Rock elm (Ulmus thomasii)
Height 60' to 70', diameter 24" to 48"; straight trunk; somewhat conical head with long, graceful branches.
Ash gray; divided by deep fissures into broad, flat ridges; outer bark layers alternating white and brown in cross section.
Simple, alternate on stem, length 2" to 4"; deep green, doubly toothed margins, uneven base; turns yellow in autumn.
Winged samara, 1/2" long; ovate, waferlike, contains one seed, slightly notched at outer end; ripens in early summer.
Commonly found on bottomlands in the eastern and south- central parts of the state, especially in the Minnesota River Valley, and continues as far northward as Clearwater County. Moderately shade tolerant, fast growing.