5. English Ivy (Hedera helix)
Considered an invasive species in many parts of the United States, English ivy has even been outright banned in the state of Oregon. While its clinging vines make for an excellent ground cover or building façade green, using it anywhere else in the backyard can be problematic at the least. Very difficult to control once it’s established, it spreads so densely that it can choke out other plants and create an “ivy desert” effect, while its penchant for climbing can cause young trees to topple over from its creeping weight.
6. Mint (Mentha spp.)
Despite their culinary uses and air freshening aroma, many varieties of mint – including peppermint, spearmint, and catmint – are prolific growers. Utilizing their twofold spreading technique, mint plants are able to conquer far and wide via underground rhizomes and horizontal runners. They can quickly take over new terrain so it’s best to grow them in containers and to harvest their leaves frequently to keep them at bay.