D.M. Kopec, Extension Turfgrass Specialist
Weed control agents for home lawns usually are sold in 1 or 2 types of products, either as a liquid, or as a dry granule (like a fertilizer). Granules are solid particles, which contain (in this case) a post-emergence weed control product.
Here we are talking about controlling broad leaf weeds that have already popped out of the ground, and that are already growing among the grass plants in the lawn.
For this to work properly, the broad leaf weed control agent has to come in contact with leaves of the broadleaf weed itself. This is important, otherwise the weed control will be minimal. So what does this have to do with granular products?
There is a little trick here.
1. The trick is to first water the lawn.
2. Then immediately after this (while the lawn and weeds are still wet) apply the product across the lawn.
This is done in this order, so the granules will dissolve on the leaves of the weed directly, and come in contact with the weed.
If we do this in the reverse order (apply the post-emergence granule product first, and then water it in), the granule will dissolve and wash off down to the soil surface. This can greatly reduce the weed control response.
Post-emergence weed control granular products have a low concentration of active ingredient. They are made this way to insure ease of application, and uniformity of product distribution.
Don't confuse post-emergence weed control (using granules), with pre-emergence weed control products (using granules).
Pre-emergence products should be:
1. applied to the lawn,
2. and then watered in thoroughly.
This insures that the active ingredient gets down to the soil where it works best so it can come in contact with the weed seeds.
Also note, that WEED ‘n' FEED products contain a fertilizer, with a herbicide on the same granular product.
Make sure you know if the weed control agent is a pre-emergence or a post-emergence control product.
Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, James A. Christenson, Director, Cooperative Extension, College of Agriculture & Life Sciences, The University of Arizona. The University of Arizona is an equal opportunity, affirmative action institution. The University does not discriminate on the basis of race, color, religion, sex, national origin, age, disability, veteran status, or sexual orientation in its programs and activities.