Swamp Oak / Longleaf Ironwood (Casuarina glauca): The Salt-Tolerant She-Oak

Swamp Oak (Casuarina glauca), also called Saltmarsh, Longleaf Ironwood, or Gray She-Oak, is a tough, fast-growing Australian tree uniquely adapted to waterlogged, saline soils. Its needle-like branchlets and nitrogen-fixing ability make it a restoration superstar for coastal wetlands.

Distinctive Form

Not a true oak—Casuarinas are in their own family. The "needles" are actually photosynthetic branchlets (cladodes); true leaves are tiny teeth at nodes. This gives a fine, conifer-like texture. The tree reaches 40–60 feet with a narrow, pyramidal crown. Bark is rough, fissured, gray-brown. Separate male (orange spikes) and female (round cones) flowers on the same tree.

Taxonomy

• Family: Casuarinaceae
• Genus: Casuarina
• Species: glauca

Ecological & Practical Uses

Thrives in brackish swamps, salt marshes, and estuaries where few trees survive. Fixes nitrogen via Frankia bacteria in root nodules. Used for land reclamation, windbreaks, and erosion control in coastal tropics/subtropics. Wood is extremely hard, dense, and durable—prized for flooring and fuel. Invasive in Florida; plant responsibly.