Lobelia (Lobelia) is available in annual and perennial varieties, though both have tubular blooms, similar to those on honeysuckle. The annual variety (L. erinus) may be grown in any U.S. Department of Agriculture plant hardiness zone during the warmer months, while the perennial varieties are generally suited for zones 2 to 9 and cannot stand extreme cold or subtropical climates. Lobelia thrives in full sun to part shade in hotter climates and requires ample water.
Cardinal Flower (L. cardinalis) is a perennial that is native to the Northeast but is also found in some mountainous areas of the Southwest. This variety of Lobelia grows to 4 feet and has saw-edged leaves and flame-red flower spikes in summer. Cardinal Flower should be planted in rich, organic soil and needs constant moisture, and may be planted in zones 2 to 9.
This annual variety is often used as an edging plant that may be compact or trailing. L. erinus usually produces blue or violet blooms with yellow highlights in the throat and should bloom in the summer. It may be a perennial in warmer climates, but it should be planted as a spring annual in areas that have mild winters or hot, humid summers. This Lobelia is a good selection for containers, as the trailing kind will spill over and blooms will hang over the sides.
This perennial variety of Lobelia is a hybrid that can grow to 4 feet and produces blooms in many colors. The "Vedrariensis" has coppery-green leaves and bright purple flowers, while the "Rosea" cultivar reaches only about 2 1/2 feet and produces rose-pink blooms. L. gerardii thrives in rich, organic soil and needs constant moisture. This Lobelia may be planted in zones 4b to 9.
This perennial Lobelia, known as "Great Blue Lobelia," is native to the eastern part of the U.S. and usually produces blue flower spikes, though some cultivars have white or rose-colored flowers. The foliage is particularly leafy, and the plant will grow to about 3 feet. L. syphilitica thrives in partial shade and requires ample moisture. This Lobelia may be planted in zones 3 to 9.