Landscape - Fall is the Time to Control Perennial Weeds and Invasive Plants

Target perennial weed control now in landscapes. The following is more information.

The second half of September is a good time to control many problem perennial weeds using systemic herbicides. At this time of the year, perennial plants have shifted from top growth to moving nutrients downward to areas of the plant involved in winter survival (crowns, roots, rhizomes, bulbs, corms, or tubers). Food reserves are stored in these plant parts and are needed to produce new weed growth in the spring. Systemic herbicides often will be more effective during early fall as they are translocated with this downward movement of nutrients in the perennial weed plant. Early fall applied herbicides also disrupt the downward movement of nutrients by killing foliage thus reducing the amount of carbohydrate that can reach storage organs. Perennial weeds that do not store adequate carbohydrates will have reduced winter survival or will be weakened next spring. Herbicide applications to perennial weeds should be made several weeks prior to the first hard frost for best effect. Examples of early fall perennial weed control programs would be glyphosate on mugwort, fluazifop-P-butyl on bermudagrass, triclopyr on Canada thistle, as well as selective herbicides such as 2,4-D, triclopyr, dicamba and clopyralid for perennial broadleaf weed control in turfgrass.

Now is also the time to control problem invasive woody species like poison ivy, multiflora rose, honeysuckle, bittersweet, fox grape, or porcelain vine. Herbicides containing glyphosate or triclopyr will be effective on these woody invasives as they both translocate readily into root systems this time of year and good control is achieved.

Information from Gordon Johnson, Extension Horticultural Agent, UD, Kent County