This genus comprises about two hundred species, a few shrubby, many herbaceous and a large number annuals. The dwarf annuals are very useful for bordering flower-beds and for forming a ground-work for tall-growing specimens, for instance, a bed of the tall-growing scarlet-flowered Lobelia cardinalis with a carpet or ground-work of the dwarf blue Lobelia speciosa, making a charming combination.
They are all easily grown and thrive in any garden soil. The cardinalis type should be planted about one foot apart and the speciosa six inches apart.
The annual species are raised from seeds sown under glass; the seeds should be sown, in February, in soil composed of half leaf-mold and half light loam with enough sand to keep the compost open, the soil barely covering the seeds. The seeds being very fine, the soil for covering them should be sifted through a fine sieve. Place the pots or boxes where they have a little bottom heat; when the young seedlings are large enough to be handled, prick them out three inches apart in boxes and return them to a place with the same temperature for two weeks, when they may be placed in a cold frame and gradually hardened off, then placed out of doors until April or May, when they should be planted where they are to flower.
The Lobelia cardinalis type may also be raised from seeds, but they are generally increased by dividing the roots. This should be done in February or March.