Flowers are approximately 3 mm. in length and are light pink in color. Each bloom has 4-6 sepals but are completely absent of petals forming slightly ovate grain-like structures. Flowers are arranged in elongated clusters approximately 1.5-6.5 cm. in length and varying in width.
The lens-shaped fruit are small, concave, and two-sided.
The leaves of the pennsylvania smartweed are narrowly lanceolate and long, measuring approximately 10-15 cm. in length, and are sparsely covered in short hairs. These leaves are easily identified by a prominent dark green smudge spanning perpendicularly across the half-way point of the light green mid-vein. However, this marking is sometimes absent and often apparent on other species of wildflower, A light-green sheath surrounds the stem at every petiole-stem fusion point. Leaves are arranged in an alternate fashion below the flower cluster.
Pennsylvania smartweed grows best in damp clearings, along roadsides, and around waste areas.
Pennsylvania smartweed, along with various other species of smartweed are a part of the buckwheat family. By this, they are a popular and reliable food source for many animals.
Pennsylvania smartweed is a competitor of commercial crops such as cereals, berries, and vegetables. The small seeds of this plant are often found as contaminants within commercial grain.
Other names attributed to Pennsylvania smartweed include Japanese knotweed.