![This lawn shows weed-and-feed damage that can occur in area lawns. [Special to the News Bulletin]](http://127.0.0.1/wordpress/wp-content/uploads/2022/01/ghows-DA-49877b25-3d39-75ed-e053-0100007f30e0-149d8c52.jpeg)
The weed-and-feed concept is very popular. Fertilizing a lawn and controlling weeds at the same time sounds like a winning combination.
But be cautious — it's not foolproof.
When the herbicide (weed killer) in a weed-and-feed product is a pre-emergent, the product must be applied prior to weed emergence.
Applying a pre-emergence herbicide, after weed emergence (when weed seedlings are visible), will have little or no effect.
In general, a pre-emergence herbicide should be applied Feb. 15 to March 1 in North Florida, when day temperatures reach 65 degrees to 70 degrees Fahrenheit for four or five consecutive days. This is about the time that azaleas and dogwoods first begin to bloom.
Many common weed-and-feed products contain high amounts of nitrogen fertilizer. Nitrogen stimulates top growth in lawns. Applying a high-nitrogen fertilizer too early increases the likelihood of frost or freeze injury to the tender new growth induced by the early nitrogen application.
If the weed-and-feed is applied mid-February to early March (as a pre-emergent), it's too early for the fertilizer. If it is applied mid-March through April (as a fertilizer), it's too late for the pre-emergence.
There are additional concerns with the weed-and-feed approach, which:
*Does not lend itself to spot treatment of small weed-infested areas in a lawn, because fertilizer is typically applied throughout the lawn.
*Does lend itself to blanket application of the herbicide, even where weeds aren't a problem; again, because the herbicide is mixed with the fertilizer.
*Herbicide can easily end up on paved surfaces and ultimately in waterways.
*Many weed-and-feed products contain too much nitrogen and too little potassium.
*Herbicide in some weed-and-feed products can injure nearby trees and shrubs.
*Overuse of some pre-emergence herbicides can result in stunted lawn roots.
*Pre-emergence herbicides can interfere with lawn-grass seed germination.
*Some pre-emergence herbicides can severely injure newly sprigged lawns.
Give these considerations some thought and you may decide to do your weed control and fertilization separately.
It is the user's responsibility to read and follow all label directions and precautions when applying any pesticide, including herbicides.
Larry Williams is an agent at the University of Florida's Institute of Food and Agricultural Sciences Extension office in Crestview.
This article originally appeared on Crestview News Bulletin: 'Weed and feed' is not foolproof