An Easy, Effective Way to Control Perennial Woody Weeds in Home Landscapes

Perennial woody weeds are often problematic in ornamental beds. Homeowners often use hand removal to quickly get rid of the unsightly weeds, but new shoots emerge quickly. In fact, hand removal of old growth often stimulates perennial weeds, especially vines, to produce more new shoots. Hand pulling vines, such as poison ivy, can cause a severe rash outbreak if you are allergic, and the oils that cause the allergic reaction can contaminate gloves.

Treating perennial woody weeds with herbicides can be a more effective long-term control solution. In areas where you also have desirable plants, it is best to use herbicides with no soil residual activity. Herbicides that are active in the soil may be taken up by plant roots and damage desirable ornamentals.

Roundup (active ingredient: glyphosate) is an ideal treatment for perennial weed control because it has activity on a wide variety of perennial weeds, it is not absorbed from the soil by plant roots, it is inexpensive, and it is widely available. However, Roundup must be applied with extreme caution to avoid spray drift onto desired ornamentals, which can be seriously damaged or killed by the herbicide. Wiping the Roundup solution onto the foliage of weeds can be an effective application method with significantly less potential for drift. This method may not apply enough Roundup on the foliage of the undesirable plant for satisfactory control, especially if woody perennial plants are the target.

Homeowners wanting to improve control of woody perennials can use an herbicide application often used to control trees. In this method, an herbicide is applied to the stump immediately after a tree is cut, often preventing new sprouts from emerging from the stump. This method works best for complete control if done in the fall when sugars produced by the plant are moving into the roots in preparation for winter dormancy. To control perennial woody weeds in ornamental beds, you can apply Roundup with a florist’s water-pick (Figure 1).

A water-pick is a plastic tube used by florists to maintain the quality of cut-stem flowers. It has a rubber cap with an opening that stretches around the stem for a water-tight seal. Water-picks vary in size, but those evaluated for this publication were 3–4 inches long and held approximately 0.7 fluid ounce.

Fill the water-pick with undiluted (41 percent isopropylamine salt or 48 percent potassium salt) Roundup (approximately 0.3–0.7 fluid ounce), and seal with the lid. Find a stem on the target weed that is slightly larger than the hole in the water-pick cap. Cut the stem with pruning shears, and then slide the water-pick onto the cut stem. Make sure the cut stem is positioned so the plant can absorb all the Roundup in the water-pick (Figure 2).

To kill the entire plant, including the roots, remember to use this technique in the fall (August to late October) when the plant is moving sugars to the roots. The only potential for damage to ornamentals is if the tube is dislodged from the stem or the stem is too small to seal tightly, which could result in Roundup spilling onto adjacent ornamentals.

As with any pesticide application, always read and follow label directions. Pay particular attention to the Personal Protective Equipment (PPE) section for handling pesticides and pesticide containers.

The information given here is for educational purposes only. References to commercial products, trade names, or suppliers are made with the understanding that no endorsement is implied and that no discrimination against other products or suppliers is intended.

Publication 3808 (POD-01-24)

By John D. Byrd, PhD, Extension/Research Professor, Plant and Soil Sciences; Jim Taylor, former Senior Research Associate, Plant and Soil Sciences; and Victor Maddox, PhD, former Senior Research Associate, Plant and Soil Sciences.

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