Q. Our garden has a fall-blooming clematis that just won't die. It tries to smother neighboring plants. I have tried Roundup, boiling water, vinegar and digging at the roots. Unfortunately, the plant is well-established close to the fence, making it hard to excavate the roots. Do you have any suggestions that won't harm a nearby rose bush?
A. This lovely vine with vanilla-scented flowers looks innocent enough, but it is one of our worst invasive plants. Begin by cutting it to the ground in late summer, before it has a chance to bloom or set seed. Treat the cut ends of the vines with an herbicide containing triclopyr, such as Ortho's Brush B Gon. Follow up by checking the area frequently for any seedlings so you can dig them out before they become established.
Q. I planted some junipers 10 years ago that are out of control. They are now five feet tall. Can I prune them without killing them off?
A. Junipers, like most conifers, do not have the ability to sprout new growth from the cut stubs of branches. Great care should be taken in pruning them so you don't end up with a disfigured shrub that is more a liability to your landscape than an asset.
The pruning protocol is simple. Identify the longest branches and follow them down to a point where they meet up with another branch, and cut off the long branch entirely. This will likely leave bare areas in your junipers. Repeat this pruning every few years to keep the juniper within bounds.
You may want to take more drastic measures and replant with another conifer that will fit the space more closely. One of my favorites is Silver Spreader, a short and spreading form of our native red cedar, Juniperus virginiana. Because it never grows taller than three feet, you can cut long branches back from the edge as described above and allow new branches to grow out to cover any bare areas created in the process. It is also less susceptible to pests and diseases than other species of juniper.