In our local area, these leaves have the most beautiful translucent golden yellow color in the autumn. The veins on the underside of the leaves are again armed with numerous spines. It is wise to avoid contact with this plant as the spines produce wounds that can easily become infected. If I remember correctly it has been established that Devil's Club is one of the plants that accumulate silicon in the spines which means that the wounds resemble those experienced from slivers of glass. Tweezers are a good addition to the day pack in Devil's Club country but it has been my experience that the spines break off easily at wound entry level.
Gloves are the best preventive medicine.
The flowers which bloom in June or July are not very showy or even very visible among the large leaves. They are small, whitish and numerous in compact heads arranged in pyramidal terminal clusters. The fruits are bright red, flattened, shiny berries in the now showy pyramidal terminal clusters. The fruits are not edible by humans but are relished by bears. One of my sources even lists the berries as toxic.