Pinus greggii

Taxonomy

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

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.

The needles are (7-)9-13(-15) cm x 1-1.2mm bright lustrous green, in fascicles of three, and with a short basal sheath.

The pollen cones are crowded near the basal end of a new shoot. They are subtended by broad, scarious bracts, spreading, ovoid-oblong to cylindrical, 15–20 × 5–6 mm, yellowish, turning yellowish brown.

The seed cones are (6-)8–13(-15) cm long 3.5–5 cm wide when closed, opening to (4-)5–7 cm wide, 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.

Pinus greggii is closely related to, and has been crossed successfully with, Pinus patula. The main morphological difference with the latter species is found in the needles, with those of P. patula are longer and drooping; the cones of P. patula are also smaller, under 10 cm long.

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 has more resistance to frost than most other Mexican pines, particularly in the range of nominate var. greggii, where temperatures down to -15°C have been recorded during norte events in Galeana, Nuevo León (1700 m), and lower than that in the mountains where P. greggii occurs; 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

Literature

• 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

References

1. in Candolle, Prodr. 16 (2): 396 (1868); distribution: Mexico, Sierra Madre Oriental, cited in Farjon 2001, p. 179
2. "''Pinus greggii'' Engelm. ex Parl.".
3. (2009). "Pinus L.". Journal of the International Conifer Preservation Society.
4. distr: Mexico, Coahuila, Nuevo León (given with no further ref. in Farjon 2001, p. 179)
5. (1998). "A new variety of ''Pinus greggii'' (Pinaceae) in Mexico". Sida.
6. Farjon 1984, p. 83 says: small tree 15m; Farjon&Styles 1997, p. 193 says small to medium, height to 20–25 m
7. Farjon 1984, p. 83
8. Farjon&Styles 1997, p. 193
9. spreading or curved downward, not pendulous, forming a rounded, dense or more open crown. The young twigs are bluish-green with a glaucous wax bloom at first, becoming reddish brown to grey-brown later.Farjon 1984, p. 83; Farjon&Styles 1997, p. 193
10. Farjon&Styles 1997, p. 193; Farjon 1984, p. 83 says: 8–15 cm long, yellowish-green and thin
11. Farjon&Styles 1997, p. 193; Farjon 1984, p. 83 says: 8–15 cm long
12. In its native environment ''Pinus greggii'' begins flower and cone production at approximately 4 to 5 years of age. The cones ripen in December and January, approximately 21 months after pollination.Dvorak 2003, p. 616
13. Dvorak 2003, p. 615
14. Farjon&Styles 1997, p. 193; Farjon 1984, p. 83 says: between 1500 and 2700 m
15. (1985). "Some plants collected in Mexico". The Garden.
16. (1972). "Conifers in the British Isles". Forestry Commission.
17. One was also planted at [[Fota Island#Fota Gardens
18. den Ouden & Boom 1965 do not have information on ''Pinus greggii''