Will rocks and pebbles painted with lime prevent Johnson grass and other bad weeds from growing in a Japanese rock garden?
No, lime effects pH, it does not have any effect as a grass killer. You could apply weed killer with a paint brush to help get it under control. But you will have to be very careful with the application.
Name a product that can be used to kill the Johnson grass.
There is no magic potion for johnson grass eradication, but it can be done with some persistent effort. This article will tell you more: https://www.gardeningknowhow.com/plant-problems/weeds/controlling-johnson-grass.htm
Got some seed from for my canaries and thought about planting some in my garden but I don't want it to spread to the paddocks if it is poisonous to cattle.
Johnson grass can be toxic to our livestock, but only under certain conditions. It produces a toxin, prussic acid, when it is under stress (such as drought, freezing weather). More information can be found here:
My yard is infested with burr weeds and Johnston grass weeds. I keep pulling them out, but it seems they come right back! The Johnston grass grows right at the edge of the chain link fence so it's hard to get the roots for fear of breaking the bottom line. How can I get rid of these two invaders once and for all? Thank you!
Spot treating the weed with vinegar, boiling water, or Round-up may help. Also, for the burr weeds, this article may have some suggestions: https://www.gardeningknowhow.com/plant-problems/weeds/burr-medic-weed.htm
I have Johnson grass growing in a water front yard near the edge of the lake. What is the best method to get rid of it? I am concerned about using herbicides that close to the water.
You may want to check with your County Extension Office to find out the safest way to treat and remove this grass near a water source.
Here are some links to help you.
I live in a gated community where it is taking over large areas of grass.
Herbicides alone usually aren't enough to control Johnson grass. This article should help: