Constant weeding and mulching are what it takes to keep weeds from germinating.
Q: By the middle of the summer, I'm so sick of weeding I could scream. Can you recommend anything short of herbicides that might help me get these bothersome interlopers under control? Any tips would be greatly appreciated.
—W.M., New York, NY
A: One of the best controls is a smothering mulch. This can be layers of newspaper or cardboard covered with a few inches of shredded bark, pads of straw, chopped leaves, partially finished compost or whatever you have available at reasonable cost. This keeps the weed seeds from germinating and as an added bonus feeds the soil as it decays.
The next defense is to keep any existing weeds from going to seed so you can stop the next generation. Hand weeding is easiest right after a rain so the roots come out of the soil cleanly and easily. (If you pull off only the tops, the weeds will regrow.) Most weeds, even persistent perennial weeds, will succumb to repeated decapitation and grubbing as the root reserves are worn out. After a year or two of mulch and concerted use of the other measures the weed problem will never be as bad again.
Finally, the occasional truly pernicious weed might deserve a bit of glyphosate applied very carefully and according to the label instructions for spot weeding. Be aware that patience is required for this as it may take quite a long time for the chemical to translocate to the root. Good luck with your weed war!
— National Gardening Association