Leaves of Three, Leave It Be

As the holiday season comes into the home stretch and with a frosty morning last weekend, the two common local native vines are displaying holiday colors. Some, but not all, have changed from green to red.

Both creeper and poison ivy can be a bright cherry red during the waning days of autumn and early winter. With the seasonal change, it may be difficult to tell the two species apart.

Poison ivy (Toxicodendron radicans) and Virginia Creeper (Parthenocissus quinquefolia) both grow in the protected areas under the canopy of trees. Only poison ivy produces urushiol, a plant oil which will cause a severe skin rash when any part of the plant is touched.

The reds and purples in the leaves currently on display come from a pigment group called anthocyanins which reside in the cells. This chemical compound develops in the sap of the leaves.

Virginia creeper leaves are currently red, but so are poison ivy’s, and they are easy to confuse. The old saying “leaves of three, leave it be” is especially true in December as physically contacting poison ivy will still result in a rash and an itch.

These pigments are not present in the leaf during much of the growing season, but begin to be produced in August and September as the days become noticeably shorter. The amount and intensity of the reds and purples in leaves depends on a combination of environmental factors.

The breakdown of sugars in the sap, the intensity and duration of sunlight and the level at which phosphate declines in the leaf combine to produce a nearly infinite number of shade and hue possibilities.

The brightest colorations commonly occur when the fall days are bright and cool, and the nights are cold but not below freezing. Poison ivy and Virginia creeper often grow together and can be difficult to differentiate, but there is a critical trait which may help distinguish the two species.

In the case of poison ivy, an allergic reaction occurs by touching the plant, or by coming into contact with the oil on animals, tools, clothes, shoes, or other items which have struck the plant. Even the smoke from burning the plants contains oil particles which can be inhaled, causing lung and airway irritation.

Contact dermatitis is not a problem with Virginia creeper. While difficult to control, there are some horticultural uses for this plant.

Poison ivy and Virginia creeper both grow in heavy shady or sunny locations throughout the panhandle region and the rest of Florida. Each can produce a vine up to 150 feet long that climbs high on trees, walls, and fences or trails along the ground.

Both plants are common along old, unmanaged fence rows and the edges of paths and roadways. Only poison ivy contains urushiol, the skin irritant. This compound is present at all times of the year, even when bare of leaves and fruit in winter.

The leaf shape and the form of the leaf are one telling factor. Poison ivy always has three leaflets, and Virginia creeper usually, but not always, has five leaves at the end of a stem.

It is important to remember blackberries have three leaves on a cluster, but they do not turn red in the autumn. Also, blackberries have thorns on their vines.

The other easy identifier is the berries produced. Poison ivy’s are white, and Virginia creeper’s are purple to black.

Unless well acquainted with these vines, it is a good idea to avoid them all.