Arbutus Mexican Species
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Credits
Julian Sutton (2021)
Recommended citation
Sutton, J. (2021), 'Arbutus Mexican Species' from the website Trees and Shrubs Online (treesandshrubsonline.
Infraspecifics
Articles in Group
Every Arbutus species native to the Americas, except A. menziesii, is either endemic to Mexico or has part of its range there. They have proved taxonomically challenging, and several species have been described or reinstated in recent decades. Our aim here is to summarize their identification features and distributions, to aid the understanding of cultivated material originating in Mexico.
Those species known to be grown in our area (Arbutus arizonica, A. occidentalis and A. xalapensis) are receive full treatments on their own pages.
The well known name Arbutus glandulosa M. Martens & Galeotti has been reduced to synonymy with A. xalapensis, of which it is merely a glandular-hairy morph Sørensen (1995). The name was frequently applied to specimens of A. bicolor before that species was recognized (González, González & Sørensen 2012). Some plants from western Mexico identified as A. glandulosa (McVaugh & Rosatti 1978) may represent the glandular-hairy A. tessellata (González, González & Sørensen 2012).
For further information, first see Sørensen (1995); González, González & Sørensen (2012) and González, González & Zamudio (2012) describe two more species and greatly change the delineation of a third, while Sørensen (2009) further discusses those whose ranges extend north into the United States. Numerous natural hybrids have been recorded, usually very locally, sometimes as swarms.
Arbutus bicolor S.González, M.González & P.D.Sørensen
Tree 4–25 m, closely related to A. xalapensis, its bark peeling in smooth flakes to reveal pink to cinnamon-red underbark except on the oldest trunks, where grey, chequered and retained. Distinguished from all other Mexican species by the lower leaf surface being completely covered by a creamy indumentum of tightly curled hairs, contrasting with the dark green upper surface (in others hairs are neither tightly curled nor obscuring the lower surface, upper surface various shades of green); glandular hairs clearly visible on the petioles. Leaf bases cordate to rounded. Flowers pink, rarely white. In fruit all year round but mainly May–November (González, González & Sørensen 2012).
Distribution Mexico Sierra Madre Occidental in Chihuahua and especially Durango, through the Sierra Volcánica Transversal to the the western slopes of the Sierra Madre Oriental in Hidalgo and Puebla
Arbutus madrensis S.González
Tree 2–9(–15) m, bark dark grey with chequered plates, not peeling except on the smallest branchlets. Leaves large, 8–15 × 5–9 cm (cf. A. xalapensis), dark green above, pubescent beneath, usually rounded at the base. Flowers white; in fruit June to August (Sørensen 1995).
Distribution Mexico Sierra Madre Occidental, especially in Durango but extending south to Jalisco
Arbutus mollis Kunth
Synonyms
Arbutus occidentalis var. villosa McVaugh & Rosatti
A spreading or sometimes upright shrub, variable, and apparently more closely related to A. xalapensis than to A. occidentalis but until recently included in the latter species; 0.2–1.2(–2) m, prostrate branches sometimes rooting; bark red-brown, peeling in small flakes. Leaf densely hairy beneath, especially when young – some plants have glandular hairs, in others they are eglandular; margin entire or sparsely serrate; petiole pubescent above and below; leaf base variably shaped. Flowers white to pink; in fruit June to December (González, González & Zamudio 2012).
Distribution Mexico Sierra Volcánica Transversal, also in the Sierra Madre del Sur (Guerrero), the Sierra Madre Oriental (Hidalgo), and less certainly in the Sierra Madre Occidental (S Durango)
Arbutus occidentalis McVaugh & Rosatti
A spreading shrub 0.2–0.5(–0.8) m, branches sometimes rooting; bark red-brown, peeling in small flakes. Leaf usually glabrous beneath, even when young; margin finely and evenly serrate; petiole pubescent only on upper side; leaf base variably shaped. Flowers pink or blush, rarely white; in fruit April to November. (González, González & Zamudio 2012).
Distribution Mexico Sierra Madre Occidental, from S Chihuahua south to Jalisco
Arbutus tessellata P.D.Sørensen
Tree or large shrub to 6(–15) m, bark pale grey with chequered plates, not peeling except on small branchlets. Leaf surfaces and (very clearly) petioles with both glandular (average length 2.5 mm) and shorter, crisped, eglandular hairs; upper surface olive, lower paler green; base variably shaped; flowers white or yellowish; in fruit (February-)April-June (Sørensen 1995).
Distribution Mexico Sierra Madre Occidental from Chihuahua to Jalisco, then east along the northern slopes of the Sierra Volcánica Transversal to W Veracruz, as far south as SE State of México