Pinus nelsonii Shaw

Pinus nelsonii is a thoroughly weird pine, unique in numerous features. Although discovered in 1904, it may not have been introduced until recently, as the specimen at Kew referred to by Bean (1976b) was later recognised as P. orizabensis (see p. 612). The cones of P. nelsonii are the strangest in the genus, with the conelet, unlike in any other pine, not ceasing growth in the first winter; the umbo is therefore large and grades into the apophysis. The cone is also unusual in that the peduncle occasionally bears needle fascicles, again not seen in any other pine. The needles are unique in remaining connate throughout their lifetime (‘zippered’ together by the marginal teeth) (Bailey & Hawksworth 1988). Pinus nelsonii forms a short, bushy tree, with a crown shaped similarly to that of young P. pinea. The needles are bright green, and young plants bear green (not glaucous) juvenile leaves for up to ten years. It has proved to be the most distinct pine of all genetically, not closely related to any other, and now placed in its own section, Nelsonia (Businský 2008). In the wild it grows in arid situations, often with P. cembroides. Gatherings have been made by a few collectors, including Frankis 183 from Nuevo León in 1991, a tree from which in the Rock Garden at Edinburgh was about 2 m tall and coning in 2006, probably the first cones of this species ever produced in the United Kingdom. It has also been collected by Carl Schoenfeld and John Fairey, from whose material a tree has grown at Berkeley since 1997. Wider cultivation should be attempted, though more for its interest as a botanical curiosity than for its decorative qualities.

Bean’s Trees and Shrubs

A small tree with pale glaucous or whitish shoots. Leaves in threes, usually adhering and apparently single in wild plants, slender, up to 2{1/2} in. long (occasionally longer), three-sided, light green on the outer side; sheaths persistent, about {1/4} in. long, not reduced to a rosette. Cones cylindrical or oblong-ovoid, up to 5 in. long, pendulous from the downward curving of the stout peduncle, which is 1 to 2 in. long; scales relatively few, the exposed part rhomboidal, the transverse diameter much the larger, with wide, prominent umbos; seeds large, wingless, edible (Gard. Chron., Vol. 36 (1904), p. 122, fig. 49).Native of N.E. Mexico. A tree at Kew, planted in 1910, is considered to belong to this species. It measures 32 × 2{1/4} ft (1969).

From the Supplement (Vol. V)

The plant at Kew, mentioned on page 219, is of doubtful identity and may be P. cembroides. It measures 36 × 31⁄4 ft (1984).