I have established beds with lilies, hostas, bleeding hearts, hollies, ornamental grasses, vinca, sedum, bulbs and annuals. I'm having a problem with numerous broadleaf weeds popping up through the sedum and vinca — thistle, dandelions, henbit, woodsorrel, purslane, yarrow, black medic and others, including grasses. Is there a product that can be sprayed “over-the-top” that would be safe to use in these beds? — via the Internet


Your problem has no easy answer. Rather, there is no easy labor-free answer. Because most landscape plantings include a mix of annual and perennials, broadleaf and monocot plants, nearly all post-emergence herbicides will damage some portion of your plants. You can use a combination of hand-pulling the weeds, loose mulch and pre-emergence herbicides. After pulling the weeds, apply a 2- to 4-inch layer of loose mulch. Select a pre-emergence herbicide labeled for the predominant weeds you are trying to control and apply as directed, either below the mulch or on top. From this point on, you should tend to the beds weekly. Continued use of pre-emergence herbicides will help prevent new seedlings from establishing.



What a big mistake! A client planted horsetails in her carefree perennial garden. That was two years ago and now they are taking over. How do I control these spikes in her garden? — via the Internet


There are several species of horsetails, also known as scour rush and mare's tails, in the genus Equisetum. While interesting to look at, most gardens can handle only so many horsetails before they take over. These ancient plants reproduce by spores, much like ferns do, which germinate in the spring. They prefer sun, but will tolerate some shade, and can grow in wet or dry environments. Digging out the plants is nothing short of difficult. Their limited green surface makes chemical control difficult; however, a number of chemicals have been mentioned as potentials for control, including diclobenil, glyphosate and paraquat. Check with your local or state agency for an updated list of possible products. The stem's small surface area will not absorb enough herbicide to control the massive root system, so you need to make multiple applications. One source suggests thrashing the stems to break up the waxy coating prior to spraying with herbicide.

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