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.org/articles/arbutus/arbutus-mexican-species/). Accessed 2021-10-15.

Genus

Glossary

cordate
Heart-shaped (i.e. with two equal lobes at the base).
crisped
Curled or crumpled.
endemic
(of a plant or an animal) Found in a native state only within a defined region or country.
entire
With an unbroken margin.
glabrous
Lacking hairs smooth. glabrescent Becoming hairless.
glandular
Bearing glands.
included
(botanical) Contained within another part or organ.
indumentum
A covering of hairs or scales.
montane
Of mountains.
petiole
Leaf stalk.
prostrate
Lying flat.
pubescent
Covered in hairs.
serrate
With saw-like teeth at edge. serrulate Minutely serrate.

Credits

Julian Sutton (2021)

Recommended citation
Sutton, J. (2021), 'Arbutus Mexican Species' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/arbutus/arbutus-mexican-species/). Accessed 2021-10-15.

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 (A. arizonica, A. occidentalis and A. xalapensis) are also given fuller treatments on their own pages. 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 arizonica (A.Gray) Sarg.

Tree 3–8(–10) m, bark grey or reddish-grey, on trunk and main branches chequered with rectangular plates, peeling on smaller branches. Current year’s stems and petioles red to pink-tinged green. Leaves usually tapered at base, glabrous beneath except on midvein. Flowers white. Western Mexico, down the Sierra Madre Occidental from Sonora and Chihuahua to Jalisco, also in the USA (SE Arizona, SW New Mexico); seasonally moist riverine forest in the north, seasonal dry montane forest further south, 1300–2800 m; fruiting August-October (Sørensen 1995, 2009). See full treatment on separate page.

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. From the 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; forest and scrub in both humid ravines and dry hillsides; in fruit all year round but mainly May–November (González, González & Sørensen 2012).

[A. glandulosa M. Martens & Galeotti]

A well known name, 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).

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. Sierra Madre Occidental, especially in Durango but extending south to Jalisco, where it is rare; forests with various Pinus and Quercus, 2050–3000 m; in fruit June to August (Sørensen 1995).

Arbutus mollis Kunth

(Syn. A. 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. Widespread in the 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); in forests with Pinus and Quercus, also clearings, 2500–3400 m; in fruit June to December (González, González & Zamudio 2012).

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. Sierra Madre Occidental, from S Chihuahua south to Jalisco; in forests, especially in areas with rocky outcrops, 2400–3200 m; in fruit April to November (González, González & Zamudio 2012).

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. 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; mountain forest with Pinus and Quercus, 1500–2850 m; in fruit (February-)April-June (Sørensen 1995).

Arbutus xalapensis Kunth

Very widespread and variable tree or large shrub, 4–6(–15) m; bark brick red, peeling in large smooth flakes except on old trunks where it may be grey and retained. Leaves 5–11 × 1.5–5 cm, usually rounded at the base, glabrous or hairy, sometimes with glandular hairs (glandular and eglandular morphs coexist in some populations). Flowers white or pinkish. Throughout Mexico except for Tabasco and the Yucatán Peninsula, extending south through Central America to Nicaragua, and north into the United States (Texas, New Mexico); in Mexico usually in mountainous country, 2000–3000 m. Fruiting follows about 6 weeks after flowering; flowering ranges from November-February in the south, to March-May in the north (Sørensen 1995, 2009). See full treatment on separate page.