Lobelia Species, Blue Cardinal Flower, Great Blue Lobelia

Lobelia siphilitica

Family: Campanulaceae (kam-pan-yew-LAY-see-ee) (Info)
Genus: Lobelia (low-BEE-lee-a) (Info)
Species: siphilitica (sigh-fy-LY-tih-kuh) (Info)
Synonym:Dortmanna siphilitica
View this plant in a garden



Water Requirements:

Requires consistently moist soil; do not let dry out between waterings

Very high moisture needs; suitable for bogs and water gardens

Sun Exposure:

Sun to Partial Shade

Light Shade




Foliage Color:

Unknown - Tell us


24-36 in. (60-90 cm)


18-24 in. (45-60 cm)


USDA Zone 4a: to -34.4 C (-30 F)

USDA Zone 4b: to -31.6 C (-25 F)

USDA Zone 5a: to -28.8 C (-20 F)

USDA Zone 5b: to -26.1 C (-15 F)

USDA Zone 6a: to -23.3 C (-10 F)

USDA Zone 6b: to -20.5 C (-5 F)

USDA Zone 7a: to -17.7 C (0 F)

USDA Zone 7b: to -14.9 C (5 F)

USDA Zone 8a: to -12.2 C (10 F)

USDA Zone 8b: to -9.4 C (15 F)

USDA Zone 9a: to -6.6 C (20 F)

USDA Zone 9b: to -3.8 C (25 F)

Where to Grow:

Grow outdoors year-round in hardiness zone

Can be grown as an annual


All parts of plant are poisonous if ingested

Bloom Color:

Dark Blue


Bloom Characteristics:

Unknown - Tell us

Bloom Size:

Unknown - Tell us

Bloom Time:

Mid Summer

Late Summer/Early Fall

Other details:

Unknown - Tell us

Soil pH requirements:

6.1 to 6.5 (mildly acidic)

6.6 to 7.5 (neutral)

Patent Information:


Propagation Methods:

By dividing the rootball

From seed; stratify if sowing indoors

From seed; sow indoors before last frost

Seed Collecting:

Allow pods to dry on plant; break open to collect seeds

Properly cleaned, seed can be successfully stored


This plant is said to grow outdoors in the following regions:

Auburn, Alabama

Castro Valley, California

Denver, Colorado

Cornwall Bridge, Connecticut

Simsbury, Connecticut

Wilmington, Delaware

Anna, Illinois

Aurora, Illinois

Divernon, Illinois

Itasca, Illinois

Mount Prospect, Illinois

Rockford, Illinois

Wilmette, Illinois

Winnetka, Illinois

Bloomington, Indiana

Jeffersonville, Indiana

Logansport, Indiana

Macy, Indiana

Valparaiso, Indiana

Cedar Falls, Iowa

Derby, Kansas

Shawnee Mission, Kansas

Brandenburg, Kentucky

Hebron, Kentucky

Baltimore, Maryland

Potomac, Maryland

Silver Spring, Maryland

Sharon, Massachusetts

Erie, Michigan

Lake Orion, Michigan

Pinconning, Michigan

Royal Oak, Michigan

Andover, Minnesota

Hopkins, Minnesota

Saint Paul, Minnesota(2 reports)

Byhalia, Mississippi

Florence, Mississippi

Cape Girardeau, Missouri

Cole Camp, Missouri

Piedmont, Missouri

Saint Louis, Missouri

Hudson, New Hampshire

Munsonville, New Hampshire(2 reports)

Browns Mills, New Jersey

Frenchtown, New Jersey

Averill Park, New York

Bronx, New York

Buffalo, New York

Croton On Hudson, New York

Glens Falls, New York

Indian Lake, New York

Schenectady, New York

Syracuse, New York

Yonkers, New York

Chapel Hill, North Carolina

Elizabeth City, North Carolina

Belfield, North Dakota

Columbus, Ohio

Fremont, Ohio

Glouster, Ohio

Guysville, Ohio

Allentown, Pennsylvania

Coopersburg, Pennsylvania

Greensburg, Pennsylvania

Lawrenceville, Pennsylvania

Lehigh Valley, Pennsylvania

Philadelphia, Pennsylvania

Saylorsburg, Pennsylvania

West Chester, Pennsylvania

Wilkes Barre, Pennsylvania

Conway, South Carolina

Murfreesboro, Tennessee

Old Hickory, Tennessee

Austin, Texas(2 reports)

Dallas, Texas

Huntsville, Texas

Longview, Texas

Quechee, Vermont

Arlington, Virginia

Leesburg, Virginia

Lexington, Virginia

Pearisburg, Virginia

Richmond, Virginia

Roanoke, Virginia

Kalama, Washington

Pullman, Washington

Cambridge, Wisconsin

Madison, Wisconsin

Pleasant Prairie, Wisconsin

show all

Gardeners' Notes:


On Sep 2, 2018, jep1978 from Shorewood Hills, WI wrote:

This is an appealing eastern U.S. native plant with purple-to-blue, intricately-shaped flowers. I also like that it flowers in late summer, when not much else on my land is blooming.

Contrary to most descriptions, I've repeatedly seen this plant in mostly shaded, moist but not wet woodlands. This includes my own property, where I'm starting to notice small plants in flower two years after seeding.

I don't find it to be at all aggressive.


On Aug 27, 2018, flwrgrl4444 from Niskayuna, NY (Zone 4b) wrote:

This plant is extremely aggressive in my area. It crowds out all my other plants. Now the neighbors got it and it is spreading throughout the neighborhood. Easy to pull out, but it reseeds itself so it is very difficult to truly get rid of it. If you like a messy looking garden, then this plant is for you.


On Aug 9, 2016, coriaceous from ROSLINDALE, MA wrote:

In the wild, this is a wetland plant. But in my experience, it performs well in ordinary moist well-drained garden conditions, and it doesn't seem any less drought tolerant than most ordinary garden plants. If you're going to skimp on irrigation in a drought, it does need some shade. Mine is a clump-former, not at all aggressive or invasive, and I haven't seen any seedlings.

The flowers aren't as showy as those of cardinal flower (L. cardinalis), partly because they're a violet blue but more because of all the leafy bracts interspersed with them on the stem. The hybrid L. x vedrariensis (a cross between L. siphilitica and L. cardinalis) has blue-violet flowers on a scape largely clean of bracts, like L. cardinalis, and I find it a lot showier. Know that some plants labeled L... read more


On Aug 8, 2016, Rockguy1 from Calgary,
Canada wrote:

They say it's short lived, but mine is five years old and still going strong. It's a ~2.5' tall clump with ~10 flower spikes covered with blooms, just starting to open up now. Bees love it. I haven't had any problems with invasiveness or self-sowing, but it's hemmed in by other plants on either side. I'll try to collect some seedlings this fall to grow elsewhere in my garden.


On Jun 22, 2014, kydrummer from Silver Spring, MD wrote:

Bought this for use at a farm because it had a tag in the pot "Deer won't eat this!". Deer in Maryland chop it down to stumps.


On Aug 8, 2013, wakingdream from Allentown, PA wrote:

Having grown this native plant by using one small seedpod found in a creek setting, I later returned to disperse more seeds to make up for my removal. I grew dozens easily in winter sowing jugs. The small Lobelia seedlings were robust enough to survive the separation after being tugged apart from the large clump inside the jug. They were eventually positioned on the shady, moist north side of my home, a match for the conditions in which I found the original plant. The shade of blue is captivating. Bloom time is August and September here in southeast PA. I noticed a vast number of seedlings appearing earlier this summer and will pot them up for gardening friends.


On Jun 18, 2013, plant_it from Valparaiso, IN wrote:

I can't wait to have the problem of too many seedlings b/c it spreads aggressively. Just getting to know this plant but its quickly becoming one of my favorites.


On Jan 4, 2012, tauberp from Aurora, IL wrote:

My favorite flower! Beautiful and very long blooming, with long flowering stalks. We have those in our front yard in front of yews and boxwoods and get a lot of compliments for those. Easy to grow and low maintenance, with mid summer to fall blooming period. Heavy clay soil and get not much water there, and it's north side with part shade, but doesn't stop it from thriving. We also have on the side of the house where it gets morning sun, and it is the most outstanding flowering plant we have. I love those deep blue flowers!


On May 31, 2010, EllaTiarella from Portage, MI (Zone 5b) wrote:

It's invasive in my garden; however, I do appreciate the late-season color. I bought one plant two years ago, it got ahead of me, and now it's "everywhere"! I think I have over 50 plants here and there in the 20 feet or so around the original. I plan to dig quite a bit of it out, and leave just a clump or two. My recommendation is to be on guard for seedlings, and be sure to dig them out right away where they are not wanted. Perhaps prompt deadheading would help.


On Dec 3, 2009, jmorth from Divernon, IL (Zone 5b) wrote:

Blooms late summer to fall here. It's a wildflower in Illinois, often found in wet ground, marshes, and fens. Mine grow quite peacefully in the garden with no special HOing consideration. These plants self-seed but mine haven't portrayed any invasive characteristics. Butterflies and hummers are attracted to their flowers and being a relatively late bloomer they can be a major attractant.
Reportedly native Indians (Mesquakies) finely chopped the roots and secretly mixed them into the food of a quarrelsome couple to rekindle love lost. Other tribes used it as a cure for syphilis (probably influencing the siphilitica part of the scientific name) and other ailments.
These plants self-seed but mine haven't portrayed any invasive characteristics. Butterflies and hummers ar... read more


On Sep 2, 2008, plantaholic186 from Winnetka, IL wrote:

I love this plant, but I warn others that given a wet location, it's an aggressive spreader. I planted one in a very wet area of my garden, and there are seedlings everywhere. They're all blooming, so at least there's that, and they are easy to pull out, so I thin them out periodically. I have some in a full sun, hot, dryish bed that does beautifully, but hasn't spread babies around. I absolutely love this plant though: a beautiful blue.


On Aug 16, 2007, dkm65 from Cedar Falls, IA (Zone 4b) wrote:

Intense blue flowers, on the violet side of the color. It mixes well with its sibling, cardinal flower (Lobelia cardinalis), with it similar bloom times and very intense, deep red flower. It doesn't draw hummingbirds like cardinal flower, but they do feed on it.

The plant file notes that it has above average water needs, but this isn't entirely accurate. As with many prairie natives, it can tolerate periods of drought, as it has very deep roots. It does best when it is in a low-lying spot, such as a swale or raingarden, with well-drained but occasionally flooded soil. Ours does fine going several weeks without any rain or watering once established.


On Feb 5, 2006, Gabrielle from (Zone 5a) wrote:

A very pretty, easy to grow plant. Other names include Lobelia syphilitica, Blue Cardinal Flower, Great Lobelia, High Belia. Light aids germination of seeds. Blooms in August - September in my garden.


On Jan 17, 2005, JodyC from Palmyra, IL (Zone 5b) wrote:

The flowers attract bumblebees primarily. Less common visitors include hummingbirds, butterflies, and Halictid bees. The latter group of bees collect pollen only and are non-pollinating. Most mammalian herbivores don't eat this plant because the foliage contains several toxic alkaloids, chief among them being lobeline and lobelanine. These toxic substances produce symptoms that resemble nicotine poisoning. However, it has been reported that deer occasionally eat this plant, perhaps enjoying greater immunity to these toxic substances than other animals. The seeds are too small to be of much value to birds.


On Oct 4, 2004, hanna1 from Castro Valley, CA (Zone 9a) wrote:

I bought mine in Spring at my favorite nursery in Oakland, I transplanted it in a new pot in semi-shade, got a lot of water, was beautifull, and very blue, I had never seen one before, new plantlets are growing at the base of the original and I can't wait to see it take off again.


On Sep 12, 2004, lego_brickster from Lawrenceville, PA (Zone 5b) wrote:

This is native in my zone 5 area. We found several stalks of it this year growing in the weeds around our pond. It's in full sun, but has very wet feet. It shares the same terrain as our cattails.

We're going to try collecting seeds this year. It would look great in a mass planting. Ours grow in very narrow spikes with little lateral foliage or stalks.

It must spread by seed, but only a little. We find small growths of it here and there in our field.


On Aug 22, 2004, karenbarnett from El Dorado, AR wrote:

Native to my area in southern Arkansas, this beauty thrives in intermittent stream beds, as well a in a pot on my sunny deck. Semi-shade deepens the intensity of the blue.


On Oct 10, 2003, flowerman from Saint Louis, MO wrote:

I have seen these grow on rock walls along river banks. They are spectacular and inspiring, to say the least!


On Sep 28, 2003, Karenn from Mount Prospect, IL (Zone 5a) wrote:

I really like this particular variety - it shuffles itself around the planting bed and parks where it is happiest! It is not invasive (like goose-neck loosestrife), just puts a clump or two around the bed. And blooms just when the summer bloomers are fading! What a great plant!


On Aug 7, 2003, Ladyfern from Jeffersonville, IN (Zone 6a) wrote:

Easy from seed--will even bloom a little the first year! Great for the butterflies and hummingbirds. The foliage is a handsome dark green. A group of these is just specatacular in the late summer garden.


On Aug 31, 2002, lupinelover from Grove City, OH (Zone 6a) wrote:

This plant is much easier to please than the better-known Scarlet Lobelia, so that most gardeners should be able to find a place for it in their landscape. It tolerates full shade, but blooms much better in full to partial sun.


On Mar 8, 2001, Terry from Murfreesboro, TN (Zone 7a) wrote:

Native to North America, produces spikes of blue flowers in late summer. The plant grows well in moist to wet soils and so is useful near water. The plant may be short-lived but will tend to reseed.