Weeds reduce the aesthetic qualities of landscape plantings and compete with nursery crops for nutrients, water, and light. Root systems compete for nitrogen and water. Even seemingly non-competitive weeds like bittercress (Cardamine spp.) have been shown to reduce growth of container-grown plants. Tall weeds and vines shade crops, reducing photosynthesis and growth. Vining weeds such as morningglory (Ipomoea spp.) are particularly damaging because they disfigure stems and new growth. In landscape plantings, weeds must be controlled or removed to maintain quality aesthetics. Weeds may also need to be removed for health and safety reasons
Preemergence herbicide efficacy summary chart, Ranking the efficacy of preemergence herbicides on most weeds of nursery and landscape plantings.