Picea chihuahuana Martínez

Species Nomenclature

Picea chihuahuana, commonly known as the Chihuahua spruce, is a medium-sized evergreen tree that reaches 25 to 35 meters in height, with a trunk diameter of up to 1 meter.

Native Range

It is native to northwestern Mexico, where it grows in 25 small populations in the Sierra Madre Occidental mountains of Chihuahua and Durango.

Altitude Range

It occurs at moderate altitudes ranging from 2300 to 3200 meters, growing along streamsides in mountain valleys.

Habitat Soil Moisture

In these locations, soil moisture levels are higher than would be expected given the area's otherwise low rainfall.

Bark Characteristics

Its bark is thin and scaly, flaking off in small circular plates 5 to 10 centimeters across.

Crown and Branch Structure

It has a conical crown with widely spaced branches and drooping branchlets.

Shoot Characteristics

Its shoots are stout, pale buff-brown, glabrous, and marked with prominent pulvini.

Leaf Morphology

The leaves are needle-like, 17 to 23 millimeters long, stout, and rhombic in cross-section. They are bright glaucous blue-green with conspicuous lines of stomata, and have a sharply pointed tip.

Cone Shape

The cones are pendulous and broadly cylindrical.

Cone Size

They are 7 to 12 centimeters long and 3 centimeters wide when closed, and open to 4 to 5 centimeters wide.

Cone Scale Features

They have stiff, bluntly rounded scales that are 1.5 to 2 centimeters wide.

Cone Color and Maturation

The cones are green when young, and mature to pale brown 6 to 8 months after pollination.

Seed Characteristics

The seeds are black, 4 millimeters long, with a pale brown wing 10 to 13 millimeters long.

Taxonomic Discovery

Chihuahua spruce was first discovered in 1942 by Mexican botanist Maximino Martínez.

Conservation Status

It is classified as endangered, with only 25 small populations, none of which contain more than a few hundred trees.

Related Species

It is related to Martinez's spruce (P. martinezii), which grows in northeast Mexico. It differs from P. martinezii by having shorter blue-green leaves, and smaller, narrower cones with smaller scales.

Phylogenetic Relationships

No other closely related spruces grow in North America; its next closest relatives are native to eastern Asia.

Ornamental Use

It is a very attractive tree, and is beginning to be planted as an ornamental in botanical gardens.

Heat Tolerance

It is particularly valued for planting in warm areas, as it is one of the most heat-tolerant of all spruces. It tolerates summer heat better than blue spruce (P. pungens), a species it resembles in foliage.