Knotweed by the creek

Getting rid of this small patch of knotweed is very important, to keep it from becoming a much bigger problem.  

Can you distinguish the jewelweed (a native plant) from the knotweed in the picture above?  The jewelweed is on the lower right; the leaves have undulations on the edges, unlike knotweed.  We think that in past weed control efforts, jewelweed was sometimes killed along with the knotweed. Now we make sure that volunteers can tell the difference.

Leaving knotweed by the creek

Sometimes people wonder why we aren't controlling all the invasive plants on the trail, like knotweed for example.  Effectively managing invasive species in large areas involves a lot more than  just trying to kill them off, and many natural area managers are struggling to find effective strategies.  Many of the more common knotweed removal strategies (like smothering, using herbicide, or digging) kill all the plants, not just the knotweed.  Then guess what grows back? The fastest growing, most invasive species in the area.  This makes the problem worse than it was before.  There are areas along the trail where failed attempts to control knotweed and other invasive species have made the situation worse rather than better.  

Along the creek, we have a second important consideration.  Knotweed does hold the soil along the bank.  We would rather have native shrubs doing this job, but knotweed is far better than nothing at all. Even natural lands groups realize that knotweed is here to stay; the Knotweed Floodplain Thicket is recognized as a wetland plant community by the Pennsylvania Department of Conservation and Natural Resources.  So especially near the creek, we need a knotweed control strategy that does not result in bare soil. 

You can read more about our strategies for invasive species on other pages in this site. We subscribe to the Bradley Method, which was developed in Australia to restore bush vegetation.  It works with nature, not against it as many other methods do. The Bradley Method keeps the soil covered at all times, which is important in stormwater management and in sequestering carbon dioxide, a greenhouse gas.  It also preserves animal habitat and food sources. 

The  basic idea is to work in from the edges of a large knotweed infestation to slowly allow better plants to surround it. We cut knotweed but leave the desirable plants, like jewelweed and raspberry, so they can eventually dominate and begin a natural succession process. In some areas where many of the desirable native plants have been destroyed we add seeds and sometimes plugs of plants to eventually compete with the knotweed, We also focus on trying to prevent future problems by removing knotweed where it is just starting, like in the picture to the left. 

One of the biggest challenges in knotweed control is what to do with the stems after they are cut. Even a small piece of stem can regenerate a whole new knotweed colony.  This is one reason that weed-whacking and digging up plants cause problems--little bits are left behind and can regrow, or, even worse, get washed away to start new colonies in other places. So we have to carefully remove the cut stems and let them dry completely.  Then they can be safely carried away and composted. This is why you might see piles of cut knotweed at different places on the trail. 

The method we are using is very labor intensive, but a small group can accomplish a lot and have fun doing it.  If you would like to help, contact, or check out the information and links on our volunteer pages