When to Fertilize Lawn: By Region & Grass Type

Determining when to fertilize your lawn areas is fundamental to whether your grass flourishes or is challenged. Overfertilization weakens the roots, leaving the lawn susceptible to drought. Whenever there are shallow roots due to excess nitrogen, the grass cannot access deep moisture in the soil. You should test your soil to determine what nutrients your grass needs.

Many homeowners believe that dumping excess fertilizer can help grow grass faster, and this is a common misconception that costs money and also harms the ecosystem. The nitrogen that is not absorbed will wash away into the storm drains once it rains, causing toxic blue-green algae blooms, which are not only bad for grass but bad for our ecosystems. I've seen lakes become green with blue-green algae in a few weeks after lawns nearby were over-fertilized.

The cost of testing your soil is less than the cost of a bag of high-end fertilizer. A soil analysis will tell you what nutrients your lawn is missing and will eliminate doing it by guesswork. My client saved 30% off of his fertilizer costs last spring after the analysis indicated he was already adding ample phosphorus - which they had been applying randomly before the analysis.

Established grasses have better heat wave resistance than excessively fertilized grass. Fertilize grass only during periods of active growth specific to your grass. Cool season grasses grow in the fall and should be fertilized in the fall; Fertilization for warm-season grasses is best in late spring. Follow the timing to your local environment.

Warm-season grasses -- such as Bermuda -- will require some feed between late spring and the hottest part of summer. Once the soil temperature reaches approximately 65°F, these grasses' root systems will begin to grow in the upper soil layers. This typically occurs in mid-May in the southern states. Cool-season grasses such as Tall Fescue especially benefit from applications of fertilizer in September, increasing the grass's resilience before a frost locks the nutrients in the soil until the spring thaw.

Transition zones, like those in the Texas Panhandle, warrant split applications. At that location, I fertilized Zoysia in late May, after evening temperatures stabilized. You can apply a half-rate in early spring and then a half-rate in early fall. This always prevents summer burnout and is also in accord with local bans on summer phosphorus that are commonplace in drought-prone areas.

The Maryland fertilizer window of March 1 to November 15 is not arbitrary; it serves to protect the Chesapeake Bay from winter runoff. I even informed a few clients closely located in Annapolis, to keep a calendar alert for the stormwater fines. You miss that cutoff date, and the fines are $250 per acre. Another important detail is that I always inform clients to check county extensions before scheduling.

Hybrid grasses disrupt traditional meanings. Zoysia in Missouri needs a lighter application of nitrogen fertilizer in May compared to pure warm-season grasses. Last June, a Zoysia lawn I was maintaining had rust fungus from overfeeding the Zoysia - a reminder that all types of grass - even drought-tolerant - experience problems with nitrogen applications that many predict based on the weather. Apply fertilizer to your grasses' unique DNA, instead of the weather forecast.

Grasses that thrive during cooler seasons, like Kentucky Bluegrass, need their first fertilization done in early spring when the ground begins to thaw. Slow-releasing blends such as 16-4-8 should be applied when the crocuses bloom, which is typically in March in many places in the Midwest. Warm-season varieties like St. Augustine do not require fertilizer until late April or May because its roots are dormant until the soil has warmed to at least 70°F.

The summer drought creates division in our regions. Personally, in Arizona, I have changed clients to a liquid iron supplement in place of granular fertilizers for the duration of water restrictions. The coastal Carolinas? There is a "no-feed" zone in June if we expect heatwaves to break out. The grass will be stressed as it is, and if you feed it during that time, it will simply exude the nutrients, which wastes your product and invites fungal invaders.

Fall nourishes roots, not blades. Sprays in September of 10-10-20 potassium combinations provide the necessary tools to build winter-hardy turf. Just last October, a client of mine in Wyoming had a fescue variety that withstood sustained winds of -15°F, and it was all attributed to our focus on the root zone. If you miss this window of opportunity in the fall, you can expect that spring green-up will be stunted because of shallow frost-heaved roots.

Winters on the southern coasts seem to break all the rules. If Gulf Coast temperatures remain above 50°F, homeowners can put down a 5-5-5 blend in December. I have saved Florida lawns with January applications, but only when soil tests reveal that microbial activity is taking place. I would never fertilize a dormant lawn in the northern states because it is nothing more than putting cash down the storm drains.

Nitrogen deficiencies appear as yellowing leaves on older grass blades, while phosphorus deficiencies will slow root development. When new shoots develop a purple color, low phosphorus is often the cause of the purple color appearing. Potassium deficiencies cause weak cell walls- when the lawn has been mowed the ragged brown edges appear. Last fall, when diagnosing a client's patchy lawn, I determined this was due to potassium starvation, not illness or disease.

Laboratory soil tests cost $15-$30 but will identify micronutrients that the inexpensive DIY strips will miss. One Virginia client saved $120 per year after we learned of excessive magnesium levels with laboratory soil analysis. Home pH kits are fine for quick checks, but I would not rely on them if planning to select then plant grass, as accuracy means the most at that time.

Granular fertilizers do not have time to dissolve before leaching through sandy soils. I suggest the use of polymer-coated nitrogen fertilizers for landscapes in coastal Carolina. Got heavy clay? Use a water-soluble 20-5-10 blend to help reduce crusting. Midwestern loam is the best nutrient-holding soil, so utilize split applications with lighter doses to match its moderate nutrient absorption rate.

Soils in the Pacific Northwest often require lime (calcium carbonate) to ameliorate acidity. Southwest deserts? Applying elemental sulfur will help lower alkaline pH over several months. Last spring, an Ohio client's lawn of 6.8 pH required 50lbs/1,000sq ft of sulfur to be ready for Zoysia to green up properly. Be sure to test every 3 years.

Deep watering encourages roots to search for moisture at depth. During the hotter months, watering 1 inch per week will contribute to a drought-tolerant turf system. Frequent watering with shallow surface sprinkles encourages roots to stay near the surface - I've witnessed turf in July heat simply collapse because the roots were residing in the top half inch of dry soil.

Nitrogen burn occurs in the form of yellow leaf tips with dark green nearly black bases. Drought stress typically makes the entire blades brown. A client once watered heavily on her 'burned' lawn, increasing the concentration of fertilizer salts even more. A reminder: before you do anything, always check to see if there is adequate soil moisture. An easy way to check is to use a screwdriver, which will easily tell you if moisture extends deeper than two inches.

Slow-release fertilizers provide the user 48 hours to activate fertilizer with water; quick-release types require watering within 6 hours. Last May, a neighbor applied a fast-release fertilizer before a rainstorm and I ended up watching $90 worth of nitrogen wash into the street - go with the coated granules if rain is in the forecast.

Salt crusting is an indication of over-fertilization. To leach sodium, apply gypsum at 5 lbs per 100 sq ft, followed by core aeration. In 2022, I revived a salt-damaged lawn in Memphis by applying compost tea weekly - the microbial activity actively breaks down salts faster than plain water.

Rotary spreaders expedite treatment across large lawns; however, they spread granules 8-10 feet next to the rotator and could potentially contaminate the flower beds on the edges of the turf. In tighter spaces, drop spreaders provide a better application and I was able to save a client's azaleas in Boston, MA by switching from a rotary to a drop spreader in their 1,200 sq ft yard. Therefore, consider matching equipment with the size of the turf.

Deflector shields are mandatory within 25 feet of ponds or streams. Maryland's fines start at $500 for an unshielded application adjacent to tributaries of the Chesapeake Bay. Last fall one of my client's koi died due to herbicide overspray. I now recommend using double-sided shields and granular barriers on any property on the water.

In Florida, a new law requires a 10-foot buffer from wetlands for phosphorus utilization. Wisconsin's requirement is a 20-foot setback from the lakes - only in effect between May and October. To keep track of my client's lawns when I fertilize - I mark with spray chalk to alert the homeowner. When I identify the restriction zones I mark them with red boxes because even using organic blends can lead to penalties of $1,000 or more.

Minnesota and Michigan are the hardest hit areas for phosphorus fines. A landscaper lost his license last April after he applied a fertilizer 12-12-12 on established lawns in Detroit. Be sure to check your state phosphorus index; some states will not let you use any product containing phosphorus on any lawn or landscape without proof of soil test deficiency.

Deciding when to feed your lawn requires tuning in to your regional climate, the genetic types of your grass, and seasonal changes. Southern Zoysia exhibits robust growth with feedings in May but forgers in September with nitrogen pushes for the Pacific Northwest's ryegrass. If you disregard one of these components, you are all but guaranteed disadvantaged grass, or worse, falling victim to legalities regarding regulated regions.

Soil testing is not a luxury; it is the roadmap. The client's lawn died the previous year, and although the pH was perfect, the lawn grass was deficient in manganese which is not something standard lawn fertilizers address. Laboratories identify deficiencies in micronutrients that do-it-yourself kits could miss; soil tests can help save you time, money, and heartbreak.

In the next couple of weeks, be sure to test your soil's pH. Reach out to your local extension offices to get a free sample kit. The next step is to compare the soil results to your state's fertilizer laws - for example, Maryland limits nitrogen to .9 lb, while Florida bans phosphorus. Your journey to compliance begins underground.

Soil health, grass species, and local guidelines work together to support robust lawns. Tweak one of the threesomes and momentum halts. Our recommendations are grounded in the practices that test and educate, start with testing and then determine the best timing for the grasses, and leave the local climate to dictate the calendar.