Stopping the Spread of Ivy
Late summer is the best time to kill poison ivy and English ivy. As both of these species have extensive root systems capable of regenerating from pieces of roots, they are nearly impossible to eradicate by digging them out of the ground. The heavy wax covering the leaves makes them difficult to chemically eradicate as well. An exacerbating factor with poison ivy is that mature plants generate seeds that can remain dormant in the soil for years. Their potential germination adds to the frustration of complete eradication.
If poison ivy is growing as a vine, climbing on tree trunks, phone poles or walls, the best and safest lethal method is to partially cut through the stems with a hatchet or sharp knife. Immediately after making the cut, place a few drops of weed killer on the cut surface. I prefer using Weed-B-Gone or Trimex.
Mix either of these materials with an equal amount of water. Using an oilcan or squeeze bottle, place a few drops of the mixture on the freshly cut surface of the stem. The sap flowing in the stem will carry the weed killer up and down the stem, killing the entire root system. This method can safely be used to kill vines growing on trees because the weed killer is carefully applied only to the vine and does not come in contact with the tree.
If the ivy is crawling on the ground or hip high, you will have to use the weed killer as a spray. Weed-B-Gone, Trimex or glyphosate (Round-Up) will do the job. Use any as directed by the manufacturer, adding one rounded teaspoon of ammonium sulfate to each gallon of spray. The ammonium sulfate dissolves the leaves’ oily covering, allowing the weed killer to penetrate the leaf tissues.
The ivy must be actively growing for foliar spays to work. Do not use if the plants are under drought stress.
When using any chemical spray, always wear protective clothing, rubber boots and rubber gloves. Use only low pressure for the spray so it falls in large droplets. To prevent drift, spray only when the air is calm and only to wet the foliage. Avoid excess that can drip on the ground.
A sprayer used for applying weed killers should be dedicated to this purpose. Print Weed Killer Use Only on the tank. Rinsing the tank, hose and nozzle with washing soda, ammonia and water does not guarantee freedom from residues.
I have done research on weed killers since 1959, starting with Agent Orange. Treat them with respect and use them only when you must.