Alligator Flag, Fire Flag, Red Stemmed Thalia

Thalia geniculata

Family: Marantaceae
Genus: Thalia (THAL-ee-uh) (Info)
Species: geniculata (gen-ik-yoo-LAH-tuh) (Info)


Ponds and Aquatics

Foliage Color:


Bloom Characteristics:

Unknown - Tell us

Water Requirements:

Very high moisture needs; suitable for bogs and water gardens

Where to Grow:

Unknown - Tell us


8-10 ft. (2.4-3 m)


24-36 in. (60-90 cm)


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)

USDA Zone 10a: to -1.1 C (30 F)

USDA Zone 10b: to 1.7 C (35 F)

Sun Exposure:

Sun to Partial Shade


Unknown - Tell us

Bloom Color:


Bloom Time:

Late Spring/Early Summer

Mid Summer

Late Summer/Early Fall


Grown for foliage


Other details:

Unknown - Tell us

Soil pH requirements:

Unknown - Tell us

Patent Information:


Propagation Methods:

By dividing rhizomes, tubers, corms or bulbs (including offsets)

From seed; stratify if sowing indoors

Seed Collecting:

Allow seedheads to dry on plants; remove and collect seeds


This plant has been said to grow in the following regions:

Anniston, Alabama

Phenix City, Alabama

Boca Raton, Florida

Clearwater, Florida

Clermont, Florida

Jacksonville, Florida

Melbourne, Florida

Okeechobee, Florida

Oldsmar, Florida

Port Saint Lucie, Florida

Punta Gorda, Florida

Venus, Florida

Savannah, Georgia

Spotswood, New Jersey

Ronkonkoma, New York

Georgetown, Texas

Kemah, Texas

La Vernia, Texas

show all

Gardeners' Notes:


On Apr 6, 2015, greenthum3 from Jacksonville, FL wrote:

I bought a baby plant about 6 inches tall years ago. I now have 4 large planters full of this awesome plant. Very fast growth, bright red stems.Dies back every winter and comes back, very easy to propagate from splitting. I haven't repotted in several years and it hasn't complained. I live in zone 9b


On Sep 26, 2010, yogadoga from Ronkonkoma, NY wrote:

this is my first season with this plant in my koi pond. I purchased this as a single baby plant on ebay . within a month it had grown dramatically to the point that I had to transfer to a 5 gallon container. according to the information I've read it grows to 6ft height, my plant is well over 8 ft high she is in stones only, no soil and in around 3 inches of water.
I live in long island , ny.

my concern is how do I winter her? do I have to cut her down in order to put her at bottom of pond? she is way too big to store inside.


On Jun 1, 2010, LuvMyGreen from Clearwater, FL wrote:

i love this plant! its foliage is beatiful. very hardy and quick growing. i have mine in a pot and it sucks up water like crazy! seems to do best in half sun and half shade but see it in every type of light in the wild here in clearwater. awesome plant though. happy gardening


On Mar 23, 2007, joshz8a from z8a, AL (Zone 8a) wrote:

Last year planted this from a 6" pot into a 20" pot, and it grew so well I'll be repotting this spring into at least a 24" pot. Beautiful sturdy leaves the main attraction but enjoyed the delightful tiny flowers. Although I'd read it was a bog plant, I just gave it daily waterings in summer, weekly in winter, as with all my other containers and it did fine in full sun. josh


On Jul 9, 2003, wanda11 from Baton Rouge, LA wrote:

This plant has been very successful in my garden which is located in Zone 8b. It started out last year as a small potted plant in one of my ponds, then I moved it and planted it in the ground. This year, the original plant is larger and we have a large number of new plants that sprouted from the seeds that dropped last year.


On Sep 25, 2001, Terry from Murfreesboro, TN (Zone 7a) wrote:

Thalia geniculata is slightly less hardy than T. dealbata. Its common name, Alligator Flag, may be the result of where the plant is found in its natural habitat, which is near the deeper water of the cypress swamps, where alligators are likely to be found.

Plant in shallow pond or in bogs where the soil will stay moist. It is reliably hardy to zone 8, but with mulching may survive winters outdoors as far north as zone 6. For best results, overwinter in a protected spot.


On Sep 24, 2001, Floridian from Lutz, FL (Zone 9b) wrote:

Alligator flag is a large broad leafed aquatic plant with small, delicate purple flowers. The bisexual flowers have 3 petals, 3 small sepals and hang in pairs on zigzag stems.
Its natural habitat is the freshwater wetlands of Florida and the West Indies. It blooms from around May through November.