​Lonesome Historic Site


2006 TN-96  •  Burns, TN 37029  •  206-953-2766

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Science Station 12: Poisonous Plants

The main culprits are poison ivy, poison oak and poison sumac. The oil in these plants, called urushiol, is what causes a reaction when you touch it. You may have heard the saying “leaves of three, let it be.” That’s because poison ivy typically has three broad leaves. The plant can grow as a ground cover or as a thick, hairy vine on trees. Poison oak grows as a vine or shrub, and typically has leaves in clusters of three, but it can have up to seven leaves in a group. Poison oak leaves look very much like oak leaves. Poison sumac is much less common in Tennessee than poison ivy or poison oak. It looks like a small tree (or shrub) and grows most often in wet, wooded areas, like creek banks. The plants can grow as high as 15 feet and their leaves have smooth edges and pointed tips that grow in groups of seven to 13 per stem. All of these poisonous plants are present at Lonesome. Beware!