Jacksonville Arboretum & Gardens 1445 Millcoe Road, Jacksonville, FL 32225  

Photo: Chuck Hubbuch

The oak genus is comprised of approximately three hundred to six hundred species. The difference between the two numbers is large. As sometimes happens in large plant genera, some botanists want to lump related plants together while others want to split them apart into separate species.

Oaks are especially common in forests of the Northern Hemisphere but are native to every continent except Australia and Antarctica. With so many species scattered over such a wide range, the different species of oaks vary in appearance quite a bit. They range from shrubby species that spread by underground rhizomes to forest giants. One thing that they all have in common is the acorn. This is a seed with a hard coat that is partially covered by a cup of small bracts.

Some of the larger oaks are prized around the world for their timber. Oak wood is durable, resists warping and finishes well. It has been used for building boats, furniture, homes and larger buildings. Oak is also used for building barrels and lends a distinctive flavor to aging wine, brandy and whiskey. Oak wood makes an excellent fire wood, too.

Tannin from oak bark has been used to tan leather and used as a rust inhibitor on steel. Tannins from oak gals have been used to make ink. Today, synthetic tannins are used more often than tannins from plants.

The cork in your bulletin board or wine bottle comes from an oak. Specifically, cork comes from the bark of the cork oak, Quercus suber. Damaging too much of the bark off a tree can kill it. So, cork is removed from the tree in vertical strips in a way that allows the tree to recover between harvests. In this way, a cork oak can be harvested several times during the life of the tree.

Acorns are edible. They tend to taste bitter because of the tannins they contain. Types with low amounts of tannin may be eaten after roasting. Native Americans made acorns edible by grinding the seeds into a flour and then washing the flour repeatedly to remove the tannins. The flour was then cooked to make cakes or breads. Acorns are important wildlife food, too.

In Florida, where oaks are abundant, their flowers drop large amounts of pollen in spring and can irritate our eyes and sinuses for a few weeks each year. Medical doctors and the makers of allergy medications must love oaks. Regardless, live oak makes a beautiful tree and is one of the most commonly planted landscape trees in the southeastern United States.

Fourteen species of oak are native to Florida. The different species grow from low swamps to the high, dry ridges. Oak trees can be seen throughout the Jacksonville Arboretum and Gardens. Live oak, laurel oak, water oak, turkey oak, and myrtle oak are the common species along the trails.

By Chuck Hubbuch