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Tree to 40 m. Bark grey, thin and scaly. Crown conical and irregular. Branchlets yellow, glabrous, pulvini small; vegetative buds not resinous. Leaves spreading forwards, dark green, glossy, flattened in cross-section, though – uniquely in Picea – they are flattened from side to side rather than dorsiventrally, (1.6–)2.3–2.7 × 0.1–0.2 cm, apex acute and sharp. Male strobili unrecorded. Cones terminal, oblong-cylindrical, 8.5–16 × (4–)5.5–6.2 cm, green initially, reddish brown when mature. Seed scales obovate, (1.9–)2.6–3.2 × (1.8–)2.1– 2.5 cm, denticulate, apex reflexed. Seeds brown, fusiform, 0.5–0.8 cm long, wings 1.6–2.3 cm long. Rushforth 1986a, Patterson 1988. Distribution MEXICO: southwest Nuevo León (El Butano, Cañada La Tinaja). Habitat Temperate montane forest between 2150 and 2200 m asl. This species is known from only two locations in Nuevo León, where it grows in deep pockets of soil trapped between limestone blocks with a constant water supply. USDA Hardiness Zone 7–8. Conservation status Critically Endangered. Illustration NT563, NT575. Taxonomic note Picea martinezii was first described by Patterson (1988), who noted several characters that could be used to distinguish it from P. chihuahuana, but Farjon (2001) placed it in synonymy with P. chihuahuana. An analysis of the morphology and biochemistry of the Mexican spruces suggests that P. martinezii is a distinct taxon (Taylor et al. 1994), and cultivated material does appear to differ markedly from that of P. chihuahuana. The main features distinguishing the two are: leaf colour (glossy green in P. martinezii vs. blue-green in P. chihuahuana), leaf length (usually 2.3–2.8 cm vs. 1.2–2.3 cm), cone size (8.5–16 × 5.5–6 cm vs. 7–12 × 4–5 cm), seed scale density (12–16 scales per 10 cm cone length vs. 25–30 scales per 10 cm) and seed scale size (2.6–3.2 × 2.1–2.5 cm vs.1.8–2.3 × 1.4–2 cm). Another observed difference is a distinction in the arrangement of the leaves; in P. chihuahuana they are held more or less perpendicular to the stems (patent) and thus bristle outwards, while in P. martinezii they can be somewhat appressed on the upper surface of the shoot but patent on the lower surface.
Despite its rarity in the wild Picea martinezii is well established, if scarce, in cultivation. It certainly deserves to be grown, as a particularly attractive spruce, but this rarity makes it essential that material is carefully conserved, with details of its provenance maintained. It is thriving at Kew (where it is labelled as P. chihuahuana), forming densely clad, vigorous young trees. A group of three grown from Priest 108, collected at Ejido do la Encantada, Zaragoza, Nuevo León in 1984, are particularly attractive; they were approximately 5 m tall when observed in 2005 but have since grown considerably, and produce a heavy crop of cones each year. A tree from a collection made by Keith Rushforth (KR 551A) at the same site in 1984 is also doing well at Kew. At Arboretum Wespelaar it is flourishing from a collection made by Rob Nicholson and team from the Arnold Arboretum in 1997 at El Butano, Nuevo León, and shows the same dark green leaves as the Kew trees – a character that immediately sets it apart from the glaucous P. chihuahuana, although the needles are equally sharp. A 2.5 m tree growing at the JC Raulston Arboretum originating from Yucca Do Nursery, Hempstead, Texas is thriving, forming a shapely, dense specimen that withstood the 2006–2007 drought well (M. Weathington, pers. comm. 2007).