Ulmus americana 'St. Croix'
The American Elm cultivar Ulmus americana 'St. Croix' is a recent (2008) selection cloned from a large tree growing on a farm near Afton, Minnesota, which has displayed a high resistance to Dutch elm disease (DED). A U S patent, PP 20097, was granted in 2009. Description ‘St. Croix’ has an open-grown, spreading, vase-shaped crown. The growth rate is fast and typical of the species in Minnesota. The bark is typically divided into grayish, flat-topped ridges, which are separated by roughly diamond-shaped fissures and which become indefinite in pattern in the canopy. Bark on young branches is smooth with inconspicuous lenticels. The twigs are slender, zigzag, brown, glabrous or slightly pubescent; lateral buds are about 6 mm long, ovoid, acute but not sharp-pointed, smooth or sparingly downy, chestnut-brown. Leaves are deciduous, simple, alternate, short-petioled, 2-ranked, dark green (closest to 006600 on HTML True Color Chart), 10–15 cm (4–6 inches) long, 2.5–5 cm (1–2 inches) wide and oblong-obovate to elliptical, the margin coarsely doubly serrate, the apex acuminate while the base is typically inequilateral; surfaces glabrous (smooth) or slightly scabrous (roughened) above, usually pubescent below; veins alternate, ascending, parallel and extending from central vein to apex of longest serrations. The perfect