Invasive Species Spotlight: Australian Pine

Beach erosion, property damage, and habitat destruction, oh my! 

The Australian pine is still loved by many Floridians, but it's destroying native areas and causing widespread property damage.

Australian pine silhouetted against the sky

It may look like just another pine tree at first glance, but don’t be fooled! Common names can be deceiving, and the Australian pine (Casuarina equisetifolia) isn’t a pine tree at all. Its small, evergreen leaves lay flat against long trailing stems, and from a distance these multi-leafed stems look like pine needles. Its reproductive structures even resemble pine cones, but this tree is much more closely related to many broad-leaf trees than it is to the true conifers. Sadly, the deception doesn’t stop there. Early Floridians were also deceived into thinking the Australian pine was both useful and harmless, but this species is now one of the most damaging invasive plants in the country.

Needle-like branchlets of Australian pine

When Australian pine was first planted as a windbreak and shade tree along coastal areas and beaches, Floridians rejoiced! In the late 1800s, the species was seen as a godsend by Florida residents hoping to lessen the effects of hurricane winds on their coastal properties. Reaching up to 100 feet in height, with wide-spreading canopies and thick foliage, these handsome trees still provide shade for miles of beaches and coastal recreation areas in Florida. 

Sadly, by the early 1900s, it was clear that this species wasn’t the blessing it originally seemed to be. As the trees grew taller, they began to fall over in windstorms due to their shallow, wide root structure. Residents began to realize that although Australian pines do block some wind, they cause more damage than they prevent in windy conditions by falling across roads, houses and power lines. When they do fall, these trees are difficult to cut up and move due to their very dense and heavy wood.

Australian pines have fissured, grayish bark.

Australian pine branchlets sprouting directly from the root

Not only did Australian pines not fulfill their intended role, but they also spread quickly and began to cause damage to some of Florida’s most delicate ecosystems. These trees can produce thousands of fertile seeds a year in their cone-like reproductive structures, which are widely dispersed both by the wind and by wildlife like birds and squirrels. They also re-sprout quickly from the root when damaged, making them hardy and difficult to remove. Australian pine trees blanket the ground with their needle-like leaves, which form a thick layer that kills native groundcover plants and discourages seed germination. If you look through a thick forest of Australian pine you’ll notice little to no undergrowth, and these bare understory areas are horrible for native wildlife species that depend on low-growing native plants for food and shelter. When they spread through dune and beach areas, these trees shade out and kill deep-rooted beach plants that hold the sand together, often causing significant beach erosion. 

Thick blanket of old "needles" preventing undergowth

Because of its fast rate of spread and the serious damage that it does to Florida’s coastal ecosystems, Australian pine is now a category I invasive plant on the Florida Exotic Pest Plant Control Council (FLEPPC) list of invasive species. Category I invasive plants are those that have been shown to change native communities by displacing native species, changing community structures (e.g. turning grassland into forest), changing ecological functions (e.g. drying out wetlands or making an area less likely to burn in a wildfire), or hybridizing with native plants. Unlike many other invasive plants, Australian pine is additionally classified as a noxious weed in Florida, meaning that it is illegal to buy, sell, or possess.

These trees aren’t just impacting native plant communities; they also pose a threat to some of our sensitive wildlife. Since they spread so widely and grow along many of Florida’s beaches, Australian pine trees have also impacted our already declining sea turtle populations. Their wide-growing and shallow root systems honeycomb the sand in some areas, making it difficult for sea turtles to dig their nests properly. American crocodiles in southern Florida are similarly affected when their nesting sites are colonized by Australian pines. 

Shallow Australian pine roots breaking the surface

Because they cause serious harm to Florida’s native plant and animal communities, damage our beaches by encouraging erosion, and pose a serious risk to roads, power lines, and homes, these trees should be removed whenever possible. If you have Australian pines on your property, it’s never too late to get rid of them and replace them with deep-rooted native trees which are more likely to withstand storm winds.

Lots of Floridians have an attachment to these beautiful and widespread trees, and it can be hard to part with them and the shade they provide, but we have to keep the health of our beaches, native plant communities, and wildlife in mind—not to mention our roofs, roads, and electrical grid! 

For more information about Australian pines, visit the University of Florida Institute for Food and Agricultural Science (IFAS) species page or take a look at the FLEPPC Australian pine management plan. For more information about invasive plants in general, visit the IFAS invasive plants page.