Pinus discolor

Bailey and Hawksworth 1979

Common names

Border piñon (Lanner 1981).

Taxonomic notes

Subsection Cembroides. Syn: P. cembroides subsp. cembroides var. bicolor Little 1968; P. culminicola var. discolor (Bailey and Hawksworth) Silba 1985 (Farjon & Styles 1997).

The validity of this taxon is greatly disputed. At one extreme, Kral (1993) summarily dismisses its existence altogether, and Farjon & Styles (1997) regard it, combined with P. johannis Robert-Passini, as merely a variety of P. cembroides (var. bicolor Little) while at the other extreme, Perry (1991) and Price et al. (1998) regard it as a valid species distinct in its own right. An intermediate view is taken by Passini (1994), who treats P. discolor as a synonym of P. johannis. It is clearly very close to that species but does differ slightly, and might best be treated as a variety of it, but the combination Pinus johannis var. bicolor has not yet been published.

There have been no reports of any natural hybridisation with P. cembroides, despite frequent intermingled occurrence, which strongly supports specific distinction from P. cembroides. Pending further research, it is retained as a species here.

The view of Silba (1985) that it and P. johannis are varieties of P. culminicola has some merit in showing that they are more closely related to P. culminicola than to P. cembroides (a fact subsequently demonstrated by Malusa (1992)), but is not widely followed.

Description

As Pinus johannis except:

• Often a small tree (to 9-15 m), while P. johannis is usually a shrub and never more than c. 5 m tall.
• Cones slightly smaller, not over 3.5 cm long (to 4.5 cm in P. johannis), but with considerable overlap.
• Cone scales smoother, orange-pigmented and slightly glossy (finely wrinkled and more or less matt mid-brown in P. johannis).
• The seeds average slightly smaller, to 12 mm (to 14 mm in P. johannis), again with considerable overlap.

Some of these differences are based on small sample sizes, and may prove inconclusive with further research. Differences in the composition of the turpentine have also been reported (Zavarin & Snajberk 1986), but the validity of this research has been questioned (Farjon & Styles 1997).

Range

S Arizona & New Mexico. Notably, Kitt Pk. and the Santa Catalina Mtns. (Lanner 1981). Mexico: Sonora, Chihuahua and Durango at 1500-2400 m (Perry 1991).

Big tree

Oldest

Dendrochronology

Ethnobotany

Potentially a valuable slow-growing ornamental species for small gardens in drought-prone areas, but it is scarcely in cultivation yet. USDA hardiness zone 8.

Observations

Remarks

This species is one of the principal hosts for the dwarf mistletoes Arceuthobium pendens (Hawksworth and Wiens 1996).

Citations

Zavarin, E. and K. Snajberk. 1986. Monoterpenoid differentiation in relation to the morphology of Pinus discolor and Pinus johannis. Biochem. Syst. Ecol. 14: 1-11.

Much of this page was prepared by M.P. Frankis, 1999.02.

See also