Massachusetts Fertilizer Law: What Homeowners Can Use

Massachusetts caps what you can spread on an established lawn. Under 330 CMR 31.00, the state's Department of Agricultural Resources (MDAR) treats any lawn fertilizer with more than 0.67% available phosphate by weight as a restricted product, and the bag is only legal to apply if a soil test from the last three years shows you actually need phosphorus, or you are seeding, patching, or renovating turf in its first growing season. Grab a classic 10-10-10 off the shelf and spread it on grass that has been there for years, and you are out of compliance.

Most homeowners have no idea. Retailers are supposed to warn you at the shelf, but the sign is easy to miss, and the middle number on the label does most of the legal work for you if you know how to read it.

What Massachusetts fertilizer law actually says

330 CMR 31.00 sets limits on how much, when, and where you can apply plant nutrients to non-agricultural turf and lawns. The turf and lawn provisions took effect June 5, 2015, under the Act Relative to the Regulation of Plant Nutrients (Chapter 262 of the Acts of 2012). MDAR enforces it.

The core rules for a residential lawn:

• Phosphorus-containing fertilizer, defined as anything with more than 0.67% available phosphate by weight (excluding organic compost and natural organic fertilizer), may only be applied when a soil test indicates it is needed, or when the lawn is being established, patched, or renovated.
• No applications between December 1 and March 1.
• No applications to frozen, snow-covered, saturated, or frequently flooded soil.
• No applications within 20 feet of surface waters if you are broadcasting, or within 10 feet if you are using a drop spreader or another targeted method.
• No applications within 100 feet of surface waters used as public drinking water supply, or within a Zone I of a public water supply well.
• Application rates cannot exceed the UMass Extension guidelines for turf.
• Fertilizer that lands on a sidewalk, driveway, or other impervious surface has to be swept back onto the grass.

Cape Cod towns and some other municipalities layer stricter local bylaws on top, particularly around nitrogen. Those go beyond 330 CMR 31.00. The statewide floor is what this article covers.

Who the law applies to

Both homeowners and pros. The application restrictions above do not carve out residential use. If you spread a bag with more than 0.67% phosphate on your own established lawn without a qualifying soil test, you are in the same category as a landscaper doing the same thing.

The one homeowner-only break: record-keeping. Under 330 CMR 31.07, professional applicators must keep detailed application records for three years (name, date, address, soil-test results, product, area, method, rate, total amount). Homeowners on their own lawns do not. That is the extent of the exemption. It does not extend to the phosphorus rule, the date rule, the frozen-ground rule, or the buffer zones.

How to read the NPK label at the store

The middle number on a fertilizer bag is your legal test in Massachusetts. Every bag lists three numbers, N-P-K, showing the percent by weight of nitrogen, available phosphate (P2O5), and soluble potash (K2O). If the middle number is above 0.67, the bag is a Phosphorus-Containing Fertilizer under 330 CMR 31.02 and you cannot legally spread it on an established lawn without a recent soil test showing you need phosphorus. Compost and true natural organic fertilizer are excluded from the definition even if their middle number reads higher.

NPK on the bag	What it means for an established MA lawn
10-10-10 (middle number 10)	Restricted. Not legal without a qualifying soil test or new-lawn use.
24-0-6 (middle number 0)	Legal to apply during the open season. Most modern "lawn food" bags read this way.
20-3-3 (middle number 3)	Restricted. Above the 0.67% threshold.
15-0-15 winterizer	Legal on phosphorus content, but check the date. Late-fall applications must land before Dec 1.
Bag of aged compost	Excluded from the phosphorus rule by definition. Still subject to buffer zones and frozen-ground limits.

Retailers who sell phosphorus-containing fertilizer are required by 330 CMR 31.08 to display it separately from non-phosphorus products and post a sign explaining the restrictions. If you see two shelves and a small state notice on the shelf edge, that is why.

When you can spread, and where you can't

Legal in September does not mean legal in January, and a legal bag does not make a legal spot. The calendar and the ground conditions do more legal work than most homeowners realize, so even a compliant zero-P bag has to land during an allowed window and stay off the wrong surfaces.

Rule	Detail
Calendar blackout	No applications from December 1 through March 1.
Soil conditions	No applications on frozen or snow-covered ground, saturated ground, or ground that floods often.
Broadcast spreader near water	Stay at least 20 feet from surface waters.
Drop or rotary spreader near water	Stay at least 10 feet from surface waters.
Public drinking-water surface	100-foot setback.
Public water-supply well	No applications within Zone I.
Hard surfaces	Sweep any granules off pavement back onto the lawn.

The fall window most homeowners care about opens after Labor Day and shuts December 1. For the practical timing of a fall feeding pass on cool-season grass, the month-by-month lawn care calendar for Massachusetts walks the sequence. This piece is only about what is legally allowed, not what agronomically wins.

The soil-test exemption in plain English

If a soil test taken within the last three years shows that phosphorus is actually needed on your Management Unit (a fancy way of saying the patch of ground you're feeding), you are cleared to apply a phosphorus-containing fertilizer at up to the maintenance rate UMass Extension publishes. The test has to come from the UMass Extension Soil and Plant Nutrient Testing Lab or from a lab using UMass methods. A result is valid for three years and only for the ground it was pulled from.

For most established Massachusetts lawns, the test comes back saying you have plenty of phosphorus already. That is the whole point of the rule. Decades of 10-10-10 built P levels well past what the grass needs, and the surplus washes to Boston Harbor, Cape Cod Bay, and every pond in between.

The other clean exemption path: seeding a brand-new lawn, or patching and renovating a bare spot. Starter fertilizer with phosphorus is allowed during that first growing season without a soil test, because young seedlings actually do use phosphorus to root.

What a legitimate landscaper does on your lawn

A landscaper working under 330 CMR 31.00 on a residential job will do a handful of things you can watch for.

• Ask whether you have a recent soil test on file. If you don't, and they intend to apply a phosphorus-containing product, they should either pull a test or spec a zero-P product.
• Use zero-phosphate or slow-release nitrogen products for routine maintenance feeding.
• Keep an application record with your address, the product, the rate, the date, the size of the area, and the method. That record is a legal obligation for them, not for you.
• Stay off any lawn within 10 or 20 feet of a pond, brook, or lake edge depending on their spreader, and 100 feet from any surface water tagged as public drinking supply.
• Not spread on frozen or saturated turf, and not touch the lawn between December 1 and March 1.

If a lawn-care outfit shows up in early January with a spreader, walk them off the property. If they cannot answer basic questions about the soil test or the product's middle number, that is the same signal. Landscaping around wetland-fringe lots also intersects with the state's Wetlands Protection Act rules for landscaping, which govern the ground you're standing on rather than the bag in your hand.

Coming out of a dry summer, feeding is trickier than it looks; the Massachusetts drought lawn care playbook covers when to hold off and let the grass recover instead. Vetted Massachusetts landscaping contractors who work under the rule are also listed on our directory.

FAQ

Is 10-10-10 illegal in Massachusetts? Not to buy, and not to use on a vegetable garden, in a flower bed, or to establish a new lawn during its first growing season. It is illegal to spread on an established lawn or non-agricultural turf without a soil test from the last three years showing additional phosphorus is needed.

Does the fertilizer law apply to me if I do my own lawn? Yes. Application restrictions apply to homeowners and professionals alike. Only the record-keeping requirement is limited to professional applicators.

Can I fertilize my lawn in February in Massachusetts? No. 330 CMR 31.05 prohibits any application of plant nutrients between December 1 and March 1, and separately prohibits applications on frozen or snow-covered ground.

What is the penalty for violating 330 CMR 31.00? MDAR has statutory enforcement authority and may impose an administrative penalty. In practice, MDAR pursues repeat and commercial violations first. Actual enforcement against a one-time homeowner spread is unusual, but the rule is still the rule, and the retailer notice at the shelf reflects it.

Do I need a soil test if I only use organic compost? Natural organic fertilizer and compost are excluded from the definition of Phosphorus-Containing Fertilizer, so the soil-test trigger does not apply the same way. You still have to stay off frozen or saturated ground, keep within the buffer zones near water, and hold off during the December 1 to March 1 window.

Get a landscaper who does it by the book

If you would rather hand this off, get quotes from Massachusetts landscapers who know the phosphorus rule, the calendar blackout, and the water-buffer setbacks. Tell us the size of your lot and what you want done, and we will match you with local contractors who work under 330 CMR 31.00 the way MDAR wrote it. Start with a free lawn-care estimate.