Jeffrey pine (Pinus jeffreyi) is a North American pine related to Ponderosa Pine. It occurs from southwest Oregon south through much of California (mainly in the Sierra Nevada), to northern Baja California in Mexico. It is a high altitude species; in the north of its range, it grows at 1000-2000 m altitude, and at 1800-3000 m in the south of its range.

It is a large tree, reaching 25-40 m tall, rarely up to 55 m tall, though smaller when growing at or near tree-line. The leaves are needle-like, in bundles of three, stout, glaucous gray-green, 12-23 cm long. The cones are 12-24 cm long, dark purple when immature, ripening pale brown, with thinly woody scales bearing a short reflexed spine. The seeds are 10-12 mm long, with a large (15-25 mm) wing.

It may be distinguished from Ponderosa Pine by the needles, which are glaucous, less bright green than those of Ponderosa Pine, and the stouter, heavier cones with larger seeds. Jeffrey Pine is also very distinct from Ponderosa Pine in its resin scent, like lemon or vanilla, compared to the turpentine scent of Ponderosa Pine. This may be tested by breaking a small shoot or some needles, or by sampling the scent of the resin in between the plates of the bark. This difference in scent is related to the very unusual composition of the resin, with the volatile component made up almost entirely of pure n-heptane.

Jeffrey Pine is tolerant of serpentine soils, and is often dominant in these conditions, even on dry sites at fairly low altitude. On other soils, it only becomes dominant at higher altitudes where the usually faster-growing Ponderosa Pine does not thrive.

Uses

Jeffrey Pine wood is similar to Ponderosa Pine wood, and is used for the same purposes. The exceptional purity of n-heptane distilled from Jeffrey Pine resin led to n-heptane being selected as the zero point on the octane rating scale of petrol.

As n-heptane is explosive when ignited, Jeffrey Pine resin cannot be used to make turpentine. Before Jeffrey Pine was distinguished from Ponderosa Pine as a distinct species in 1853, resin distillers operating in its range suffered a number of 'inexplicable' explosions during distillation, now known to have been caused by the unwitting use of Jeffrey Pine resin.