25July 18, 2019

With the forecast for the first heat wave of the season, you may be tempted to stay in the house and ignore working in the yard. The hot, sunny and humid weather is ideal for one project in the yard. The project I am talking about is killing poison ivy.

If you look around your yard, you may see a lot more poison ivy growing in places where you have never seen it growing before. Poison ivy forms berries later in the season and the birds love to eat the berries. The berry contains a seed that will create a new plant. The bird can’t digest the seed and the seed eventually passes through the bird’s digestive system and ultimately comes out, well, you know. The seed drops on the ground and sooner or later a new plant is born.

The other thing that you need to know is that with the rise in CO2 in the atmosphere, poison ivy is growing stronger and the oils in the leaf are a lot more virulent. Some scientists have dubbed the plants that are showing up now as super poison ivy.

If you are not familiar with poison ivy, the plant has three leaves in a cluster and at this time of the year the leaves tend to be glossy green. As a kid, I always heard that “leaflet 3, leave it be.” Early in the spring as the new growth comes out, the leaves can be red in color for a short period of time.

Poison ivy is known as a woody plant. This means that it is tougher to kill. During the warm weather of summer, poison ivy grows like crazy. This attribute of growing faster in hot weather makes it easier for you to kill the poison ivy.

You will need to buy a weed killer that works on woody plants. The issue with weed killers that kill poison ivy is that the weed killer will kill any other plant. For example, if you have poison ivy growing near a rose bush and the spray gets on the rose bush, it can kill the rose bush. Knowing this, you do not want to spray a weed killer on poison ivy on a windy day. The wind can send the spray onto desirable plants and kill those plants too. Also, it is best to spray the poison ivy when there is no rain in the forecast for 24 hours. This allows the leaves to absorb the spray.

So you have decided to spray the poison ivy. There is a product called horticultural vinegar. It is 20% vinegar. If you spray this on the leaves of the poison ivy, it often kills the poison ivy right down to the roots.

You have to be extremely cautious using this product. If you get it into your eyes, it can damage your eyes. Ditto for getting it on your skin. Wear goggles and waterproof glove. Wear long pants and long sleeves. Horticultural vinegar is applied full strength.

There are also some organics that use clove oil as an active ingredient. The clove oil fries the leaf and may do some damage to the roots of the poison ivy. A second application may be necessary when new leaves appear.

On the chemical side, if the label says it will kill woody plants then you are good to go with using that spray. Keep in mind that the spray will kill other plants so be careful with applying it.

Because poison ivy has that shiny leaf, that leaf has a waxy coating that may allow the spray to roll right off. The spray needs to stick to the leaves, be absorbed by the leaves and ultimately carried down to the roots. If you mix 1/4 teaspoon of liquid dish detergent in a gallon of spray solution, the weed killer will stick better on the leaves. Once the spray is applied, it may take a few days to see signs of the killer working. The hot and humid weather is making the poison ivy grow faster and that makes the weed killer very likely to be thoroughly absorbed by the leaves.

Keep in mind that even after the poison ivy dies, the oils still are active in the stems and roots of the plant. Over time the oils dry out, but until that time, the oils can affect you.

Now is a good time to control poison ivy. You do need to follow the directions on the label. Please read the label and protect you, your family, pets and other plants by following all the label directions.

Well, that’s all for this week. I’ll talk to you again next week.

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