The Australian pine tree (Casuarina exisetifolia) is an exotic and extremely invasive tree that is fairly common on Sanibel and throughout southwest Florida. Although not part of the natural flora on the island, this upland tree is either loved, hated, or sometimes both by residents and visitors.  

While driving across the causeway to Sanibel, take notice of the tree line across the island. You will notice that most of the trees are around the same height. These are primarily the native trees that have adapted, due to tropical storms and hurricanes, to attain around the same height to minimize wind effects through safety in groupings. 

The individual trees that rise above that tree line tend to be the non-native examples such as Australian pines and Norfolk pines (Araucaria heterophylla) which are highly exposed and often take on the full force of winds during a storm. 

“Groupings of trees fair better than individual trees during tropical storms,” said SCCF Wildlife & Habitat Management Director Chris Lechowicz. “Large, heavy, and shallow-rooted exotic trees such as the Australian pines tend to fall over with high winds and can cause a lot of damage to buildings, yards, and obstruct roadways.” 

As a habitat management practice, Australian pines are removed or killed in place on conservation lands to prevent their spread across the island. In areas where they occur, the leaves (needles) they drop form a dense layer (duff) that suffocates the ground by preventing native ground cover plants to grow. 

“This is detrimental to uplands where gopher tortoises live because they shade out the ground and prevent grasses from growing which are essential to this keystone species,” said Lechowicz. 

Often, small numbers of Australian pines are left in place on conservation lands, after they have been treated with herbicide, to allow the nesting of several types of birds including raptors. This is only implemented in areas where there will be no damage to human structures if they fall.

Although some private landowners like them because they provide shade on their properties, they are usually unaware of the negative and often expensive repercussions that could occur if they are left to grow to full size. Cutting down and disposing of a single tree can cost thousands of dollars with the removal or grinding of the stump costing extra. 

Some people hire a company to simply “top the tree” after several years which involves cutting the upper part of the tree off, so it doesn’t grow over their home. This is a cheaper option but will need to be repeated several years later if the tree is not treated with herbicide in place. Also, be aware that the wood of Australian pine becomes very hard (almost stone-like) after it is cut and left on the ground after a short amount of time. After it is in this state even chainsaws have a hard time cutting through it.

“It is highly recommended that any young trees be removed or treated in place from private properties before they get too tall and expensive to deal with,” Lechowicz adds.