Leaves and stems:

The sterile stem is green and usually has no branches, though short stubby branches may develop on some plants. The “leaves” are reduced to a sheath that surrounds the stem, with 10 to 32 black teeth around the top. The teeth fall off as the season progresses, leaving a thin dark ring around the top of the sheath.

The stem is firm, the central cavity mostly ½ to ¾ the diameter of the stem.

Fruit:

Fertile stems are like sterile stems, but with a ½ to 1 inch long cone at the tip of the stem. Cones have a blunt tip or may have a tiny, inconspicuous sharp tip.

Notes:

Smooth Scouring Rush is one of three similar, unbranched Equisetum species in Minnesota, the others are Tall Scouring Rush (E. praealtum, a.k.a. E. hyemale) and Variegated Scouring Rush (E. variegatum). In the early part of the season, E. laevigatum can be identified by the entirely black teeth; later in the season by the lack of teeth and the dark ring around the top of the sheath. E. praealtum also has black teeth but has a black band around the base of its pale gray sheath and often the tip as well. E. variegatum is further distinguished by its fewer and larger persistent teeth with distinct white edging. E. laevigatum hybridizes with E. praealtum, producing E. × ferrissii, and with E. variegatum, producing E. × nelsonii.