Does Roundup Hurt Shrubs?

Roundup's Actions

• As a systemic herbicide, Roundup’s active ingredient glyphosate penetrates the entire plant through its green, soft tissues such as leaves and stems. This moves through the plant to the roots, effectively killing the targeted plant. It’s a non-discriminating herbicide, although it doesn’t kill seeds in the soil, nor does it penetrate thick tree bark. It’s inactive in soil.

Application

• Roundup comes ready-to-apply in a liquid form in spray bottles with pumps or one-touch wands, and is also available in concentrate that you mix with water. A low-drift, ready-to-use foam version improves your ability to target plants in tight spots. Home-made favorite dauber methods for tight spots use paint rollers, sponges, and pruners or clippers treated with Roundup to directly transfer Roundup to the plant. Remember, though, to thoroughly clean the pruners or clippers with warm, soapy water before use on desired plants -- or dedicate these to future applications of the herbicide.

Environmental Conditions

• Risk of drift always exists when using spray herbicides. Directed spraying is best done when the air is calm and winds under 10 miles per hour. In windy conditions, small droplets of spray drift long distances, causing damage to nearby plants. When applying Roundup, especially in tight locations, the use of cardboard or commercial plant shields is highly recommended. [References: 4, 8, 9]

Shrub Precautions

• Non-selective systemic herbicides like Roundup do not enter through thick, woody barks of trees, but they pose a risk to thin-barked trees and shrubs and shrubs with green, photosynthesizing trunks. Numerous university extension reports describe damage on shrubs from using glyphosate herbicides around woody plants. Unintended contact with shrubs might not be fatal, but the herbicide is absorbed by the plant through the leaves and green stems, and thin trunks and stored in the stems and roots. The damage often shows the following spring when new growth appears stunted.

Prevent Damage

• Timing is important when applying Roundup around shrubs. Treat weeds close to shrubs using shields, even when the plant is going dormant. Use caution to protect the shrub’s foliage from drift. If the shrub suckers around the base, be aware that suckers are vulnerable to glyphosate; damage won’t appear until the plant breaks dormancy. Consider manually removing weeds close to valuable shrubs as an alternative.

Injury Treatment

• Removal of the injured portion of the shrub is ineffective. The herbicide will have moved through the leaves and into the roots by the time you observe the damage. If you suspect herbicide injuries, consider revitalizing your shrub with an appropriate fertilizer, especially if you notice the damage in the spring.