While September brings with it shorter days, we still have plenty of opportunities to attend to those fall yard and garden chores. Among them is applying fertilizer to lawns. Keep in mind that for the most part, our lawns consist of cool season grasses. In a more typical year, turfgrass growth slows down during dry, hot summer weather. Up until the past few weeks, this summer had seen enough rainfall to keep lawns green and growing.

Turf plants take up nutrients as they grow and these need to be occasionally replenished. September through mid-October is a perfect time to do so as the cooler temperatures stimulate shoot and root growth and hopefully, some gentle fall rains will help the nutrients infiltrate the soil and reach the roots.

So, what kind and how much fertilizer does one need? Of course, the best way to determine that is with a soil test (www.soiltesting.cahnr.uconn.edu) but without a soil test, follow the directions on the fertilizer package. Whether one chooses a natural/organic or a synthetic fertilizer is up to the individual. A 2024 National Lawn Fertilizer Study by Axiom, found that 95% of respondents said it was important to apply fertilizers that are safe for children, pets and the environment. Somewhat ironically, despite safety concerns, 67% have used fertilizers that contain weed killers or insecticides. In most cases, applications of any kind of pesticide, whether it be an herbicide, insecticide or fungicide are not necessary at this time of year.

Most folks who tend lawns or gardens are aware that fertilizer packages come with a guaranteed analysis. These are the 3 numbers on the package, for example 5-10-10. They are always in the same order and always stand for the percent by dry weight of total nitrogen, phosphorus and potassium. Unless you are purchasing a lawn starter fertilizer, which you would use for new seedings and soddings, you will notice that maintenance lawn fertilizers sold in Connecticut have 0 as a middle number, so for instance 18- 0- 4.

This is because of phosphorus legislation passed in 2013. Many people may not be aware that phosphorus is the number one inland freshwater pollutant in the state and when it enters streams, rivers, ponds or lakes, it encourages algae growth that eventually dies and decomposes depleting the oxygen in the water and leading to fish kills. Also, it may encourage the growth of toxic cyanobacteria as well as making the waters undesirable for recreational activities. In a nutshell, the law says that phosphorus should not be applied to an established lawn unless a soil test performed in the past 2 years provides a recommendation for phosphorus.

When applying a lawn fertilizer, either the soil test recommendations or the ones on the package call for approximately 1 pound of nitrogen to be applied for every 1000 square feet of lawn. Two things to check are the size of your lawn and also, the setting on your spreader.

Ideally one would like to apply the fertilizer when the grass is dry but before a light rain. If no rain is predicted, it would be beneficial if the lawn was watered lightly so that fertilizer prills are not sticking to the blades of grass but washed into the soil.

Lawn fertilizers generally are available as either fast or slow release. The nutrients in fast release fertilizers, especially nitrogen, are generally water soluble and readily available to your lawn grasses. Many lawn fertilizers also contain slow release or water insoluble forms of nitrogen. These are typically more expensive but supply nitrogen over longer periods of time. They are less likely to burn and more slowly fertilize plants.

Whichever one you pick; it should be put down by October 15^th. Weather is unpredictable after that, and plants may or may not be able to use the nutrients before colder temperatures prevail and grass growth slows.

This time of year is great for reseeding any bare spots, topdressing with compost if organic matter levels are low, using a mulching mower to incorporate leaves as they fall and for aerating if the soil is compacted. Send your lawn questions to ladybug@uconn.edu or call the UConn Home & Garden Education Center with your queries at (877) 486-6271.