Lobelia is a large genus of about 370 different species of annuals, perennials, water plants, and even shrubs, all of whose flowers have the characteristic lobelia shape, with 3 lower fan-like petals and two upright petals on top.  Depending on what type you are growing, flowers can be blue, purple, red, white, or pink.  There is a lobelia for almost every landscape purpose, including window boxes and other containers, borders, perennial or annual bed fillers, and water garden accents.  

Relatively few of the many Lobelia types are readily available to the home landscaper, and only two will be featured here, the upright Cardinal Flower and the short Edging Lobelia.  Lobelias encompass some of the most brightly colored flowers in the spectrum, and in my opinion are vastly underused in today's landscape. 

Cardinal Lobelia or Cardinal Flower:  Most of us are familiar with this hardy perennial and it's crimson red (or blue or white) flowers that grow up to 3 feet tall.  Cardinal Flower  is native to the Eastern US and is often seen growing wild along shady stream banks. Stems and leaves have a purple tinge, and flowering occurs in mid to late summer with blooms lasting a surprisingly long time.  This is a good plant for the moist banks of a backyard water garden or low spot in the landscape that other plants would find a bit too damp.  As noted above, Cardinal flower does well in shady areas, where it will provide a bright boost of color where it's needed most, especially the red versions.   Cardinal flower has few pests, is hardy to Zone 3, and needs little maintenance, however, cutting off declining flower stalks as time permits is never a bad idea. This keeps the scene fresh and the plants blooming.  One point that should be made here is that Cardinal Flower is pretty much a short-lived perennial.  It might come back for a few years, and then suddenly fail.  Always propagate new plants every couple of  years by leaving spent flowers so the plant can reseed itself, or by stem cuttings or planting store-bought seed.   The winter rosettes can be divided in the fall, if this is your preferred method.  Lastly, Cardinal Flower is a hummingbird magnet, so stand back!

Lobelia Erinus, also known as Edging Lobelia, Trailing Lobelia, and Garden Lobelia:   This Lobelia is popular because of its summer-long flowering habit in a range of colors from white to pink to red to shades of blue and purple.  It is grown as a perennial in very warm climates, and as an annual in colder areas.  It grows up to only about 6 inches and forms a clump or mat that can grow to a foot or so wide.  It prefers full to partial sun and moist but well-drained soil.  Trim back a little anytime the plant starts looking tired to rejuvenate it.  Edging Lobelia is a cascading plant that does well in hanging containers and window boxes, and also works well as an edging plant for an annual or perennial border or pathway. The flower pictured above is "Crystal Palace" Lobelia that I grew from seed. 

Again, there are many more Lobelia selections out there, so never hesitate to try a new one if you run across it.  Remember, Lobelia is easy to spot because of the bright flower colors and the configuration of the flower petals, with 3 larger fan-like petals below and two upright petals on top.  See the links on top right for other uses for this valuable plant.