1. Styles shorter than the calyx of bisexual flowers, scarcely visible; staminate flowers only 2-5, in the same umbels as bisexual flowers.

2. Calyx lobes of bisexual flowers inconspicuous, shorter than the bristles; pedicels of staminate flowers twice as long as their sepals, or shorter.

S. canadensis

2. Calyx lobes of bisexual flowers conspicuous, equaling or exceeding the bristles; pedicels of staminate flowers ca. 2-4 times as long as their sepals.

S. trifoliata

1. Styles elongate (several times as long as calyx), arching conspicuously over (or among) the bristles; staminate flowers more numerous per umbel and often in separate umbels as well as in the same ones as bisexual flowers.

3. Calyx lobes of staminate flowers soft, less than 1 mm long (usually ca. 0.5 mm) and less than twice as long as broad; mature fruit (including bristles) ca. 3-4 mm long (not including the short stalk).

S. odorata

3. Calyx lobes of staminate flowers rigid (even subulate-tipped), 1-1.6 mm long and 2-3 times as long as broad; mature fruit (including bristles) ca. 4.5-6.5 mm long.

S. marilandica