Roundleaf Greenbriar (Smilax rotundifolia) forms thick stands in woodland areas and can invade wetlands. Native to southeastern United States, it is an invasive pest to northeast regions. The plant’s leaves are dark green and shiny. Small whitish-green 5-petal flowers form clusters that appear in May. These flowers are not showy but have an extremely long bloom time. Fruit color is a showy reddish-black to purplish-black. The plant is widely sold as an ornamental. Hand pulling can, with care, work to eradicate it locally, especially when there is a small number of vines. This form of removal creates patches of disturbed soil into which other plants will move.

The leaves of roundleaf greenbriar have a waxy look that is quite glossy. They grow along a thorny vine, turning yellow in the fall. Notice the tendril wrapped around an older vine in the upper left center of the photo.

These thorns, alternating around the stem, are quite pronounced.

Roundleaf greenbriar can form dense, impenetrable patches either following the ground profile or using its tendrils to climb up other plants.

Roundleaf greenbriar is known by other names: Common greenbriar, Common catbriar, Bullbriar, Horsebriar. Once established in an area, it forms dense thickets.