Asked September 11, 2017, 9:40 AM EDT

We have a fairly large garden with a big wed problem one of the weeds we are fighting has a extensive root system. We would welcome any help or advice that is available

Clackamas County Oregon

2 Responses

Weeds are survivors. Control can be very difficult. The first thing is to identify what weeds you have in your garden. If you send us pictures of the weed plant with close-ups of the leaves and flowers, we can probably identify it for you. Individual weeds require different control methods, but one principle is to remove weeds when they are small and before they develop their seeds.

Some of the most frustrating weeds are perennials with extensive and tough root systems. They can survive years on the nutrients stored in these root systems. The nutrients are manufactured in the leaves and are moved down into the roots. Really get rid of these plants takes starving the roots. When you remove the foliage the roots must use some of their stored nutrients to send up new shoots. By repeatedly and consistently removing the plant material above the ground they have to use up their stores, and you also prevent new nutrients from moving down into the roots. Eventually, you will starve out the weed. But it takes a while, and you always have to be vigilant for new growth.

Fall is a good time to treat these weeds with herbicides because the plants are moving nutrients down into the roots in preparation for winter, and the herbicides will be taken down into the roots as well. You can damage the weed this way, but if the root/rhizome area is extensive parts will survive. Watching for new plants next spring and getting rid of them when small is essential.

If you do use herbicides, use the safest ones, trichopyr (brush killer) or glysophate. Carefully follow directions for dilution and application methods on the herbicide container. Painting instead of spraying the herbicide on the weed can help prevent damage to your plants.