Jingjing Yin, Commercial Ornamental Horticulture, Cornell Cooperative Extension Capital Area Agriculture and Horticulture Program

Goldenrod (Solidago) is a genus of herbaceous perennials in the aster family with up to 120 species and numerous cultivars. It is a tall and slim plant about 2-5 feet in height. It displays small, bright yellow flowers in dense clusters on top of tall stems from August through October. The blooms provide an enormous amount of pollen and nectar late in the season which attract bees, wasps, and butterflies. Birds are fond of its seeds. It is also deer resistant. Many home gardeners grow goldenrod in their yards. Native Americans and Chinese use this plant for medicinal purposes.

However, goldenrod can be considered as a weed in certain circumstances. For example, Canada, or common Goldenrod (Solidago canadensis) is one of the most prominent of the species of goldenrod native to America. It thrives mostly in moist conditions and is fairly intolerant of shade. It is often found in open areas such as meadows, prairies, and the edges of woodlands. It can be a weed in perennial crops such as Christmas trees, blueberries and pastures. It has strong colonizing ability. One Canada Goldenrod plant produces over 20,000 seeds. The seeds can be dispersed widely by wind and quickly establish in bare soil and in places where competition from other plants is light. Once established they spread rapidly by roots. Their fibrous root system produces rhizomes that form dense colonies. These colonies can exclude all other plant growth and grow to a substantial size, making them a concern for growers and farmers. Therefore, if it outcompetes the main crops or is reducing the plant diversity of a prairie, it should be controlled.

When the population is small, thoroughly and repeatedly hand pulling the stems and root mass can be effective. When trying to control large colonies, mowing in intervals for a few years will eventually eradicate the weeds. Allow plants to regrow 8-12 inches between mowing sessions. In addition, remove flower heads before seeds ripen to mitigate seed dispersal.

When using herbicides, late summer and fall are good times for applying glyphosate as plant sap movement is mostly directed toward the roots where nutrients will be stored in anticipation of next season. Therefore, glyphosate can easily be translocated from leaves to roots, improving the herbicide efficiency at killing the roots. Make sure to apply glyphosate when the leaves are still green.

For more information, contact your local cooperative extension office.

 

References:

Cornell Weed Identification: Canada Goldenrod: https://blogs.cornell.edu/weedid/canada-goldenrod/

Rutgers Cooperative Extension – Plant & Pest Advisory: Fall control of perennial weeds with herbicides: https://plant-pest-advisory.rutgers.edu/the-season-is-over-for-blueberry-but-not-for-controlling-perennial-weeds/