LEAVES OF THREE–LEAVE IT BE!

poison_ivyby Larry Williams, UF/IFAS Extension Agent

You have probably heard “leaves of three, leave it be” since childhood. This old rhyme refers to a couple of poisonous plants frequently found in Florida – poison ivy and poison oak.

Identifying poisonous plants is the first step in avoiding allergic reactions. The saying “leaves of three, leave it be” is a good rule of thumb. Poison ivy and poison oak have leaves with three leaflets.

Poison ivy has many forms and can be confused with other plants. It is usually a woody shrub or vine. It can grow vertically on trees, walls and fences or horizontally along paths. Although the shape of leaves can vary, even on the same plant, the typical leaf consists of three leaflets on a long stalk. Poison ivy produces white, waxy berries.

Poison oak is most frequently found as a low growing shrub. It does not usually grow as a vine. Leaves are similar to poison ivy but the leaflets are lobed, resembling lobed leaves of some oaks.

Poison sumac grows as a woody shrub or small tree. It usually grows 5 to 6 feet in height but may reach 25 feet. A poison sumac leaf consists of seven to 13 leaflets, which are three to four inches long and one to two inches wide. Leaflets are arranged in pairs with a single leaflet at the terminal end of the leaf. This plant turns bright red-orange in color during fall. It is found most commonly in swamps and bogs.

Poison oak and ivy can be found in landscape beds and wooded areas. Repeatedly cutting back the plant to the ground will eventually eradicate the problem.

Herbicides containing the active ingredient glyphosate can also be used. This systemic product is translocated throughout the leaves, stems and roots when applied to the foliage. Repeated sprays may be required. Other herbicides that can be used to control these poisonous plants are often called “brush killers” and contain the active ingredient triclopyr. Regardless of the herbicide chosen, be sure to follow label directions carefully.

Poison ivy vines growing up trees require a different approach. Cut the vines two to three feet from the ground. Several weeks later, after the base of the vine has regrown, spray it with a glyphosate herbicide. Repeat the spray each time new growth is seen. Several applications may be needed to control mature plants.

Be very careful about contact with these plants as all parts potentially can cause an allergic reaction.

The following UF/IFAS Extension link has more information on these plants. http://edis.ifas.ufl.edu/pdffiles/EP/EP22000.pdf

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