Siberian Elm:  Ulmus pulmila. This elm is distinguished by its small, elliptical, smooth, singly-toothed leaves, that reach lengths of 0.8-2.6 inches. They are tapering or rounded at their asymmetrical base. The alternate leaves are dark green and smooth above, paler and nearly hairless beneath. Foliage is slightly pubescent when young. Flowers are greenish, lack petals, and occur in small drooping clusters of 2-5 blossoms. The winged fruits are about 1/2-inch-wide and hang in clusters.

Tree-of-Heaven:  Ailanthus altissima. Originally from China; rapid growing tree to 80 feet tall; alternate, compound leaves, 10-40 leaflets with smooth margins on 1- to 3-foot stalks. Large terminal clusters of small yellowish-green flowers yield wing-shaped fruit on female trees. Forms thickets and dense stands.

Salt Cedar:  Tamarix spp. Salt cedars are characterized by slender branches and gray-green foliage. The bark of young branches is smooth and reddish-brown. As the plants age, the bark becomes brownish-purple, ridged and furrowed. Leaves are scale-like, about 1/16 inch long and overlap each other along the stem. They are often encrusted with salt secretions. From March to September, large numbers of pink to white flowers appear in dense masses on 2-inch long spikes at branch tips.