Perennial
Alligator Flag
Thalia geniculata
Varieties We Carry
StandardThalia geniculata
Sizes & Pricing
1 galFrom$7.95
Fresh this week. Last restocked Mar 9.
LightFull Sun, Part Sun
WaterHigh
Mature size6-10 feet × 4-6 feet
About Alligator Flag
Alligator Flag (Thalia geniculata) is a tall, native aquatic or marginal perennial found in marshes and freshwater wetlands from Florida through tropical America, with large, canna-like leaves and slender stems bearing small violet flowers. It is an important native wetland plant providing habitat and visual drama in water gardens and pond edges. Starting at $7.95.
Plant details
- Bloom Season
- Summer, Fall
- Flower Color
- Purple
- Growth Rate
- Fast
- Foliage
- Deciduous
- Soil
- Loam, Acidic, Wet
Best planting months
Recommended forZone 9b · St. Augustine, FL
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F
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JNow
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This monthGood windowOther months
Seasonal care
New foliage emerges. Good planting window.
Bloom season. Higher water demand in summer heat.
Bloom season. Foliage may begin to change or drop. Ideal planting window.
Dormant — drops foliage.
Care essentials
Light
Grow Alligator Flag in full sun to part sun; it thrives alongside ponds, ditches, and rain gardens throughout Northeast Florida and performs best with maximum sun exposure in standing or saturated water.
Water
Alligator Flag is an aquatic or marginal wetland plant requiring consistently wet to flooded conditions; it grows naturally in swamps and freshwater marshes and should never be allowed to dry out.
Soil & Fertilizer
Plant in loamy, moist to wet, slightly acidic soil or directly in shallow water up to 12 inches deep. No fertilizer is needed in natural settings; in managed water gardens, a light slow-release aquatic fertilizer can be added in spring.
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Common questions
Is Alligator Flag a good plant for St. Augustine?
Alligator Flag is a perennial for Zone 9b coastal Florida gardens, reaching 6-10 feet × 4-6 feet.
Care information verified from
Last reviewed February 2026. Our care guidance comes from trusted horticulture sources and decades of helping St. Augustine gardeners. Conditions here can vary dramatically from one area to the next, so come ask us and we'll tailor it to your yard.