Casuarina equisetifolia – Common Ironwood
Scientific Name: Casuarina equisetifolia
Synonym: Casuarina litorea
Common Names: Common Ironwood, Beach Sheoak, Horsetail Casuarina, Australian Pine, Australian Beefwood
Duration: Perennial, Evergreen
Growth Habit: Tree
Hawaii Native Status: Introduced. This naturalized forestry tree is native to Australia.
Flower Color: Inconspicuous (light brown)
Flowering Season: Spring
Height: Up to 100 feet (30 m) tall, but usually less
Description: These trees are monoecious. The male and female flowers are light brown and inconspicuously tiny. The male flowers are at the tips of the leaf twigs, while the female flowers are on the branchlets below the leaf twigs. The female flowers are followed by rounded, 1/2 to 3/4 inch (1.3 to 1.9 cm) wide, hard, warty, brown, pinecone-like fruits. The seeds are winged samaras.
The tiny, scale-like leaves are in whorls of 6 to 8 around the green, 9 to 15 inch (23 to 38 cm) long, 1/32 inch (1 mm) wide, pine needle-like leaf twigs. The leaf twigs are jointed like those of a Horsetail (Equisetum spp.). The dead, brown, fallen leaf twigs litter the ground under the trees like pine needles. The branches are slender and drooping, and the trees have a wispy appearance. The bark on older trees is rough, gray brown, and flaking on the exterior and beefy red brown on the interior.
This non-native, allelopathic tree is extremely weedy and invasive, especially along the coast, so it should never be planted and should be removed if possible. The wood makes good firewood.
Despite its similarity to a pine tree or tamarisk, this species is neither and is completely unrelated. This is the most common and widespread Casuarina species found here in Hawaii. The similar River Sheoak (Casuarina cunninghamiana) is typically only a cultivated tree here and has shorter, slightly thinner leaf twigs and smaller fruits, while Gray Sheoak (Casuarina glauca) has longer, thicker leaf twigs, young leaf twigs that are curved at the tip, and smaller fruits.
Kingdom: Plantae – Plants
Subkingdom: Tracheobionta – Vascular plants
Superdivision: Spermatophyta – Seed plants
Division: Magnoliophyta – Flowering plants
Class: Magnoliopsida – Dicotyledons
Family: Casuarinaceae – She-oak family
Genus: Casuarina Rumph. ex L. – sheoak
Species: Casuarina equisetifolia L. – beach sheoak
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