Flower:

Few flowered, short racemes, about 1/3 to ½ inch long, at the tip of the stem and arising from upper leaf axils, sometimes multiple racemes in a sparsely branched cluster. Flowers are white, greenish or pinkish, about 1/8 inch long with 4 or 5 oval elliptic tepals (petals and similar sepals), and short-stalked. The stem of the raceme is 1 to 3 inches long, 4-angled with rows of stiff, claw-like, downward curving bristles along each angle.

Leaves and stems:

Leaves are alternate and triangular to arrowhead shaped with a sharply pointed tip, the edges toothless, sometimes with fine short hairs. Lower leaves are long stalked and up to 8 inches long (see notes) with two conspicuous, triangular lobes at the base that are perpendicular to the central blade (hastate). Upper leaves become smaller and more lance shaped, the basal lobes proportionately smaller, triangular but tapered to the leaf tip (sagittate). The leaf just below the flower cluster is narrowly lance shaped with a rounded taper to the base. The upper leaf surface is smooth or with sparse hairs, the lower surface usually with star-shaped hairs (stellate).

Stems are 4-angled, ribbed along the angles, with downward turned, claw like bristles along the angles. A prickled and hairy sheath (ocrea) surrounds the stem at the leaf node. Erect when young, the stems are weak and much branched above, becoming sprawling or vining on surrounding vegetation, often rooting at the nodes, and can grow to 6 feet long,

Notes:

Halberd-leaved Tearthumb, sometimes known as Polygonum arifolium or Tracaulon arifolium, is easily identified by its vining habit, leaf shape, and sparse clusters of tiny flowers. Like most of the smartweeds, P. arifolia has a high affinity for water but unlike most others, it also appears to require cool shady habitats. At the extreme northwest edge of its North American range, in Minnesota it is restricted to forested or shrubby swamps and wetlands in our east central counties and is in particular, most common in the Anoka Sandplain. While our descriptions of leaf size and stem length, taken from several standard botanical references, indicate quite large leaves and long vining stems, in our own direct observations here in Minnesota, we've never observed the leaves much longer than 4 inches and the sprawling stems rarely more than 3 feet in length.