April 22, 2016
Fertilizing Lawns & Crabgrass Control
This has been a strange spring for weather, but anymore I’m not sure what a normal spring is. We started wet, but it soon turned dry. Our temperatures alternated between those typical for mid-March and mid-May, but gradually warmed to where the soil was almost warm enough for crabgrass to germinate. Now that we finally got some much needed precipitation, it will drop soil temperatures back.
But, after a month or more of telling people it’s too early to put on their crabgrass preventer and first fertilization of the year, we are finally in that time window. I aim for the first of May, give or take a few days, to make that first treatment to my lawn. Crabgrass will germinates when soil temperatures are sustained between 55 and 60 degrees. So preemergence herbicides for crabgrass should be applied in the next week or two.
Crabgrass preventers work by killing seeds as they germinate, they will not kill weeds that have already emerged. So you should delay applying any of the common preemergence products on areas that winterkilled and need to be reseeded or on any newly seeded turf areas because they can reduce your turf stand if seed is still germinating. However, they are fine to use on new turf once it has emerged.
Special preemergence products such as Tupersan (siduron) or Tenacity (mesotrione) can be used on a new cool season turf seeding and will kill the crabgrass seeds as they germinate, but not the cool season grass seeds such as bluegrass or fescue. You may have to go to a garden center to find these specialized products as they are not as widely available.
Since I mentioned fertilization, let’s recap our recommendations for fertilizing cool season turf grasses such as bluegrass or fescue. I recommend and fertilize my own lawn with a small amount, maybe a half pound of actual nitrogen per 1,000 square feet or turf, at four times throughout the growing season. The best way to remember these is to fertilize by the holidays... Arbor Day or May Day (late April to early May), Memorial Day (late May), Labor Day (early September), and Halloween (late October).
The advantage of spreading out the fertilizer applications and waiting for the first application until around the first of May is this avoids the burst of growth that follows an early spring fertilizer application. While rapid growth in the spring seems like the sign of a healthy lawn, it actually sets the lawn up for more problems during stressful periods in mid-summer.
Some homeowners are not willing to fertilize four times, they only want to fertilize twice... once in the spring and once in the fall. In this situation they will still want to make their first application around May 1 and then wait until Halloween for the second application. This late fall application is the most important application we make all year, even though most above ground turf growth has slowed or even stopped by then. It will give you a nice even greenup the following spring without a rapid flush of grass.
The reason this might not be the best for your lawn is turf often needs a little fertilizer in early September to help recover, especially if it has been a particularly stressful summer, but the late October application is still the most important of the year. If we do have a particularly stressful summer on lawns, you may be able to get by with one application this spring, but still need to split the fall application, early September and late October.
For more information on spring lawn care, contact your local Nebraska Extension office.