Pinus greggii

The species was described by George Engelmann in 1868. Two varieties are accepted, sometimes treated at the higher rank of subspecies. • Pinus greggii Engelm. ex Parl. var. greggii • Pinus greggii Engelm. ex Parl. var. australis Donahue & Lopez, occurring in east-central Mexico in San Luis Potosi, Querétaro, Hidalgo, and Puebla The species is named after Josiah Gregg (1806–1850), a merchant, explorer, naturalist, and author of the American Southwest and Northern Mexico. ==Description==

, Coahuila , San Luis Potosí Pinus greggiii is a small to medium-sized tree, reaching a height of 15–25 m. The bark remains smooth for a long time in this species, and only old trees have rough bark at the base of the trunk, where it becomes thick, with deep, longitudinal fissures and rough, elongated plates. On the upper part of the trunk and branches, it remains smooth to scaly, and greyish-brown. The crown is loose and open. The branches are long and slender, The winter buds are narrow and sharp pointed, without resin and with loose scales, usually light-brown. in fascicles of three, and with a short basal sheath. light buff-brown when ripe, long, often slightly curved, and remain closed for many years until opened by the heat of forest fires, enabling seed release just after the fire. They have an irregular conical shape. They are found singly or in clusters of up to 5–10 on the branches. The apophysis has a weak transverse keel and a blunt umbo. ==Distribution==

Pinus greggii is found in Mexico in the Sierra Madre Oriental, only in a limited area in the states of Coahuila, Nuevo León and Hidalgo. It occurs farther north than its close relative, Pinus patula, though the range of var. australis overlaps slightly. Natural hybrids exist and that artificial hybrids have been successfully made. Dvorak states that Pinus greggii occurs in two distinct geographic regions in Mexico: a northern population in the States of Coahuila and Nuevo León (24° to 25° N latitude), and a southern population in the States of Puebla, San Luis Potosí, Hidalgo, Querétaro, and Veracruz (20° to 21° N). There is a gap of 360 km between these two populations. There are differences in needle and cone morphology and seed size between the two populations. There are also differences in ecology and size of trees. ==Ecology==

In its natural habitat Pinus greggiii grows in the cool highlands, at altitudes between 1300–2600 m; in the northern part of its distribution at 2300–2700m. Annual precipitation is 600–800 mm in much of its range, except on the east escarpment of the mountain ranges along the Hidalgo-Veracruz borderline, where it is 1000–1600 mm. In the north it is more often found on slightly alkaline soils (pH 7–8); in the south on acid soils (pH 4–5). it is also hardy in cultivation in England, including surviving the severe 1946–47 and 1962–1963 winters at Bedgebury Pinetum. Usually the climate is rather humid in these mountains of northeastern Mexico. It is nowhere abundant in its scattered range, and always occurred mixed with e.g. Quercus, Platanus, Liquidambar, Fraxinus, and other pines, like P. montezumae, Pinus patula, P. stormiae, P. stylesii, and P. teocote; with P. cembroides and Juniperus flaccida on dry sites; and at higher and more mesic locations with Abies vejarii, Pseudotsuga menziesii or Cupressus arizonica. ==Cultivation and introductions==

The first recorded introduction of Pinus greggii was to Britain in about 1905 from the northern population; two specimens were at first grown under glass at Kew but then moved to outdoor planting at Bedgebury in 1926; one of these died in 1965, the other survived until the mid 1970s, by which time other introductions had been made. ==References==

• Dvorak, W. S. Pinus greggii. In: Vozzo, J.A. Tropical Tree Seed Manual. United States Department of Agriculture; Forest Service. 2003. p. 615–617. online available as pdf • Farjon, Aljos. Pines; drawings and descriptions of the genus Pinus. Publ. Brill / Backhuys, Leiden 1984 • Farjon, Aljos & Brian T. Styles. Pinus (Pinaceae). Monograph 75 of Flora Neotropica. New York Botanical Garden, New York 1997 • Farjon, Aljos. World checklist and bibliography of Conifers. 2nd ed. Royal Botanic Gardens, Kew 2001 • den Ouden, P. & Dr. B.K. Boom. Manual of Cultivated Conifers, ed. Martinus Nijhoff, The Hague 1965 • Shaw, George Russell. The genus Pinus. Cambridge 1914. online in gutenberg.org. With beautiful drawing. • van Wyk, G. Pinus greggii. In: Pines of Silvicultural Importance. Compiled from the Forestry Compendium, CAB International. Edition: illustrated. Published by CABI, 2002. , , p. 144f. Online available at Google Books ==External links==