This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Lobelia Dortmanna L. Sp. Pl. 929. 1753.
Perennial, aquatic, glabrous throughout, somewhat fleshy; roots numerous, white, fibrous; stem slender, simple, erect, hollow, minutely scaly, 6'-18' high. Leaves all submersed and tufted at the base of the stem, terete, hollow, obtuse, longitudinally divided by a partition, 1'-2' long, about 2" thick; flowers in a loose terminal raceme, blue, 6"-8" long; pedicels filiform, shorter than or equalling the flowers; calyx-lobes subulate or lanceolate, shorter than the tube, the sinuses usually not at all appendaged; corolla-tube 3"-4" long, its lower lip glabrous or nearly so.
Borders of ponds, usually in sandy soil, sometimes wholly emersed when the water is low, New Jersey and Pennsylvania to Newfoundland, Wisconsin, Washington and British Columbia. Also in Europe. July-Sept.
Lobelia paludosa Nutt. Gen. 2: 75. 1818.
Perennial, aquatic, glabrous throughout; roots few and thick; stem nearly naked, slender, simple, or branched above, 1°-4° high. Leaves mostly tufted at the base, flat, narrowly oblong or spatulate, emersed, obtuse or acutish, entire or repand-denticulate and glandular, those of the stem few, small and sessile, the basal ones 2'-9' long, 2"-4" wide, narrowed into petioles; flowers pale blue, racemose, 5"-6" long; calyx-lobes narrowly lanceolate, about as long as the tube, the sinuses commonly not at all appendaged; corolla-tube 3"-4" long, its lower lip pubescent at the base.
In swamps and ponds, Delaware to Florida and Louisiana mostly near the coast. May-July.
Lobelia cardinalis L. Sp. Pl. 930. 1753.
Perennial by offsets; stem slightly pubescent, or glabrous, leafy, simple or rarely branched, 2°-4 1/2° high. Leaves oblong, oval, ovate-lanceolate, or lanceolate, thin, glabrous or sparingly pubescent, 2'-6' long, 1/4'-1 1/2' wide, acuminate or acute at both ends, crenulate or denticulate, the upper sessile, the lower petioled; flowers racemose, commonly numerous, bright scarlet or red (rarely white), 1'-1 1/2' long; bracts usually glandular; calyx glabrous or pubescent, its lobes linear, elongated, acute; corolla-tube nearly or quite 1' long; larger anthers glabrous.
In moist soil, New Brunswick to Florida, Ontario, Kansas, Colorado and Texas. Slink-weed. Hog's-physic. July-Sept.
Lobelia syphilitica L. Sp. Pl. 931. 1753. Lobelia syphilitica ludoviciana A. DC. Prodr. 7: 377. 1839.
Perennial by short offsets; stem sparingly pubescent, rather stout, very leafy, usually simple, 1°-3° high. Leaves glabrous or sparingly puberulent, 2'-6' long, 1/2'-2' wide, oval, oblong, or lanceolate, acute or acuminate at the apex, narrowed at the base, re-pand-denticulate, irregularly crenate-dentate or nearly entire, sessile, or the lower obovate, obtuse and narrowed into petioles; flowers bright blue, or occasionally white, 10"-12" long, densely racemose, leafy-bracted; calyx-lobes lanceolate, acuminate, pubescent or ciliate, the sinuses appendaged by large deflexed auricles; corolla-tube 5"-6" long, about 2' thick, the lobes of its larger lip oblong-oval, obtuse or acutish, glabrous; larger anthers glabrous.
In moist soil, Maine and Ontario to South Dakota, Colorado, Georgia, Louisiana and Kansas. Hybridizes with the preceding species. High-belia. July-Oct.