Planning on a cool season grass seed this fall? As discussed in our article previous article How to Prepare Your Lawn for Overseeding, there are a few items you will want to know before buying a bag of grass seed to fill in that thin spot. Afterall, a great lawn starts with a turfgrass selection suitable for your site.
When was your last pre-emergent herbicide applied and at what rates?
A pre-emergent is non-selective and kills newly developing roots -- both weeds and turfgrass. These chemicals are cornerstones of all weed control programs and the rate at which each specific active ingredient is applied dictates the length of time it remains active in your soil. These time windows range from 60 days to 6 months generally. Know these details before dropping a hundo on a bag of seed to throw on the lawn.
Do you have irrigation?
If you don't have an underground irrigation system, then a cool season grass is going to be infinitely more difficult to start and maintain, especially through summer. Fescue and Rye both require double the amount of water Bermuda needs. If you can't put down at least 1 inch of water weekly and when needed, you may want to consider another solution. Selecting this turfgrass seed could lead to a headache due to these water needs. For reference, it is generally accepted that an underground irrigation system's output when run for 20 minutes per zone 3 time a week is 0.5 inches of water in total. A typical garden hose fed sprinkler can be as much as 90% less efficient.
Hybrid Seed is Sterile Seed
Seed sold for use in lawns is nearly always a hybrid. Hybrids like turf type tall fescue, perennial ryes, and a large portion of Bermuda cultivars are sterile. Just like Ligers they are beautiful, robust, and unable to produce their own off spring. I say this only to point out that the plant produced from each seed is a one time shot and unlike native Bermuda grass, once it has died from exposure it will not comeback. I should also point out that neither perennial rye nor turf type tall fescue have the ability to produce lateral growth. These guys will not fill in, although they will bulk up as they mature.
Fescue in full sun - the bag says I can!
I know there are plenty of cool season grass' seed bags that say "good for sunny sites" or "full sun and shade tolerant", but that is relevant to the application site. Full sun in Cleveland Ohio is very different than full sun in Tulsa Oklahoma. Chances are its the same bag of seed sold in either location! The truth is any full sun planting site in Northeastern Oklahoma is not suitable for Turf Type Tall Fescue and will only be feasible for Rye until May. (And yes, I will argue this with seed producers and sellers) Professionally, I will only apply Perennial Rye seed to sites that receive 4+ hours of direct sunlight daily (Pictured above: PR overseeded Bermuda I did at my personal home in 2021). For sites receiving full shade or up to 6 hours of dappled sunlight, it's turf type tall fescue. Less than either of those and...well...get a shovel and a truck bed full of rock. More than 6 hours of direct sunlight? Your Bermuda should be growing here. Something other than available sunlight is causing an issue...
Soil Test
Save yourself a whole lot of money by having a true soil test completed. Any soil test you have completed for this purpose should include measurements of the following: Soil pH CEC (Cation Exchange Capacity) Soil Organic Matter Available Phosphorus Exchangeable Potassium Recommendations for nitrogen (N), phosphorus (P), and Potassium (K) necessary for your specific seed genus. Knowing the pH of your soil, the fertility needs, and your basic soil makeup (via CEC and Organic Matter measurements) will go a long way to saving you money by avoiding unnecessary inputs or putting seed into an unviable soil.
I hope these questions spur on deeper thought into what your lawn needs and that it helps you build a GREAT lawn! As always, reach out if I can be of any specific assistance.
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