Pinus discolor Bailey and Hawksworth 1979

Common Names

Border piñon (1).

Taxonomic notes

Subsection Cembroides. Syn: P. cembroides subsp. cembroides var. bicolor Little 1968; P. culminicola var. discolor (Bailey and Hawksworth) Silba 1985 (3).

The validity of this taxon is greatly disputed. At one extreme, Kral (4) summarily dismisses its existence altogether, and Farjon and Styles (3) regard it, combined with P. johannis Robert-Passini, as merely a variety of P. cembroides (var. bicolor Little) while at the other extreme, Perry (2) and Price et al. (5) regard it as a valid species distinct in its own right. An intermediate view is taken by Passini (6), 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; the combination Pinus johannis var. bicolor has however yet to be formally 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 (7) 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 (8) in a very detailed study), but is not widely followed.

Description

As Pinus johannis except:
  1. Often a small tree (to 9-15 m), while P. johannis is usually a shrub and never more than c. 5 m tall.
  2. Cones slightly smaller, not over 3.5 cm long (to 4.5 cm in P. johannis), but with considerable overlap.
  3. Cone scales smoother, orange-pigmented and slightly glossy (finely wrinkled and more or less matt mid-brown in P. johannis).
  4. 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 (9), but the taxonomic significance of this research has been questioned (3).

Range

S Arizona & New Mexico. Notably, Kitt Pk. and the Santa Catalina Mtns. (1). Mexico: Sonora, Chihuahua and Durango at 1500-2400 m (2).

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

Citations

(1) Lanner 1981.
(2) Perry 1991.
(3) Farjon & Styles 1997.
(4) Kral in Flora North America
(5) Price et al. 1998.
(6) Passini 1994.
(7) Silba 1985.
(8) Malusa 1992.
(9) Zavarin, E. & Snajberk, K. 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, Feb-1999.

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This page is from the Gymnosperm Database
URL: http://www.geocities.com/~earlecj/pi/pin/di.htm
Edited by Christopher J. Earle
E-mail:earlecj@earthlink.com
Last modified on 27-Dec-1999

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