For cool-season grasses:

Apply broadleaf weed control; Don’t fertilize in April

Adapted by Vickie Bell from article by Gil Medeiros, Fairfax Master Gardener

Early April is the right time to apply a pre-emergent product to control crabgrass or a post-emergent product to suppress many of the broadleaf weeds that sprouted in the winter. Many weed-control products are packaged with fertilizer, and that’s a problem. So, why is that a problem? Because its not the right time to fertilize your lawn. You may have to go to a garden center to find weed control products without the fertilizer. Many big-box stores carry only weed-and-feed. Resist the temptation to apply a weed-and-feed product.

Lawn care companies, big-box stores, your next door neighbors, your mailman…they all tell you to fertilize your cool-season lawn in April. The advertisements of nationally marketed fertilizers and the splashy promotions in the big-box stores are correct for some parts of the country. But not here in Virginia!

Resist. For the good of your fescue, bluegrass, and perennial rye, resist.

Here’s why. In spring, as grass awakens from dormancy, it wants to grow roots. This priority is hard-wired into their DNA from years of  accumulated survival wisdom. The grass sends its roots deep into the soil because summer is coming, the rain may stop, and the heat is certainly on the way. The timing of this root-growth spurt is not the same everywhere. It is governed by climate, which is a function of longitude and latitude. In Virginia, the fescue and bluegrass awakens to push out new roots in April and early May.

What happens when you feed the grass in April with nitrogen? Nitrogen helps the plants grow green, leafy shoots. When the plant is growing shoots, it slows and eventually shuts down the growth of roots. Root growth is, therefore, stunted as the grass plants take advantage of nitrogen availability to grow luxurious, green top growth. After fertilizing you feel secure in the knowledge that you have done the right thing by your lawn. It has never looked happier.

Fast-forward to mid-July. The weather is hot, and rainfall is sparse. It is natural in the heat of summer for grass to lose roots. If the plants grew enough roots in April, they can survive. If not, the plants are becoming weak. 

According to David McCall, a turfgrass disease expert with Virginia Cooperative Extension, over-fertilization in spring leads to increased Brown Patch (the most common lawn disease in our area), Pythium Blight and Gray Leaf Spot. Soon patches of grass are dead or dying.

I know that you are disappointed that you can’t fertilize in April, but cheer up! You can fertilize (at a rate not to exceed a half-pound of nitrogen per 1,000 square feet of lawn) in the latter half of May. By then, grass plants have completed their annual growth of roots and are ready to grow shoots above the ground. Don’t get overly aggressive. Any spring fertilization is a booster shot. Most of your fertilization should have been done the previous fall. So you have something to look forward to in September!

There are no guarantees in biology. However, we can say that grass not fertilized in April has a better chance of surviving tough, mid-summer conditions. Save yourself some time and money and just resist.

More information on lawn fertilizing can be found at Lawn Fertilization in Virginia, Publication 430-011, Virginia Cooperative Extension