Picea martinezii T.F. Patt.

When Patterson described Picea martinezii in 1988 (Patterson 1988) it had already been in cultivation for at least three years, from Priest 108 and Rushforth 551A, both gathered at Ejido do la Encantada, Zaragoza, Nuevo León in 1984 when it was thought to represent a remote population of Chihuahua Spruce, P. chihuahuana (Grimshaw & Bayton 2009; Rushforth 1987). Indeed, Farjon (1990; 2001) treated P. martinezii as synonymous with Chihuahua Spruce, but it has long been considered amply distinct by those who have seen it in the wild, and by most others following the analysis of Taylor, Patterson & Harrod (1994) and it is now treated such in most major works (e.g. Debreczy & Rácz 2011; Farjon 2017).

Although a rare, local endemic in the wild, Picea martinezii is relatively well established in cultivation, albeit from only a handful of gatherings. Still, it is proving itself remarkably hardy and adaptable: trees are thriving in such diverse locations as Kew (increasingly hot and dry), Benmore Botanic Garden (Argyll, UK, characterised by a cool and extremely wet climate), the JC Raulston Arboretum (North Carolina, USA, with warm, humid summers, the Botanical Garden of Geneva, Switzerland, and in private collections in Hungary, the latter within a distinctly continental climate zone (pers. obs.).

The group of three from Priest 108 at Kew, mentioned in New Trees (‘approximately 5 m tall when observed in 2005 but have since grown considerably, and produce a heavy crop of cones each year’ – Grimshaw & Bayton 2009) have continued to thrive and the best was 13.5 m tall × 34 cm dbh in 2022, while an example from Rushforth 551A planted nearby was 10.5 m × 32 cm in the same year (Tree Register 2024). Inexplicably, for the world’s self-styled leading botanical institution, all these plants are still labelled P. chihuahuana (H. Angest pers. comm. 2024). A beautiful group of trees, also from Priest 108, grow at Wespelaar in Belgium; although checked by two dry summers in a row in November 2024 the best were c. 7 m × 24 cm dbh and c. 8 m × 31 cm dbh (K. Camelbeke & J. Ossaer pers. comms. 2024). The finest of two good trees at Benmore (Argyll, UK) was 7.5 m × 18 cm dbh in November 2024 (M. Dvorak pers. comm. 2024).

Chihuahua Spruce, distributed some 640 km away to the west in southwest Chihuahua and Durango, differs in several ways. Notably: short rounded pulvini (cf. elongated in P. chihuahuana); leaves pungent but flexible (cf. pungent and stiff in P. chihuahuana); leaf colour glossy green in (cf. glaucous green in P. chihuahuana); leaf length usually 2.3–2.8 cm (cf. 1.2–2.3 cm in P. chihuahuana); leaves somewhat forward above shoot (cf. more or less radial in P. chihuahuana) and seed scales very stiff (cf. flexible in P. chihuahuana) and more densely arranged (12–16 scales per 10 cm cone length cf. 25–30 scales per 10 cm in P. chihuahuana) (Grimshaw & Bayton 2009; Debreczy & Rácz 2011). Furthermore P. martinezii typically has larger cones and seed scales than P. chihuahuana, but there is overlap in their potential dimensions and, when available, the vegetative characteristics are amply diagnostic. Only one of the recent, major phylogenetic studies have included P. martinezii in their sampling; Lockwood et al. (2013) placed it in a clade with the other North American taxa (except P. breweriana) and concluded that it was the first to diverge, occupying a somewhat isolated position within that major clade, apparently not very closely related to any of the other North American spruces.