In some locations, you need to watch out, because forsythia is considered invasive—but not for the reasons you might be expecting. The problem is not that forsythia seeds like crazy. In fact, you can plant varieties that do not go to seed at all. The issue is the “stoloniferous” nature of the plant. Basically, sometimes the branches of this plant can drape down to the soil. With most plants, this wouldn’t be an issue, but with stoloniferous plants, it is, because they can root right on the spot. Before you know it, you have an additional forsythia growing right next to the first. The Highlands Current notes, “Forsythia doesn’t appear on the U.S. Department of Agriculture’s list of invasive plants, although the characteristics … are similar to some other invasive plants. It doesn’t colonize and crowd out native plants like Japanese barberry or Euonymus (burning bush) do. These plants escape from their original site and can spread quickly and easily.” Note, however, that sometimes it may be difficult to get other plants to thrive close to your forsythias. If you are concerned about forsythia plants behaving invasively in your yard, you may want to plant them in containers. Remember, however, you still need to be concerned about branches going to root if they reach the ground nearby. So, forsythias might be better off placed on a patio where they are some distance from your garden beds.