Casuarina spp.: Australian-Pine1
Long-favored for use in erosion control along beaches, Australian-pine tree is now outlawed in many parts of Florida due to its invasive nature, rapid growth rate, and non-native status. It is not a true pine tree and is not related to the pines. A straight, upright tree capable of reaching 70 to 90 feet in height and possessing rough, fissured, dark gray bark, Australian-pine has what appear to be long, soft, gray green needles but these "needles" are actually multi-jointed branchlets, the true leaves being rather inconspicuous. These "needles" sway gently in the breeze and give off a distinctive, soft whistle when winds are particularly strong. The insignificant flowers are followed by small, spiny cones, less than ½-inch-long.
Scientific name: Casuarina spp.
Pronunciation: kass-yoo-ar-EYE-nuh species
Common name(s): Australian-pine, casuarina
USDA hardiness zones: 9B through 11 (Figure 2)
Origin: native to Australia, Southeast Asia, and the Pacific Islands
UF/IFAS Invasive Assessment Status: prohibited from use in Florida according to the Federal Noxious Weed List, the Florida Department of Agriculture and Consumer Services (FDACS) 5B-64.011 Prohibited Aquatic Plants, or FDACS 5B-57.007 Noxious Weed List (North, Central, South)
Height: 70 to 90 feet
Spread: 30 to 40 feet
Crown uniformity: irregular
Crown shape: upright/erect
Crown density: open
Growth rate: fast
Leaf arrangement: whorled
Leaf type: simple
Leaf margin: entire
Leaf shape: scale-like
Leaf venation: unknown
Leaf type and persistence: evergreen
Leaf blade length: < 2 inches
Leaf color: gray green
Fall color: no color change
Fall characteristic: not showy
Flower color: yellow
Flower characteristics: not showy; male—emerges on spikes at the end of the needle-like structure; female—emerges in clusters from leaf axils
Flowering: year-round but most abundant in the spring, and then again in late summer/early fall
Fruit shape: round, oval; cone-like
Fruit length: < ½ inch
Fruit covering: dry or hard; spiny
Fruit color: brown
Fruit characteristics: does not attract wildlife; not showy; fruit/leaves a litter problem
Fruiting: year-round but most abundant in early summer, and then again in mid winter
Trunk and Branches
Trunk/branches: branches droop; not showy; typically one trunk; no thorns
Bark: dark gray, fissured, and rough
Pruning requirement: needed for strong structure
Breakage: susceptible to breakage
Current year twig color: green
Current year twig thickness: thin, medium
Wood specific gravity: unknown
Light requirement: full sun to partial shade
Soil tolerances: clay; sand; loam; alkaline; acidic; well-drained to occasionally wet
Drought tolerance: high
Aerosol salt tolerance: high
Roots: can form large surface roots
Winter interest: no
Outstanding tree: no
Ozone sensitivity: unknown
Verticillium wilt susceptibility: unknown
Pest resistance: resistant to pests/diseases
Use and Management
Highly salt- and drought-tolerant, Australian-pine was widely used in seaside landscapes as a windbreak, screen, clipped hedge, and for topiary. Its ability to withstand heat and other adverse conditions made Australian-pine a favorite for street tree or specimen use also. It is not planted now due to the problems it has created including the elimination of habitat for native plants. Injured trees compartmentalize wounds poorly and decay advances rapidly through the trunk. Old trees which have been topped and abused often become hazardous and they can fall over or drop large limbs.
Growing in full sun or partial shade, Australian-pine will tolerate many adverse conditions, dry or wet soil, heat or high winds. Trees are hardy to about 25°F. Vigorous sprouts often originate from the roots of older trees knocked back by the cold.
No pests are of major concern.
Koeser, A. K., Hasing, G., Friedman, M. H., and Irving, R. B. 2015. Trees: North & Central Florida. Gainesville: University of Florida Institute of Food and Agricultural Sciences.
Koeser, A.K., Friedman, M.H., Hasing, G., Finley, H., Schelb, J. 2017. Trees: South Florida and the Keys. Gainesville: University of Florida Institute of Food and Agricultural Sciences.