Alligator Flag (Thalia geniculata)

Also known as: fireflag

Quick Facts

• Type: wildflower
• Size: 4-8 ft tall
• Sun: full
• Water: high
• Soil: Shallow water or very wet soil
• USDA zones: 8-11

Towering purple flower spikes rise above big paddle-shaped leaves in summer ponds.

A bold architectural plant for water gardens; needs its feet wet year-round.

In the Landscape

Best suited to wetland restoration, retention-pond edges, bog gardens, and rain gardens. It's too bold for small water features — it needs standing water or saturated soil and room to reach its full 6–9 feet.

Care & Propagation

Plant in full sun to part shade in consistently wet soil or shallow standing water, and never let it dry out. It dies back to the ground in winter and returns each spring, needing little more than removing dead foliage. Give it space — mature clumps are enormous.

Sow seeds in warm, wet soil in spring, or divide the rhizomes during the dormant season in late fall or winter, making sure each piece has healthy roots and a growing shoot.

Wildlife Value

It is the documented host plant of the Brazilian skipper butterfly (Calpodes ethlius), and its tall foliage provides cover for nesting water birds.

🌱 Fun fact: Alligatorflag belongs to the arrowroot family, Marantaceae — the same plant family that gives us arrowroot starch.

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🌴 In Florida

A bold architectural plant for water gardens; needs its feet wet year-round.

🌿 Keep exploring

More Florida natives worth meeting:

• American White Waterlily (Nymphaea odorata)
• Anisescented Goldenrod (Solidago odora)
• Apalachicola Wild Indigo (Baptisia megacarpa)