Of all the dozens of exotic plants imported into Sunshine State for specific purposes, few, if any, might have been ill-suited for its task than Australian pine.
On top of that, Australian pine has invaded hundreds of thousands of acres of precious conservation lands from Everglades National Park in Miami-Dade County north to the wilds of Flagler County, all of which makes its introduction here a fairly collosal environmental mistake.
Australian pine, or we should say Australian pines — there are really three different species rather than one — came to Florida in the 1890s. Someone had the bright idea that these tall, graceful trees would make the perfect windbreak along Florida’s beaches, canals, roadways and more.
Perfect, except for two rather important details: Australian pines have shallow root systems and can be easily overturned in high winds. Its wood is brittle and breaks under windy conditions. And remember, Florida is hurricane alley.
Before we go on, some basics are in order. As we just noted, there are three species of what we call Australian pine found in South Florida, all bearing close resemblance to each other and all three members of the genus Casuarina. Worldwide, there are 17 members of Casuarina, all native to eastern Africa, southern and southeast Asia, the Pacific and/or Australia, naturally.
Despite the name, they are not pines, nor are they closely related to pines.
The most common of the three found in the Sunshine State and the one shown in the photos on this page is C equisetifolia, commonly known as Australian pine or horsetail casuarina.
There is C glauca, commonly known as suckering Australian pine. The name provides a pretty good clue as to how to tell it apart from its cousins: suckering Australian pine produces suckers — new trees that grow off the roots of the parent tree.
The third is C cunninghamiana, commonly known as beefwood or river sheoak. It’s the least common, found only in a handful of South Florida’s parks and preserves, according to the Institute for Regional Conservation.
Note: when we refer to Australian pine, singular, we are referring to C equisetifolia; when we use Australian pines, plural, we are referring to the three species collectively.
The three species have different ranges but one or another can be found in most peninsular counties as far north as St. Johns and as far south as Monroe. Australian pines are only found in Florida among the 48 continguous states, but they’re also found in Hawaii.
Both Australian pine and suckering Australian pine are Category I invasives as determined by the organization formerly known as the Florida Exotic Pest Plant Council, now the Florida Invasive Species Council. Beefwood is classified as a Category II invasive, meaning it’s spreading in the wild, has the potential to damage ecosystems but hasn’t, yet.
While Australian pines might not be actual pines, they do look the part with what appears to be long, soft needles. But needles they’re not. Rather, they’re segmented and ridged branchlets, with whorls of tiny, scale-like leaves attached.
Count the number of leaves in the whorls and you can identify the species of Australian pine you’re looking at. Our guy, C equisetifolia, has six to eight; C glauca, suckering Australian pine, has 10 to 17; C cunninghamiana, aka beefwood, eight to 10.
Other features used to identify individual species include length and width of the branchlet segments, number of ridges and the presence or absense of dark bands at the base of the leaves.
But what about the cones? Australian pines have cones, don’t they? Nope. What appears to be cones are actually clusters of flowers, which give way to woody clusters of fruit filled with winged seeds. The trees bloom twice a year, in April and June, and produce proverbial tons of seeds later in the year.
Australian pines can be as tall as 150 feet, but are typically 70 to 100 feet, with an irregular crown. The bark is gray to reddish brown, smooth and peeling on younger trees, rough and furrowed on older ones.
As we said, these trees were brought to Florida in the 1890s to act as windbreaks along canals, beaches and roads. They were also used to prevent erosion along canals and beaches.
What’s the problem with these trees? Let’s count ‘em.
— As we noted earlier, Australian pines are brittle and easily break in high winds.
— They have dense, shallow root systems and are easily uprooted in high winds. They also don’t do much for erosion control. Australian pines growing along the banks of bodies of water can be undermined.
— Their dense roots do, however, prevent native vegetation from grow underneath the trees. Not only that, they can make it difficult to impossible for American crocodiles and sea turtles to dig their nests in soil and sand where they’re present.
— The dense litter of dead branchlets and seed pods that accumulate underneath Australian pines act as mulch of sorts, also blocking the growth of native plants.
— Australian pines produce allelopathic chemicals that prevent the seeds of other plant species from germinating.
— They reproduce like crazy and can take over a swath of land swiftly.
— There is a sort of domino effect in play. The plants that Australian pines block are often the same plants that species like marsh rabbits, gopher tortoises and many birds depend on for their survival. Take away these plants and you diminish these animals as well.
Along the Intracoastal Waterway and canals, property owners cut down native mangroves (that practice is now illegal) to improve the view or provide better access to the water. In many places these vital trees were replaced, either deliberately or accidentally by Australian pines. Where mangroves prevent erosion and flooding and provide shelter for young sealife, Australian pines don’t do anything. As a result, water quality suffered and stocks of fish declined.
And one more thing the pollen from Australian pines is highly allergenic.
Despite all this, these trees do have their fans. As Florida began eliminating Australian pines throughout the state, a group of Key West residents successfully petitioned to save a grove of the trees that line the beach at Fort Zachary Taylor State Park.
A two-mile stretch of A1A through the town of Gulfstream in Palm Beach County is lined with Australian Pines planted in the 1920s has been declared a state landmark, the trees protected not only from the chainsaw but from the actions of neighboring homeowners that might damage them.
Similarly, a recent online petition to stop Delray Beach from redeveloping Atlantic Dunes Park specifically mentioned preserving the Australian pines that shield it from the flow of traffic along A1A. The trees have a right to life, the petitioner said.
Other common names for these trees include ironwood and horsetail tree. All Australian pines are members of Casuarinaceae, the Australian pine family.