Lobelia is a genus of flowering plant comprising 360–400 species, with a subcosmopolitan distribution primarily in tropical to warm temperate regions of the world, a few species extending into cooler temperate regions. English names include Lobelia, Asthma Weed, Indian Tobacco, Pukeweed, and Vomitwort.
Some botanists place the genus and its relatives in the separate family Lobeliaceae, others as a subfamily Lobelioideae within the Campanulaceae. The Angiosperm Phylogeny Group did not make a firm decision in this, listing the genus under both families.
Lobelia is probably the base form from which many other lobelioid genera are derived; it is therefore highly paraphyletic and not a good genus. For example, the Hawaiian species are part of a group including other genera that appear very different (see Hawaiian lobelioids). However, the group has not yet been studied adequately to rearrange the classification.
The genus is named after the Belgian botanist Matthias de Lobel (1538–1616).
Lobelia erinus, a South African annual plant that includes many cultivated selections in a wide variety of colours. They are grown in beds, large pots, window boxes and in hanging baskets. The plants are most often grown away from sunny hot southern exposures (northern exposure's in the southern hemisphere) in soils that are moisture retentive.
Extracts of Lobelia inflata contain lobeline, which showed positive effects in the treatment of multidrug-resistant tumor cells. Furthermore, lobeline can be modified to lobelane which decreased methamphetamine self-administration in rats. It therefore opens a perspective in methamphetamine dependency treatment.
As used in North America, lobelia's medicinal properties include the following: emetic (induces vomiting), stimulant, antispasmodic, expectorant, diaphoretic, relaxant, nauseant, sedative, diuretic, and nervine.
Because of its similarity to nicotine, the internal use of lobelia may be dangerous to susceptible populations, including children, pregnant women, and individuals with cardiac disease. Excessive use will cause nausea and vomiting. It is not recommended for use by pregnant women and is best administered by a practitioner qualified in its use.