How to use herbicide effectively on perennial weeds

I am having guests for most of September, so I did a cursory clean-up. I moved all the piles from the guest room to other locations, flicked a dust rag around and vacuumed. And I spent more time in my garden. No one who stays with me expects to see a ‘Martha’ home, but I take pride in my garden - even in its chaos.

Bindweed on the roadside, healthy even bone dry in bad soil.

I got down on my knees and finally pulled the bindweed out of my chipped-wood path. Bindweed is this amazing vining weed with a little morning glory flower. It is the scourge of gardeners with endless underground roots. I realized early on in my gardening life that bindweed would always win the battle, so I don’t stress about it. We have an understanding – I will leave it alone until it starts to bloom, then I will pull it up. I don’t need it going to seed and spreading that way in my garden.

Because of its extensive root system, it seems no matter how you much you pull it up, you never get the entire thing. Herbicide seemed an easier solution, but I usually opt for hand pulling. I have a friend who used to fight bindweed with herbicide, mainly glyphosate– known by the commercial name Roundup.

Roundup is an effective all-round plant killer and is widely used by home gardeners and in agriculture. It has the reputation of being fairly benign- so much so that a friend used to spray in sandals and shorts, in spite of my suggestions to wear protective clothing. (Happily, she became a beekeeper and this totally changed her weed control techniques.)

It is not benign, it is an herbicide. It is found in much of our food and if you start to research it, there is a huge amount of solid research and ridiculous misinformation out there. I am not advocating for or against herbicide use, just telling you that you need to be aware of its long term impacts and to use it wisely. Use it when it is most effective and realize it takes several days to kill the plant. More is not better.

Don’t spray it as if it is water and has no lasting impact on you or the environment. Spot spray, don’t broadcast spray. READ the label so you understand: when to spray so that it is most effective; how much to apply; and how to dispose of the container.

You'll be much more successful if you can control your seedling weeds early in their life, especially the annuals – which mean paying attention to what is growing, especially after summer rains. I use glyphosate mostly in the fall (before the first killing frosts) when the perennial weeds are starting to go dormant, but are still actively growing. Herbicides are absorbed deep into the plant as it pulls nutrients into its roots for winter storage. This is an effective application technique for many of  your perennial weeds which have large underground root structures.

Fall application on annual weeds doesn’t do any good. Folks around here are busily spraying annual weeds like kochia and another tumbleweed, Russian thistle, which have already lived their lives and made their seeds. These annuals break off at the ground and roll along in the wind, spreading their seed for miles. Spraying them now does nothing but give you a brown weed and waste herbicide. Their seed is ripe, they will still break off and roll.

Here is an example of useless herbicide application. Notice all the healthy kochia, covered with mature seeds and ready to die, break off and roll around, dropping seeds wherever it rolls. The herbicide on dead kochia in the background did nothing to prevent seed dispersal.

In your yard, it is better to cut the stems at the ground while these plant are younger, green and still developing their seeds. Bag the plants, and any annual weeds, to control the spread of their seeds. It takes more work certainly, but it is far more effective for control and far better for the environment.