  Pavek, Diane S., Pinus strobiformus, 1993 as found in www.1upinfo.com

As with all Trees of the Month, considerable more information can be obtained by searching the web under the name, Southwestern White Pine.