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Tree 20–30 m, 0.4–0.5 m dbh. Bark rough and grey. Branchlets densely covered in pale yellow silky hairs. Leaves evergreen, (10–)12–20(–23) × (4.5–)5–9 cm, narrowly oblanceolate to elliptic, upper surface lustrous green and glabrous, lower surface pale green to glaucous and sparsely pubescent, ~10–15 secondary veins on each side of the midrib, margins entire, apex abruptly acute to acuminate; petiole 1–4.2 cm long, glabrous; stipules linear, 4.8–7 cm long, densely covered with dark brown or yellow silky hairs. Flowers terminal, creamy white, 12–15 cm diameter; peduncle densely greenish-hairy. Sepals three, oblong-obovate, concave, 6.5–9.6 × 3–4.5 cm, whitish green; petals six, obovate, 4.5–9 × 2–4.5 cm; stamens 140–145, pale yellowish green; gynoecium sessile with (38–)53–57(–73) carpels. Fruits 5–9 × 2.3–4.5 cm, roughly ovoid; ripe carpels to 2.7 cm long, dehiscing along a dorsal suture. Flowering May to July, fruiting September (Mexico). Vázquez-G. 1994. Distribution MEXICO: Nuevo Léon (?), Tamaulipas (Sierra de Guatemala). Habitat Deciduous cloud forest in deep canyons between 700 and 1900 m asl. USDA Hardiness Zone 7. Conservation status Endangered, due to habitat loss and the gathering of firewood and floral buds for medicine. Illustration Vázquez-G. 1994; NT503. Taxonomic note This species is the closest living relative of M. grandiflora, but differs from it in several technical ways, as well as looking quite different: it has fewer carpels (38–73 vs. 75–90) and stamens (140–145 vs. >250) per flower, the outer petals are shorter (6.5–9.5 cm vs. 10.5–14.5 cm), and the lower surface of the leaf is covered in minute hairs, rather than the dense, reddish silky hairs so distinctive in M. grandiflora.
Magnolia tamaulipana is the only one of the numerous species of magnolia found in Mexico, Central and northern South America and the Caribbean to have been introduced to temperate horticulture. It has proved to be remarkably hardy, flourishing on the East Coast at least as far north as North Carolina, and on the West Coast as far north as Seattle. The earliest cultivated specimen known is in fact at the University of Washington Arboretum, from a collection made by F.G. Meyer and D.J. Rogers (Meyer & Rogers 2793) in 1948. The tree has flowered there since 1971, and is now nearly 9 m tall (Hogan 2008). It was originally labelled M. schiedeana Schlecht. – a related species with which M. tamaulipana has often been confused, but M. schiedeana is a smaller tree with glabrous branchlets, smaller flowers and fewer floral parts. In our area M. schiedeana is only in cultivation at Berkeley; Clarke (1988: S322) records that it was introduced to the United Kingdom by James Russell in 1984, but (as predicted) no plants from this introduction seem to have survived. Magnolia tamaulipana has been re-collected on several occasions since 1948, one trip by the Yucca Do Nursery team in the early 1990s yielding cuttings of an exciting narrow-growing form with purple-bronze new leaves. This has been named ‘Bronze Sentinel’ and is proving an excellent garden plant of considerable hardiness, unaffected by frost to –18 °C, although it will be damaged by persistent lower temperatures. It seems to be a bit hardier than other clones, which can be damaged at –12 °C. This surprising tolerance to cold is explained by the fact that weather fronts carrying cold air from Canada can sometimes reach central Mexico, to the extent that many species there are well adapted to cold (Hogan 2008). The other side of the coin, however, is that M. tamaulipana does appreciate a hot summer to flourish.
It is inevitable that comparisons with M. grandiflora will be drawn. Magnolia tamaulipana has the advantage of bronzed or coppery new leaves, but in most clones the growth is a bit gawky, not forming a solid mass of foliage. The flowers are large and sweetly scented, but narrower in outline than those of M. grandiflora, with the tepals being a dirtier white and pinkish brown on their exterior surfaces. If there were no comparison to be made the Mexican would be considered dashingly handsome, but in a straight contest the Southern Belle retains her crown.