1. English ivy (Hedera helix) is a non-native species to the US that originated in Europe. It invades forest edges and trees by climbing to their tops and blocking sunlight, weakening the trees. 2. English ivy was introduced to the US in 1727 and has spread throughout eastern and western states. It thrives in shady and sunny areas but cannot tolerate drought or salinity. 3. English ivy is an aggressive invader that threatens all levels of vegetation in forests and open areas by growing along the ground and into tree canopies. It has become a serious weed despite continuing to be sold as an ornamental plant.