A small, low, slender herb, perennial by short offsets; stems 6 to 20 inches long, smooth, very slender, erect or reclining, leafy and paniculately branched. Lower and basal leaves spatulate, narrowed into short petioles; upper leaves sessile and shorter. Flowers light blue, about one-third to one-half of an inch long, arranged in a loose raceme at the ends of the stems and branches on threadlike stalks as long as the flowers but not exceeding the linear-lanceolate bracts which subtend them. Calyx tube top-shaped or obovoid, half as long as the lanceolate lobes. Corolla two-lipped, the upper lip two-cleft and narrow, the lower lip cleft into three spreading lobes which are much broader than those of the upper lip. Fruit a small globose capsule, not inflated.
Memoir 15 N. Y. State Museum
B. Kalm's Or Brook Lobelia - Lobelia kalmii
On wet banks, boggy meadows and swamps, or on wet ledges of rocks about waterfalls, from Nova Scotia to New Jersey, west to Ontario, Manitoba, Ohio, Michigan and Iowa. Flowering from July to September.
The Water Lobelia (Lobelia dortmanna Linnaeus) is an aquatic perennial with numerous white, fibrous roots. Leaves linear, 1 to 2 inches long, fleshy, tufted at the base of the hollow stem and submerged. Flowers pale blue in a loose raceme at summit of the stem. Borders of ponds, from New Jersey and Pennsylvania to Newfoundland, Wisconsin and British Columbia.
The Spiked Lobelia (Lobelia spicata Lamarck) has pale blue flowers in an elongated spikelike raceme sometimes 1 to 2 feet long, each flower one-fourth to one-thrrd of an inch long. Leaves broadly oblong at base of stem, becoming spatulate higher up and finally narrowing down to linear bracts subtending the flowers. In moist or dry sandy soil, Prince Edward Island to Saskatchewan, south to North Carolina, Alabama, Louisiana and Arkansas.
Nuttall's Lobelia (Lobelia nuttallii Roemer & Schultes) is very slender. The pedicels are longer than the bracts but shorter than the small pale-blue flowers. Common in sandy swamps along the coast.