2018 has been an interesting year so far in terms of weather. It is barely into March, and we have already seen sub-freezing nightly lows and above 80 degree high temperatures within a week of each other. These types of weather swings can be confusing to us, as well as our landscapes.
I have fielded several calls in the past few weeks about how to deal with Bermuda lawns during this time of up and down weather patterns. Some lawns have already started a slight green-up, or when the Bermuda comes out of its winter dormancy. You will see this more on lawns that face South.
The main concerns are whether Bermuda that has started to slightly green up should be fertilized, and whether it is too late to effectively put down a pre-emergent herbicide to control weed seeds.
Of course, experiencing daytime high temperatures of 80 degrees and soil temperatures around 65 degrees in February is not normal. These conditions have certainly caused some of the summer annual weeds in the weed seed bank in your soil to begin to germinate. Many of these germinated seedlings will have been killed off by the sub-freezing temperatures we are now experiencing. However, some weeds could survive, and you will have to use an over-the-top spray of herbicide to control them.
Just because we have already seen some very warm days does not mean pre-emergent herbicides will no longer be effective on your lawn. My advice going forward is to treat this year like a normal year and apply a pre-emergent herbicide in mid-March, and again 30 days later. This application schedule will still protect your lawn from the vast majority of summer annual weeds seeds that could germinate.
I would avoid any fertilization of Bermuda lawns at this time. Bermuda is a warm season grass, meaning it thrives in the hot temperatures of summer. When a warm season grass breaks dormancy and starts to green up, this process uses energy stored in the root systems of the grass to complete green-up. Knowing this, we recommend that you not fertilize a warm season turf grass until it has greened up 75 percent or so. Waiting until this time helps to prevent fertilizer waste.
When you attempt to fertilize a grass before the majority of the stand has greened up, you end up wasting most of the Nitrogen content of your fertilizer. Nitrogen in its inorganic form, like we find in a 10-10-10 or 21-0-0 fertilizer bag, does not stay around in the top layers of the soil for very long. Nitrogen is very water soluble, meaning that it can be easily washed away and leaches down into the lower layers of soil relatively quickly. If you apply a large amount of nitrogen before the grass is ready to use it, you have wasted your money.
I understand it is hard for homeowners to hold off on fertilizing their lawns during nice spells of early warm weather and warmer temperatures, but trying to push your turf too much can be a costly mistake. I always try to get folks to hold off until May to fertilize their warm-season turf. A little bit of patience will help your lawn’s health and your wallet.