Acer skutchii Rehder

The most southerly member of the sugar maple complex, Acer skutchii was described by Alfred Rehder from Guatemalan material (Rehder 1936), and has been variously treated as a subspecies of A. saccharum and at species rank since. New light has been shed on its state in the wild as a result of work led by Yalma Vargas-Rodriguez and colleagues at the University of Guadalajara, from which a new species, A. binzayedii Y.L.Vargas-Rodr. has been described (Vargas-Rodriguez et al. 2017) from material previously referred to as part of A. skutchii (Vasquez Garcia et al. 2000). This grows at the University of Guadalajara campus (pers. observation) and is included in the key to this group (for which see the account of A. saccharum) but is yet to be tried in collections within our study area. Vargas-Rodriguez et al. (2020) have studied the populations of the sugar maples in Mexico, and contrary to the distribution provided by van Gelderen et al. (1994) (and referred to by Grimshaw & Bayton (2009) in New Trees) subspecies floridanum and saccharum do not extend south of the US border.

Acer skutchii is grown in the southeastern United States from collections made in Tamaulipas, Mexico, by Yucca Do Nursery (Grimshaw & Bayton 2009), including specimens at SFA Gardens (Stephen F. Austin State University), Texas. The oldest here was planted in 1994 and by 2016 had made 14 m, with an oval crown (Creech 2016). Exhibiting strong marcescent tendencies, it only began to show any autumn colour following flowering for the first time after nine years in the ground, its colour since varying from yellow to red (Creech 2016). Using open-pollinated seed from this tree, research plots were established in 2011 at Stephen F. Austin State University’s Science Research Center. Performance is somewhat variable, and growers of the same material elsewhere in the southeast have had mixed experiences. One correspondent describes it as ‘hideous in form, growing off at all trajectories like a North Korean rocket test’ (Creech 2016). A young, transplanted specimen at Houston Botanic Garden put on a surprising amount of growth – nearly a metre – in its first summer after moving, though older transplanted specimens have experienced shock on being moved, as expected (de la Mota, pers. comm. 2022). Potential for offspring from the SFA gardens trees to be hybridised is acknowledged, with A. floridanum growing in the vicinity (Creech 2016), and plants growing at Westonbirt from seed collected from this same parent show hybrid characters. Planted in 2013, these stand at approximately 9 m tall in January 2024, growing at a quicker rate than other young sugar maples in the collection (pers. obs.) and retaining most of the previous year’s foliage. Autumn colour on these plants is unspectacular, so far at least.

Grimshaw & Bayton (2009, p. 106) describe material matching Acer skutchii in the western United States as having ‘large leathery leaves that persist into the New Year, when they colour red and fall slightly before or as the new leaves emerge, thus making the tree almost evergreen’. These authors note that there is a good specimen in the Hogan–Sanderson plantings in Northeast 11th Avenue, Portland, Oregon.

A 1995 planting of the species grows at Tregrehan, Cornwall, UK and measured 5 m in 2014 (The Tree Register 2023), having stood at 2 m in 2007 (Grimshaw & Bayton 2009). Grown from a John Fairey collection (The Tree Register 2023), it was planted in a sheltered location in the belief that it was tender, though the species has been reported to tolerate temperatures as cold as –18ºC (Grimshaw & Bayton 2009) becoming deciduous in the coldest spells (Hogan 2008). A specimen from another John Fairey collection grows at Whitehouse Farm, Kent, UK and having been received as seed in 1992 is the current UK champion, standing c. 8 m tall (J. Aldridge, pers. comm. 2023). Seemingly proving completely hardy, the species is also tolerant of heavy clay soils (Raulston 1996).