I would like to know at what time of year will it be more effective to cut a grapevine, apply Roundup and Ensure that it doesn't sprout back. Spring or fall?
When to Kill Grapevines Most Effectively
Certified GKH Gardening Expert
Spring is the very best time, but hot days in the middle of summer are a close second.
The easiest way to kill gravevines with Roundup, is to cut the vine, completely if you can. Paint the cut with concentrated Roundup. When the plant is in full growth mode (spring) or is trying to keep up with the heat (hot days), its vascular system is in overdrive. When it gets cut, it does not realize it right away, so adding the Roundup causes it to suck it into its root system and kills it.
With tough vines like this, you may need to repeat it 2-3 time, but it is the fastest way to kill the vine.