Plant of the Month August 2025: Great Blue Lobelia

Great Blue Lobelia is a lovely late-blooming perennial in the Bellflower family that flaunts tall blue spires of flowers for weeks on end in the late summer-fall. Also called Blue Cardinal Flower or just Great Lobelia, this relative of the well-known red Cardinal Flower is native to most of eastern North America and is naturally found in moist to wet habitats such as floodplain forests, moist cove and slope forests, seeps, stream banks and bars, and wet meadows, often over limestone or calcium-rich soils. In Virginia, Great Blue Lobelia is common in the mountains, frequent in the Piedmont but infrequent in the Coastal Plain where it is always a delight to find in calcium rich soils in seeps and other moist areas such as at Dragon Run in Middlesex and Fones Cliff area in Westmoreland Counties.

From August to September, Great Blue Lobelia bears dense racemes of incredibly showy deep blue tubular flowers above 2 – 3’ tall stout leafy stems, adding vertical interest to the landscape while also supplying nectar for long tongued butterflies, bumblebees, other bees and hummingbirds. Great Blue Lobelia is named as one of the 20 key pollinator plants blooming in August and September according to the Great Southeast Pollinator Census for 2025, a citizen science project conducted annually by the University of Georgia. Their tubular flowers are larger and deeper blue than other lobelias and angled upwards along the densely packed racemes making them a knock-out in the garden and easy to identify. Individual flowers are about 1 – 1.5” long and narrowly bell-shaped with two lips – an erect, slender, upper lip with two lobes and a larger lower lip that flares out into 3 downward facing pointed lobes. Look closely and you will notice two white patches inside the corolla or throat of the flower. These showy flowers bloom for about two months, adding beauty and life to the late season landscape. In fall the flowers ripen into capsules with small seeds that often seed about.

Lobelia’s lovely lavender-blue flowers add a welcoming, long-lasting color to the late summer garden contrasting with the typical yellow blooms so abundant at this time of year. It is perfect in moist soils along ponds, streams or even rain gardens or other low damp areas but is also lovely in any garden border with rich soil or in pollinator, butterfly, or hummingbird gardens. It is also perfect for moist meadows or woodland gardens where it tolerates deep shade. Great Blue Lobelia prefers rich moist soils with plenty of organic matter in sun to deep shade but flowers best in a sunny to partly sunny site with some afternoon shade and extra water during dry spells. Growing naturally in wet seeps and floodplains, it can tolerate up to 3” of water over the roots occasionally and dense shade and is also moderately deer resistant. As a bonus, Lobelia will seed around gently in open soils where sunlight can reach the seeds. Try gently raking the soil near the base of the plant if you want to encourage reseeding and spreading.

You may have wondered about its unusual botanical name, Lobelia “siphilitica”. The renowned botanist, John Bartram, in his Medicina Britanica published in the 1700’s described the ground roots as a cure for the bacterial disease, syphilis. He learned this “cure” from Canadian Indians, and it was widely touted in the Colonies and Europe at the time but has long since been debunked and shown to be completely ineffective. As you may know, syphilis was the scourge of Europe in the early 16th centuries with many researchers having strong evidence suggesting Columbus brought this “gift” back to Europe from America in “exchange” for Columbus and other Europeans “gifting” Native Americans typhus, smallpox, measles and cholera. On a lighter note, Great Blue Lobelia as well as other lobelias, like Indian Tobacco (L. inflata), contain powerful and toxic alkaloids similar to nicotine that have been used to treat respiratory ailments such as asthma but some patients have reportedly died so it is far better to enjoy this beautiful plant in your garden and let the wildlife feast on it.

This long blooming perennial is truly gorgeous, and you will surely want to add some to your garden this fall to enjoy the tall spires of flowers as well as the hummingbirds, butterflies and pollinators that will be attracted to them.

We will have several species of Lobelia for sale at our Annual Fall Plant Sale at Good Luck Cellars in Kilmarnock: Saturday, September 6 from 12 to 3 and Sunday from 1 – 3. If you are a member of our Chapter, you can attend our member-only Presale on Friday, September 5, from 2:30 – 4:30 and get first choice of our beautiful plants. Not a member but want to be?? You can sign up on our website this month or come and join on Friday and shop the Presale. Find out more at w ww.nnvnps.org