The rules
- Suffolk County: lawn fertilizer is prohibited from November 1 to April 1, with fines up to $1,000.
- New York State: fertilizers containing nitrogen, phosphorus or potassium can't be applied to lawns from December 1 to April 1 statewide. Suffolk's window is stricter.
- Phosphorus: under New York's Nutrient Runoff Law, lawn fertilizer must be phosphorus-free (under 0.67% phosphate) unless you're establishing a new lawn or a soil test shows a need.
A simple Suffolk County schedule
| Timing | What to do |
|---|---|
| April | First light feeding after April 1 |
| Late May to June | Second feeding |
| July to August | Skip or go very light in heat |
| September | Main feeding; best time to overseed |
| October | Final feeding before Nov 1 |
Stay within about 2 to 3 lbs of nitrogen per 1,000 sq ft per year, as Suffolk County recommends.
Ways to need less fertilizer
- Leave grass clippings on the lawn. Suffolk notes they return nutrients to the soil.
- Mow at 3 inches or higher.
- Correct soil pH so grass can use what's already there.
- Water about 1 inch per week, including rain. Overwatering can wash nutrients into groundwater.
Why the rules exist
Long Island drinks from the aquifer under our feet, and nitrogen and phosphorus runoff harms bays and drinking water. Timing applications for when grass can actually use them protects both the lawn and the water.
Keep it off pavement and away from water
New York's Nutrient Runoff Law restricts fertilizer applications within 20 feet of a water body and on paved surfaces. Sweep any granules that land on driveways, walks or streets back onto the lawn so they don't wash into storm drains.
Slow-release vs. quick-release
Slow-release nitrogen feeds grass gradually over weeks and is less likely to leach through Long Island's sandy soil. Quick-release products green up fast but are easier to lose to rain and irrigation. Many lawn programs lean on slow-release sources for that reason.
Don't fertilize right before heavy rain
Heavy rain soon after an application can wash fertilizer off the lawn and into the water. Check the forecast and water in lightly instead.
Lawns that need less
Fine fescue lawns need little feeding, and leaving clippings returns nutrients to the soil. Suffolk County's guidance is to match fertilizer to what the lawn actually needs.
