ULMACEAE

ELM FAMILY

Dieter H. Wilken

Shrub or tree, often monoecious
Leaves simple, generally alternate, generally 2-ranked, short-petioled; stipules deciduous; blade base often oblique, veins pinnate
Inflorescence: cyme, clustered, axillary; flowers 1–few; bracts 0
Flower radial; sepals 4–6, free to fused; corolla 0; stamens 4–6, opposite sepals; ovary superior, chamber 1, ovule 1, style branches generally 2
Fruit: drupe or winged nutlet
Genera in family: ± 15 genera, ± 150 species: temp to tropical; some cultivated for ornamental (Celtis , Ulmus , Zelkova ), some used for wood, fibers (especially Ulmus )
Reference: [Elias 1970 J Arnold Arbor 51:18–40]
Recent taxonomic note: Celtis recently treated in Celtidaceae [Angiosperm Phylogeny Group 1998 Ann Missouri Bot Gard 85:531–553; Wiegrefe & Sytsma 1998 Plant Syst Evol 210:249–270]

ULMUS

ELM

Shrub or tree
Stem: trunk bark scaly to furrowed, gray to brown
Leaf serrate (or doubly so), base generally oblique, obtuse to cordate
Inflorescence sessile to short-stalked
Flower bisexual; calyx generally bell-shaped, lobes 5–9; stamens 5–9, exserted; style branches spreading
Fruit: nutlet, compressed, clearly winged
Species in genus: ± 20 species: n temp; some widely cultivated (e.g. U. americana , american elm, U. X hollandica , dutch elm).

Introduced

U. pumila L.

SIBERIAN ELM

Tree generally < 10 m
Stem: twigs glabrous to sparsely puberulent
Leaf: blade 3–9 cm, narrowly elliptic to lanceolate, margin generally singly serrate, glabrous (lower surface vein axils puberulent)
Inflorescence: flowers appearing before leaves in spring
Flower: calyx lobes short, unequal
Fruit 10–15 mm, 10–12 mm wide; body 2–4 mm wide; wing translucent, whitish
Ecology: Waste places, roadsides, washes
Elevation: < 1800 m.
Bioregional distribution: Sierra Nevada Foothills, Great Central Valley, East of Sierra Nevada, n Mojave Desert
Distribution outside California: to c US; native to c Asia
Flowering time: Spring
Cult; reproducing by seeds and root-sprouts.