Many weeds are not actually weeds if you research the individual plants. Many have benneficial uses. Weed killer is aweful for you & the environment! Depending on the plants that are present, I would tackle it a little at a time after you identify what's there. You can mow weed grasses or weedeat if you determine what is a plant and what is a detrimental weed, or you can hand pull. It is rarely a good idea in a healthy garden to use drastic measures like cutting on things with a chainsaw because that can introduce diseases into the wounds you create in the older plants. Usually, you would get various pruning sheers & disinfect them between plants to cut undesireable portions off to shape & care for them. You shouldn't cut major limbs, or more than 1/3rd of the plabt down for the health of the plant. Then you would hand pull the undesireable plants root and all before they go to seed. If you need to keep weeds at bay after you get it managed there are natural solutions like laying tarp, or cardboard down, weedcloth with ground cover, or planting living ground covers & other plants that out compete the weeds or are allelopathic (they put out chemicals in the soil that retard the growth of other plants). If the plants aren't toxic you can even get a pet to help eat the weeds like a goat or rabbit

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