We observed possible kudzu control on community sites where grass clippings was used as land fill (first photograph, June 2005). Kudzu did not appear to root in it, and it thereby acted as a barrier. One advantage of grass clippings is its low cost and wide availability. This also suggested testing other mulches as barriers. While kudzu sometimes grows over piles of mulch, it does not appear to root well, possibly due to dryness or the heat caused by sunlight (or both). The second photograph shows a pile grass clippings at our test site. August 2005.
We were surprised when a pile of grass clippings placed on top of vigorous kudzu in buffer zone showed high interior temperatures due to composting (first photograph). That pile was left undisturbed during one season, and then pushed back (away from the sign in the second photograph). No living kudzu was found underneath. Apparently the high composting temperature "cooked" the kudzu during the summer, and killed not only the above ground foliage, but the crowns in the ground too. Photographs are for August 2005 and May 2006.
Other kinds of mulch also appear to inhibit kudzu growth in landscaping (first photograph). These mulches are more widely available than grass clippings, either as a commercial product or as a byproduct of landscape maintenance (second photograph). Photographs are for May 2005 and July 2005.
Like grass clippings, kudzu grows over, but does not root well in other mulches. Such kudzu is therefore easier to roll back. However, we have observed that as the mulch ages, it becomes less effective as a barrier to kudzu. The reason is because kudzu begins to root in the decomposing mulch, the same reason homeowners must occasionally add new mulch to prevent weed growth in their plant beds. July 2005.
This April 2006 photograph shows that grass clippings (foreground right) is a superior mulch for controlling kudzu than wood chip mulch (background left): One year after treatment, there are no flags in the grass clippings mulch to indicate that rooted kudzu plants were removed, whereas the wood chip mulch has abundant yellow flags (background left).
Experience with Mulch to Control Kudzu
Many years ago when our Company purchased our building and land the building had been vacant for some time. The building sat in front of a large hill leading to a prominent stream feeding into a prominent river. Kudzu was growing across the parking lot from the hill to the back of the building. The growth was very pronounced on the hill and on the trees on the hill and down to the stream. We started cutting back the growth, but as it does it came right back. We used Round UP for years along with cutting and this only kept the plant at bay away from the parking lot. Every year it grew up very tall. This costs us time and money in labor and materials.
We had developed some erosion in some areas so I started thinking of ways to get this under control as well as the kudzu. My assistantís husband during the latter years had started a tree cutting business. She mentioned that dumping the "sawdust" and "mulch" was difficult when he was downtown close to my office building since he would have to drive a long ways to a dump to dispose of it. The idea was born to bring the mulched wood to our hill and dump it there. It was natural anyway and posed no threat to our property or aesthetics. People put mulch around the plants I thought and the city would not complain about that. Perhaps, it would keep the kudzu back and maybe smother it or kill it. So we started the process. He would come by frequently to smooth out the little hills with his front end loader. It saved him money and time and our Company as well. The interesting thing about the wood chips was that it was very warm when he brought it. The heat escaping from the cut wood would steam for some time. It could be argued that this heat and fermentation was helping to kill the kudzu and keep it from encroaching upon our property further. Pine, Poplar, and oak were the main cuttings dumped. The nature of the wood might have had some bearing on our success as well. More testing would be required on this.
For several years now we have been keeping the kudzu at bay this way, saving our Company money, giving the tree cutter savings and a convenient dumping place. This not only kept us from having chemicals run down to the stream helping the quality of the stream, but we were using a natural solution which didn't look bad. We had no artificial method such as poly overlay to trap heat. The city has not complained. Who knows after the wood matures and we accumulate enough we may be able to be in the mulch selling business.
President, International Industries Corp.
880 East Main Street
Grass Clippings: The Bottom Line