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Who doesn’t like to get “more bang for the buck?” The concept of combining an herbicide and a fertilizer may be good in theory, but may not work in every situation. Several potential problems exist when using this approach.


The first issue is the timing for herbicide application and fertilizer application usually aren’t in sync. Some weed and feed products contain preemergence herbicides that control weeds as they germinate and, depending on weather condition, are best applied before late February. Fertilizer applications for warm-season grasses such as Bermudagrass shouldn’t be applied until the first of May. Can you see the timing issue here? The two products really need to be applied at different times; therefore, using a weed and feed blend on bermudagrass in later winter/early spring isn’t advised.


Second, the selection of formulations for weed and feed blends is much more limiting than if gardeners were choosing only a fertilizer. Fertilizer formulations are much more diverse because fertilizer companies make many more types. Most companies that produce weed and feed products only make one type, which doesn’t allow gardeners to consider special nutrient needs that may have shown up in a soil test – for example, a need for less or more phosphorus. Here again, the best choice for gardeners is to apply weed killer and fertilizer separately.


The third concern is there’s more chance of over-application or misapplication of the weed killer. Because tree and shrub roots can also absorb many of the herbicide products, care in applying the herbicide is very important. In fact, many of the herbicide products state they should not be applied where roots of desirable trees or shrubs are growing. Research has shown the roots of many tree species extend well beyond the dripline of a tree. So, how should gardeners apply a herbicide to turf areas with trees growing in or near them? By using separate fertilizer and herbicide products and avoiding weed and feeds.


Another common problem is over-throw of the product into areas that have sensitive plants growing in them, including flower and shrub beds. This typically occurs when using the wrong equipment, such as a broadcast spreader rather than a drop or gravity spreader. Once again, it makes good sense to apply products separately allowing for more accurate rates and distribution.


Lastly, why treat healthy grass with something it does not need and could potentially weaken it? By the way, a weakened turfgrass is more likely to have weed problems. Spot treat only the weed-prone areas.


The real way to address weed problems is to start with improving turf management. A vigorous, healthy lawn can choke out most weeds. For information on recommended turfgrass management practices, see OSU Extension’s fact sheet on Lawn Management in Oklahoma.

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