Pinus strobiformis aka Southwestern White Pine

Pinus strobiformis is an evergreen tree in the pine family. Its common names include southwestern white pine and Mexican white pine. It also goes by the name Chihuahua white pine. Most of its native range lies within Mexico. Kew lists eastern Sonora south to Durango and Jalisco. Oregon State gives a wider range that includes southwestern US mountains. That account includes Arizona, New Mexico, western Texas, and southwestern Colorado. The two sources thus differ on its northern limits.

Oregon State reports trees reaching 90 feet [27 metres] tall. The supplied sources give no separate range for garden size. Young trees have a straight trunk and a cone-shaped crown. With age, the crown grows broad and may flatten on top. Long branches may stretch sideways, hang down, or turn upward. This gives older trees an open and uneven outline. Young bark is smooth and has a gray-brown color. As it ages, furrows divide the bark into rounded, scaly ridges. The twigs start green and turn gray-brown with age.

The soft needles grow in bundles of five. They are thin and blue-green, with fine teeth near their tips. White stomatal lines mark only the inner faces of each needle. The sources give needle lengths from about two to four inches. The sheath around each needle bundle falls off soon. Buds have an egg-like or cone-like shape. These leaf and cone traits help separate this pine from limber pine. Oregon State also reports that the two species can form hybrids.

Each tree bears both male and female cones. Pale yellow male cones form clusters near the branch tips. Female cones range from light green to reddish near branch ends. The woody seed cones turn yellow-brown and ripen in late summer. The sources describe cones about five to ten inches long. Their thick scales bend back and have narrow tips. Mature cones open to release seeds that have almost no wings. Oregon State gives seed lengths of ten to twelve millimetres.

Grow this tree in full sun. Oregon State reports best growth on cool, moist sites with deep soil. Chicago Botanic Garden also lists it for dry soil. Its upright form suits screens and hedges. Chicago lists USDA zones 5–7, while Oregon State reports hardiness to zone 4.