Flower:

White flowers, 1/3 to ½ inch across with 4 rounded petals grow at the tips of numerous, elongating racemes that form a tight, showy cluster.

Leaves and stems:

Basal leaves are large, long stalked, generally oblong (rarely lobed) with blades up to 12 inches long and 5 inches across, typically heart-shaped at the base. Leaf edges are wavy with small, rounded teeth, the leaf surfaces glossy and hairless.

Leaves become smaller, narrower and shorter stalked as they ascend the stem, the upper leaves lance-linear with little or no stalk and sometimes toothless. One or more stems emerge from the basal cluster, branching in the flower cluster.

Fruit:

Pods are small and oval on ascending stalks, but mostly absent as seeds rarely mature.

Notes:

Native to southeastern Europe and western Asia, horseradish was introduced as garden crop, well known for the pungent sauce made from its root. Now escaped into the natural environment, in Minnesota it is increasingly common along grassy road rights-of-way throughout the state, though likely is under-reported. When not in flower the basal leaves may resemble one of the docks, but otherwise it is not likely to be confused with other species having 4-petaled white flowers.