How to Kill Hedges
You can also use a sturdy pitchfork or garden tine to dig into and remove the roots. While this is more practical for smaller hedges, it will help to turn the soil and guarantee that you have removed all of the roots.
If you use a root/weed killer, be sure that it is safe for the soil. Do not use gasoline or other harsh chemicals to kill roots, because they damage the soil and nothing else will be able to grow in that spot.
Unkempt hedges can be an eyesore. A number of people plant hedges only to realize a few years down the road that they don't want the responsibility and the work that hedges require. Sometimes your landscaping plans just don't include hedge care, and you want them gone. You don't have to hire expensive landscape contractors to remove the hedges for you. Although it can be a bit time consuming, you can easily remove hedges and kill the roots yourself.
Cut down your hedges. The first and most important step to killing hedges is to cut them even with the ground. This can be done easily with hedge clippers, unless they are very mature hedges. A very old and developed hedge may require the use of a small chainsaw.
Find the roots. You will need to find the roots and get rid of them or the hedges will continue to grow back. Begin tracing the roots in the area where you have hacked the hedges.
Dig up the roots. The majority of hedges don't have deep roots unless they are very mature. The roots are relatively easy to find and are normally within a 6- to 8-inch area. Depending on the type of hedges that were planted, the roots might be in a ball shape around 6 inches deep into the soil.
Remove the roots. If you find that you can't dig up all of the roots because they are too big or deep, you can resort to Roundup or another root/weed killer. Check with your local nursery or garden center to make sure that you are using a chemical that is safe for the soil.
Spray the roots generously with the root/weed killer. You will have to re-apply the chemicals on a regular basis and wait for the roots to rot and die out. This could take several weeks and a number of applications of the chemical. Once the roots have died, remove them from the ground and discard. Consult your root killer's documentation for application frequency.