Pinus strobiformis Seeds | Southwestern White Pine
LATIN NAME: Pinus strobiformis
COMMON NAME: Southwestern White Pine, Mexican White Pine
Plant Profile
Southwestern white pine is a five-needle pine of the Mexican border mountains, and it is a tree of the sky islands, where each range holds its own population. It reaches 25 to 30 metres, with a straight trunk and a crown that is narrow and conical when young and becomes irregular and open with age. The needles are long, slender, blue-green and slightly drooping, in bundles of five, and the cones are large — 15 to 25 cm — resinous, cylindrical and often curved, hanging from the ends of the upper branches. The seed is large and winged, and it is eaten by birds and squirrels. It grows in the mountains of Arizona, New Mexico and west Texas, and south through the Sierra Madre of Chihuahua, Sonora and Durango, usually between 2000 and 3000 metres, in mixed forest with Douglas fir and limber pine.
Science & Biotechnology
The species belongs to the white pine group, subsection Strobus, and it is closely related to P. flexilis and to the Mexican P. ayacahuite, with which it forms a complex of intergrading populations along the border. That relationship is not merely academic: the white pines share a susceptibility to white pine blister rust, Cronartium ribicola, a fungus introduced from Asia that has devastated five-needle pines across North America. Southwestern white pine shows some genetic resistance, and it is one of the species screened in breeding programmes that aim to produce resistant stock for reforestation. The tree is also a key component of sky-island forests, which are isolated by desert and therefore act as natural laboratories for studying how species shift with climate. Its large seed makes it important to wildlife.
Uses & Benefits
It is a timber tree in Mexico and in parts of its US range, where the wood is used for construction, boxes and pulp, and it is planted as an ornamental in large gardens and parks in the dry Southwest, where its blue-green needles and tolerance of drought make it a good substitute for less adapted pines. The seed is eaten by squirrels, by the Mexican jay and by other birds, and it is one of the species that supports the wildlife of the sky islands. In a garden it needs space and sun, and it is not a tree for a small plot. The species is also used in reforestation and in restoration planting on burned sites, where its relatively fast growth and its drought tolerance give it an advantage over slower conifers.
Growing from Seed
Cold, moist stratification for six to eight weeks helps, though this species germinates more readily than many white pines. Sow in autumn and leave the pot outside, or stratify and sow in spring at 18 to 20 °C. The seedlings are susceptible to damping-off, so use a well-drained mix and do not overwater. Grow them in full sun with good air movement, and pot on before the roots circle. Plant out at two or three years in autumn, on a site with deep, well-drained soil and full sun, and protect the young tree from deer and from strong wind. Water through the first three summers. The tree is hardy to about minus 25 and tolerates dry air and alkaline soil better than most white pines.
Our Take
A handsome five-needle pine for a dry mountain garden, and a species whose future depends on the blister-rust resistance work now under way.
Related Reading
Gardeners who grow Southwestern White Pine often pair it with these related subjects: