This is consistent with the observation of wild four-o clock along the interstate system of Wisconsin and probably other states as well. Weed books describe the root as fleshy but it seems to be somewhat woody under Wisconsin conditions. 4-sided but are not as square as those of plants in the mint family. Leaves are widely separated on the stem and have a short petiole. Biology Seeds are highly viable and most germinate near the parent plant.
Young taproots look much like miniature carrot roots.
The root becomes large and well entrenched as plants age. Plants resume growth each spring from crown buds. Stems branch after plants are 1 to 2 feet tall and plants flower from June to September. Wild four-o clock is named because the flowers open in late afternoon. Pollination is often done by nocturnal insects but self-pollination also occurs.