Poison ivy typically has leaves composed of three leaflets, which is why the common saying goes, "leaves of three, let it be." Each compound leaf consists of three leaflets: the middle leaflet has a longer stalk, while the two side leaflets have very short or almost no stalks and are directly opposite each other on the stem

. However, research has found that poison ivy plants can sometimes have more than three leaflets, including five-leaflet forms in different orientations (pinnate and palmate), though this is less common and adds complexity to identification

. Despite this variability, the classic identification feature remains the three-leaflet arrangement. In summary:

• Most poison ivy leaves have three leaflets per leaf.
• Occasionally, poison ivy may have five leaflets, but this is not the norm.
• The three leaflets are arranged with the middle leaflet on a longer stalk and the two side leaflets directly opposite each other with short stalks

Therefore, the standard and most reliable characteristic is that poison ivy leaves have three leaflets.