Pascual Hernandez
Pascual Hernandez

This time of year we get questions regarding fertilizer, herbicides, or using “weed & feed” products on lawns.

The idea of combining a herbicide and a fertilizer sounds like a good way to “kill two birds with one stone”, but may not work in every situation. Several possible problems exist when using this approach.

For starters, the timing for herbicide application and fertilizer application are frequently not in sync.

Some weed and feed products contain pre-emergent herbicides (that prevent weeds from germinating) and should be applied before late February.
Fertilizer applications for warm season grasses such as Bermuda grass should not go on until the first of May.

Therefore, using a weed and feed blend on Bermuda grass in late winter/early spring is not advisable; the two really need to be applied at different times.

Secondly, the selection of formulations for weed and feed blends is much less than if one were choosing only a fertilizer.

Fertilizer formulations are more diverse because fertilizer companies make many more types. The majority of companies that make weed and feed products only make one type, so you might not be meeting nutrient needs that may have shown up in a soil test. But if you increase the rate, there is greater probability of over-application of the weed killer.

A third problem is that we need to be careful if applying weed and feed because tree and shrub roots can also absorb many of the herbicide products.
In fact, many herbicide products state that they should not be applied where roots of desirable trees or shrubs are growing. However, we know that the roots of many trees extend well beyond the drip line.

Weed and feed products can be useful, but only if the applicator understands the possible hazards and can effectively deal with them. For more information, contact the County Extension Office.