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Sacred lily (Rohdea japonica)





Perennial Lobelia – Old Strains and New Cultivars
by Caleb Melchior - posted 06/19/12

Does your garden have a soggy spot that needs a blaze of color? Whether you have a garden bed beneath a downspout that never dries out or a planter that somehow just gets watered too often, plant a perennial lobelia. Nothing like the tiny blue annuals that disappear when summer heats up, perennial lobelias are a group of upright plants with towers of vibrant bloom.

Two species are native to damp meadows and streamsides throughout the Eastern United States.

Cardinal flower (Lobelia cardinalis) is a reliable perennial for damp areas, with crimson blooms that are highly attractive to hummingbirds.

Bird lovers will want to plant the cardinal flower (Lobelia cardinalis). In midsummer, the 2-foot rosettes of narrow foliage erupt with 3- to 5-foot spikes of scarlet bloom. While named for its flower color, cardinal flower could just as easily be called “hummingbird plant.” Its tubular scarlet flowers seem to have been custom-designed for the little jewel birds.

The great blue lobelia (Lobelia siphilitica) is the blue version. It is unfortunate botanical name references a past belief that it could be used as a cure for syphilis. Time has, however disproved that theory. Its lack of pharmaceutical properties, however, is made up for in its virtue as a garden plant. It’s a stockier plant than cardinal flower, with clumps 3 to 4 feet high and 2 to 3 feet wide. Flower color is highly variable, ranging from washy gray-violet to vibrant blue. Flowering is heaviest in midsummer and continues sporadically until fall. While officially perennial, a single lobelia plant rarely survives more than two growing seasons. However, the original plant’s place will be quickly filled by the abundance of self-sown seedlings.

Lobelia ‘Fan Scarlet’ is a dwarf variety with rich red flowers.

Because lobelias tend to be short-lived, even in the best growing conditions, traditionally propagation has been primarily by seed. Seed strains were selected for heavier flowering and stronger flower color. The most common strains are found in the Fan series, with colors including blue, burgundy, salmon and scarlet. They are well known for their compactness and strong bloom. They rarely grow more than 2.5 feet tall and bloom for much of summer and into the autumn. The Compliment series includes deep pink, ruby and scarlet. They grow a little taller, to 3 feet, with abundant flower stalks. These seed strains vary widely in hardiness, with gardeners throughout the country having mixed results, especially in Zones 5 to 7. Expect them to be annual and enjoy encore performances.

Development of tissue culture technology has enabled mass propagation of individual clones. While the two species are highly variable and seed strains offered only moderate uniformity, tissue cultured clones have uniform traits like compact habits, heavier flowering, and a wider range of foliage and flower color.

Lobelia 'Monet Moment' brings exquisite bright pink flowers to soggy spots in midsummer.

Thurman Maness of North Carolina was the most prolific breeder and introducer of perennial lobelia cultivars in the United States. Probably his most widely distributed cultivar is ‘Monet Moment’, with sensational towers of bright pink flowers. We have grown it in our bog gardens at the nursery for three years. In Zone 6, we have found that, while plants do return from year to year, flowering is heavier if they are treated as annuals and planted fresh every year.

Another cultivar that blends the strong color of both native species and combines them in one dynamite package, ‘Grape Knee-High’ is a dwarf cultivar with blatant grape purple flowers. It reaches barely 2 feet high and wide, with brighter green foliage than many varieties. It is winter-hardy, reliably returning as far north as Zone 5.

Moving from cultivars grown for their flowers to those with dramatic foliage color, ‘Golden Torch’ surprised us with its vigor and tolerance of heat and humidity. Its bright chartreuse foliage made it stand out, both on the nursery benches and in the garden. Flowering stems reached 3 feet, with basal foliage 1 foot wide. Like many clones, ‘Golden Torch’ performs best if used as an annual.

At the complete opposite end of the color spectrum, ‘Queen Victoria’ is an old selection with fantastic deep purple foliage. However, it is not reliably hardy north of Zone 7. Its strong color and vigorous growth make it worth growing as an annual in the rest of the country. If perenniality is more important than color, try ‘Fried Green Tomatoes’. It is vigorous and seems to be more reliably perennial (to Zone 5) than ‘Queen Victoria’, but its foliage is nowhere near as dark. With lightly bronzed foliage, it fits into planting schemes without overwhelming its surroundings.

For a strong statement with foliage or flowers, try a new perennial lobelia cultivar. Their vibrant colors will jolt your garden out of the midsummer doldrums. Soggy spots need never be colorless again.

(Photos courtesy of Caleb Melchior.)


Caleb Melchior has extensive experience with growing perennials after working at a specialty perennial nursery, Sugar Creek Gardens, in Kirkwood, Missouri. He is currently studying for a master’s degree in landscape architecture at Kansas State University.