I have 2 yellow Jackmani clematis growing, one on each side of a walk through trellis which is located in the middle of a large flower garden. Both grew great for about 6 years, but for the last 4 years, one of them sends underground shoots which pop up in the surrounding lawn, and in among my other plants, etc. Some of these shoots show up 6 feet away from the host plant. Last year we dug down and put in a metal barricade wall which is down to a depth of about 14." We thought that would solve the problem. This year, I have shoots showing up in the flower garden again. I dug down last night and tried to follow where they are coming from. They are coming from underneath our barricade wall. There were 6 stems coming from underneath. Why is this plant doing that, and how can I prevent it from happening? If I just cut them off below ground, it sends twice as many shoots up as if it's determined to do what it wants to do. There haven't been any new shoots coming up where they are supposed to so the plant is looking quite thin compared to the other plant. I should also mention that in mid summer, the leaves on the bottom 2 feet of this plant turn black and die off. The top part of the stems look very healthy and continue growing and they even bloom. This once beautiful plant has become my nightmare so I would appreciate any suggestions you can give me. Thank you.
Clematis Stems Running Underground
Certified GKH Gardening Expert
Have you had the soil where it is suppose to grow tested? When normally well behaved plants get out of hand, it tends to be because where they are currently growing has become unsuitable. It is likely trying to make a last ditch effort to keep itself alive, by growing outward into areas that it likes better. Have the soil tested to see if you are lacking anything. Make sure the plant is happy in other factors as well, such as water, sun and soil compaction.