Question: How can I eliminate the briars with glossy green leaves?

Answer: If you have virgin ground that is infested with this smilax briar you can get rid of most of it simply by mowing it to the ground. Probably less than 5 percent will return from the roots. There are no really effective herbicides for smilax since it has so few leaves and comparatively extensive root systems. If you have plants that sprout back again you'll probably find it easiest simply to dig the root systems out, tubers and all, with a sharpshooter spade. It will take only a minute or two per plant.