String trimmers are time and energy savers, and they are much easier on your back than good, old-fashioned hand clippers. While you might love your string trimmer, your plants might not. Trees, shrubs and vines in particular can suffer the most damage. Their woody stems and trunks can only take so much beating before they become girdled, negatively affecting their growth and vigor. If you have a vine in your garden, select one of several methods that will effectively protect its base from a string trimmer.
Remove grass and weeds manually around the base of the vine, extending 6 or more inches to create a circle that is 12 or more inches in diameter. Apply a 3- or 4-inch layer of mulch, such as shredded bark, around the base; however, maintain a distance of 2 or 3 inches from the vine’s stem to prevent rot caused by excessive moisture. Use the trimmer around the outside of the mulch ring. If necessary, hand pull or use hand clippers to clean up grass or weeds that grow right next to the vine's base.
Cut a piece of plastic pipe, such as a corrugated drain pipe, so it is about 6 to 8 inches long. Use heavy-duty or industrial cutting shears for this task. Also, cut the pipe down the side and wrap it around the base of the vine. Remove the pipe after trimming so moisture does not accumulate on the inside, keeping the base excessively moist and causing rot. (ref 2)
Wrap chicken wire or hardware cloth loosely around the base of the vine, securing the ends with wire or plastic zip ties. The trimmer can cause some damage to the base if it hits at the right angle, but the wire or cloth can be left in place without fear of encouraging too much moisture. Replace or loosen the chicken wire or hardware cloth with a larger piece as the vine grows, if necessary.