Plants perennial herbs (annual elsewhere). Stems few to several from the rootstock, loosely ascending or creeping with ascending tips, rarely erect, sometimes rooting at the lower nodes, weakly 4-angled, hairy. Leaves usually with a partially winged petiole, variously 3-lobed to ternately or pinnately 1 or 2 times deeply divided, the segments narrowly oblong to linear, pointed at the tip, the margins sometimes coarsely few-toothed, sparsely to moderately hairy. Inflorescences terminal on the branches, not associated with slender, elongate stalks, initially dense, flat-topped clusters, becoming elongated into spikes with age. Calyces narrowly tubular, 7–13 mm long, 5-lobed, the lobes somewhat unequal in length, narrowly triangular to nearly linear, erect at flowering, becoming contorted as the fruits mature, hairy on the outer surface and along the margins. Corollas 12–30 mm long (shorter elsewhere), trumpet-shaped, slightly zygomorphic, 5-lobed, pink to lavender or light bluish purple, rarely white (red elsewhere), usually fading to dark blue, the limb 8–20 mm in diameter, the lobes often shallowly and broadly notched at the tip. Stamens inserted at 2 levels toward the tip of the corolla tube, usually with a small glandular appendage positioned laterally between the anther sacs. Ovary 4-locular, appearing 4-lobed, slightly concave at the tip. Style 15–22 mm long (shorter elsewhere), the sterile lobe extending noticeably beyond the fertile lobe (this obscured by the globose stigmatic area), flattened and narrowly triangular. Fruits consisting of (2–)4 nutlets, these more or less cylindric, usually rounded at the tip, somewhat asymmetrically concave at the base, the surface variously wrinkled, lined, and/or with a network of blunt ridges, sometimes also with small papillae, especially along the inner surface, grayish black to black (tan to brown elsewhere). About 50 species, North America to South America, Caribbean Islands; introduced in the Old World.

Traditionally, Glandularia was regarded as a section within the genus Verbena (Steyermark, 1963). Umber (1979) and Sanders (2001) have summarized morphological, cytological, and phytochemical data supporting the separation of the two groups as genera, which is how most South American botanists have been treating them for many years (Schnack and Covas, 1944).

Several species of Glandularia are cultivated as ornamentals in the Midwest, including both of the taxa growing wild in Missouri. Glandularia canadensis is popular in native plant gardening because it is easy to grow and flowers over a long period, but it can be aggressive under some conditions. Most of the other species that are cultivated in the region are grown as annual groundcovers in sunny sites. Among these, G. ×hybrida (Groenl. & Rumpler) G.L. Nesom & Pruski (garden verbena) is the most striking taxon, a complex hybrid of unconfirmed parentage (Pruski and Nesom, 1992) with relatively large flowers (calyces 10–15 mm long, corollas 25–40 mm long), with the corollas peach-colored to pink, blue, or white, but most commonly deep red. This hybrid has escaped sporadically in a number of southeastern states and eventually may be recorded as an escape in Missouri, although it does not appear to be very commonly grown in the Midwest in recent decades.

Cronquist (1991) cited the existence of moss verbena, G. pulchella (Sweet) Tronc. (as Verbena tenuisecta Briq.), as an escape in St. Louis, but the specimens upon which this report apparently was based were gathered from plants cultivated at the Missouri Botanical Garden. Thus, this widely cultivated South American species has been excluded for the present from the Missouri flora. It is somewhat similar to G. bipinnatifida, but has 2 times pinnately deeply lobed leaves with linear, tapered segments, the floral bracts shorter than the calyx (thus the spikes appearing more slender), and brown nutlets that are beaked at the tip.