Arabis glabra (L.) Bernh.
Arabis glabra (L.) Bernh. var. furcatipilis M. Hopkins
Arabis glabra (L.) Bernh. var. glabra
Turritis glabra L.
The aptly named tower mustard is a widespread North American native plant.
Identification: I first noticed these in the late summer—tall, rigid clusters of dead sticks, lacking flowers or seeds or leaves. The “sticks” are actually seedpods. Tower mustard begins with a rosette of gray leaves, and in the second year, it produces a flowering stalk up to about 3½' (1 m) high. A few nondescript leaves alternate along the stalk, which may branch at the top into slender shoots. Small, four-petaled, cream-colored flowers, each about ¼" (6.3 mm) in size, cover some of the shoots. The shoots are siliques, narrow, rounded seedpods that look more like stems than seedpods.
Arabis glabra at Illinois Wildflowers
Arabis glabra on Calflora
Arabis glabra on Plants for a Future, a resource and information centre for edible and otherwise useful plants
Arabis glabra on CalPhotos
Arabis glabra on the Connecticut Botanical Society's Connecticut wildflowers site
Arabis glabra on the University of Massachusetts Landscape, Nursery & Urban Forestry Program
Arabis glabra at the University of Wisconsin's Robert W. Freckmann Herbarium
Arabis glabra description by Thomas H. Kent, last updated 2 Jan 2019.