How do you kill thistles that I got from bagged soil in my garden? They get worse every year.
The Gardener’s Answer
Hi, James: Getting rid of thistles in the garden can be quite an undertaking, especially if they have had time to multiply. Thistles are weeds that have an extensive tap root making it even more difficult to get rid of them. Hand pulling or digging, which is more likely the case with this weed, can be a remedy for a small garden but for a larger one this may not be feasible. Round-Up is an herbicide used for spot spraying. This product contains glyphosate, which will kill most any plant it comes into contact with, so it must be used with caution. For a more natural control, not allowing the thistles to flower will help. Once they flower and the seeds are dispersed, the task of removing them becomes a tougher one. The younger the plants are the easier it will be to remove them. Cutting back the existing foliage and then covering them with newspapers or cardboard and then a thin layer of mulch will prevent light from filtering through and the roots will not survive. Getting control of them now will help keep the population down. For future reference, purchasing high-quality soil or amendment products from a reputable garden center will ensure that you are not adding potential weeds to the garden.