Canadian County OSU Extension Service

Roundup the Weeds

Have you noticed that some grass around town appears to have been painted green in the past few weeks. Well, if you are wondering what this is and why they have done this, I have your answer. 

This artificial green color is not paint, but is a product used so people can see where spraying has occurred. This ensures that spray is only applied to the intended target. 

This dye is not necessary in most cases, but in the commercial horticulture industry it is often used so the client can see that their landscape is being maintained. 

So why would they be spraying grass in the middle of the winter? 

Well, if you have a Bermuda grass lawn hopefully your yard is a pleasant dormant wheat color.  However, if it is spotted with green winter weeds, now is the time to spray Roundup with the active ingredient being Glyphosate. 

Roundup is a non-selective post-emergence herbicide. This means that it will kill or injure most green, actively growing plants. For a plant to be actively growing usually requires several days of temperatures above 50°F.

Annual bluegrass and other winter annual weeds can be controlled with applications of Glyphosate on fully dormant Bermuda grass in December, January, and February. Do not make applications after Bermuda grass begins to green-up, and always make applications at the label rate.

All post-emergence herbicides also can be termed either systemic or contact. Contact herbicides kill or injure only those plant parts that they directly come into contact with.

However, Roundup is systemic.  Systemic post-emergence herbicides are absorbed by plants and translocated to all plant parts, including underground bulbs, nutlets, and rhizomes. Perennial weeds, with underground plant parts, are most effectively controlled with systemic post-emergence herbicides.

Post-emergence herbicides, including Roundup, are generally foliar applied then absorbed, so they must remain on the leaf surface for 24 to 48 hours following application for adequate absorption.

Therefore, check the weather to make sure that it will not be raining shortly after application. Also, do not mow several days before or after herbicide applica­tion to ensure that the herbicide has plenty of surface area and has time to translocate down into the weed.

If you would like more information on managing your lawn please visit our website where you will be able to find the link to OSU fact sheets F-6423 and HLA-6421.

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