Fall weed control is best for perennial weeds
If you have perennial weeds such as dandelion, clover, Canada thistle, ivy or blackberries, now is the best time to apply herbicides. Plants are sending food produced by the leaves down to the roots, so herbicides are transferred more quickly to kill the entire weed. Use lawn weed killers or weed and feed on your lawn. Roundup or similar products containing glyphosate are effective in areas where you can avoid spraying leaves of your ornamental plants. Roundup will not damage bark so it can be sprayed around trees. For woody weeds such as blackberry and ivy, brush killers like Crossbow are more effective.
Allen Wilson
Allen has been writing about gardening for over 30 years. He is a retired professor of Horticulture.