Lawn and Garden

Don’t Bag It, Mulch It

Mulcher Mower Research Project Summary
WVU Extension Service

Lawn care has changed over the last ten years, because of changes in life styles, changes in technology, and changes in government regulations.

The changes in lifestyle are many, but here we will simply say that lawn care is a full-blown hobby for thousands of Americans who undertake it with all of the zeal, gadgets, and gimmicks associated with any hobby.

The biggest change in technology involves the mulcher/recylcer mower. In fact, these mowers overturned many years of extension advice that returning clippings in any form to a lawn would cause thatch buildup and a less desirable lawn.

Government regulations related to lawn waste changed repeatedly during the 1980s and 1990s. Grass clippings have been excluded from the waste stream and landfills in West Virginia since Jan. 1, 1997. In the past, lawn clippings accounted for 5 percent to 8 percent of the material delivered to landfills. This figure was much higher in the spring.

These and other changes prompted the WVU Extension Service (WVU-ES) and extension staff in other states to re-evaluate their recommendations on lawn care.

Thanks to a grant from West Virginia Division of Natural Resources Recycling Grant Fund and the Governor’s Office and a big loan of 18 mowers from Brawley Distributing of Pittsburgh (a TORO Distributor), the WVU-ES was able to evaluate mulcher/recycler mowers.

A review of other recommendations from other states was also undertaken. The overall project was operated under the slogan “Don’t Bag It.”

Extension agents in Cabell, Monongalia, and Ohio counties were involved. The donated mowers were distributed as follows: eight to Cabell, five to Monongalia, and five to Ohio. Cooperators agreed to use the mowers for five years and to assist in some data collection as needed.

Agents gave careful descriptions of the lawns and took samples of soil, thatch, and grass leaves. The soil samples were analyzed for fertility level, pH, and organic matter. Thatch layers were measured, and the leaf samples were analyzed for nutrient elements.

Lawns throughout the study area had very high fertility rates. People have been using excessive amounts of fertilizer to increase yield and color of lawns, with little understanding of how plants grow. WVU-ES faculty believed that homeowners could return essential elements to the soil by using mulching/recycling mowers. They also could mulch leaves, which would reduce the amount of fertilize needed.

The trial lawns were not randomly chosen, the data could not be subjected to rigorous statistical analysis, and data collection was not truly scientific. However, WVU-ES personnel made many observations and drew several conclusions. In Monongalia county the trial was expanded to include lawns of low, medium, and high fertility cut with mulcher mowers and regular mowers; clippings were either left or raked. No significant differences in thatch buildup were found on the lawns studied. Thatch buildup appears to be due to improper fertilizing and watering, rather than to grass clippings being left on the lawn.

More technical research at Penn State University and Ohio State University confirmed WVU’s findings. “Thatch is a layer of living and dead rhizomes, roots, and stems growing between the green layer and the soil,” says Dr. Bill Pound, extension turf specialist at Ohio State University, “not the result of grass clippings.”

Rule of Thumb: Grass clippings do not contribute significantly to thatch accumulation on lawns.

Mowers: Mulching/Recycler versus Conventional

Mulcher/recycler mowers are new technology and not simply a plugged regular lawn mower. They differ from the conventional discharge mower in both deck design and blade design.

Conventional mower blades cut the grass only at the ends of the blades and the blade and deck force the clippings to flow in a horizontally circular direction to the discharge point.


The mulching/recycling mower blade cuts the grass all along the blade at various heights. The blade and deck force the clippings in a vertically circular motion so that the clippings are cut several times before falling down to the lawn under the mower deck. After the multiple cut, these grass clippings are generally 1/4- to 1/2-inch long and easily disappear into the lawn’s surface. They also decompose faster than clippings from a conventional mower.

The WVU study found that mulcher/recycler mowers can handle up to an inch of regrowth easily, even when the grass is wet. More than an inch of regrowth can clog the mowers.

Rule of Thumb: Never remove more than 1/3 of the grass surface at any one time; 3/4-inch to 1 inch of regrowth before mowing is adequate in most cases. Frequent mowing is the key to the “Don’t Bag It” program.

Mulching conversion kits are available for adapting a conventional mower to a mulching/recycling mower. These conversions generally are not as effective as a mower designed specifically for mulching/recycling because the efficiency of the mulching/recycling action depends upon both the design of the blade and the shape of the deck. To mulch/recycle grass clippings requires a little more power than the conventional cut; therefore, a converted mower may be underpowered.

Shortcomings of mulching mowers are that they are heavier and more expensive than traditional mowers. They also are not well suited for people who mow on a schedule rather than when the grass needs mowing.

When properly used, however, the mulcher/recycler mowers can save time because clippings do not have to be raked or bagged.

All involved were surprised at the homeowner’s acceptance of the aesthetics of the lawns on which the mulcher/recycler mowers were used. The finely chopped grass clippings quickly disappeared into the standing grass.

General Lawn Care

Grass Clipping Disposal

If you have decided that you’re “not going to put grass clippings into plastic bags for disposal with household wastes,” you’ve made a wise economic and environmental choice. Grass clippings are a valuable resource for your lawn and landscape.

Disposing of your grass clippings on your property can be accomplished in two ways:

1. Collect clippings to compost or use as a mulch. Many mowers are equipped with grass catchers so clippings can be moved from the lawn to your composter or sites requiring mulch.

Government regulations excluding yard waste from landfills have led to much interest in backyard composting. Composting is simply a way of speeding up natural decay of organic material. Because grass clippings have a relatively low carbon to nitrogen ratio, they are best composted with such higher carbon wastes as fall leaves. If composted alone, the grass clippings heat very rapidly and require frequent turning to keep them from developing undesirable odors.

Dried grass clippings may be used as a mulch. Allow them to dry in place before raking. If clippings are collected in a catcher, spread out the pile and allow it to dry before applying as a mulch. Piles of fresh clippings tend to form a mat that impedes water movement. Clippings are quite fine compared to other mulches; therefore, a thinner layer will provide weed control. Dried grass mulches tend to decompose rapidly and need to be replenished frequently. Do not use clippings from lawns treated with herbicides as mulches. For additional information on composting, obtain a copy of WVU Extension Service publication 864, Composting Yard Waste.

Rule of Thumb: Because grass clippings are 75 percent to 85 percent water they decompose readily. Dried they amount to little material.

2. Leave clippings on your lawn. Many styles of mowers have side or rear discharge, which spreads the clippings over your lawn. The 1- to 2-inch grass clippings from these mowers generally are visible on the lawn for several days after mowing. This problem led to the development of the mulching/recycling mower.

Fertility Levels

Lawn care, at the local level, is not too complicated. Grass grows in response to soil type and fertility, soil exposure, type of plants involved, and the management plan used. WVU recommends doing a soil test to determine fertility and lime requirements. Although several elements are needed for plant growth, five essential ingredients must be added from time to time. They are calcium and magnesium in the form of lime, and nitrogen, phosphorus, and potash, in the form of fertilizer. Soil analysis every three to five years is the only practical way of monitoring these five critical elements and pH. Once the lawn is limed as recommended, desirable pH will remain for three to five years. The chart below shows the primary levels for major elements.


Relative Availability or Sufficiency Levels

major lawn nutrients

Soil structure is perhaps as important as fertility. Where natural soils are involved, we know a lot about how deep the soil is, and how much water it can absorb in a 24-hour period. Backfills, graded soils, and disturbed soils are a big question mark. The WVU soil testing laboratory can determine only the organic matter level. Generally, levels of 3 percent to 5 percent are deemed adequate.

Exposure plays a big role in how plants grow in response to wind and weather. People need to realize that a lawn on a slope facing south and getting full sun, will not respond the same as a lawn on an east-facing slope that gets only the morning sun. Management decisions will be needed to solve slope-related questions and problems.

Fertility levels are important in lawns. Once the correct amount of lime is used to get the desirable pH, fertilizer becomes an issue. Generally, fertilizers contain three elements: nitrogen (N), phosphorus (P2O5), and potassium (K20). The three numbers on the bag, bottle, or container of fertilizer show the percentage of N, P2O5, and K20 (in that order) the product contains.

Once phosphorus and potassium get to high or very high levels, as shown by a WVU soil test, adding more of these nutrients will not result in increased grass growth. Species may change with more phosphorus and potassium, which encourage clover and weeds. Nitrogen is the fertilizer element that makes everything bigger, taller, and greener. That is why the highest number (indicating nitrogen) usually is the first of the three numbers listed on the fertilizer container.

Lawn grass varieties are numerous. There are varieties that are fine and coarse; those that are tolerant to heat, cold, drought, and wet conditions; and those that are resistant to insects and diseases.

Once these basics have been determined, management plans can be designed to cover fertilization, watering, mowing, and controlling insects and diseases.

Experts will argue about the timing of fertilizer applications. Most people today, however, feel that all three elements need to be added during the fall. Fall fertilization gives plants a chance to recover and grow when the weather is cooler and when there is less competition from trees, weeds, insects, fungi and diseases.

Experts generally agree that nitrogen added during September and October will give the lawn the dark blue-green color that the neighbor’s lawn always seems to have.

Fertilizer Application

Fine fescue, perennial rye and turf-type tall fescue: Apply 2 to 4 lbs of nitrogen per 1,000 sq. ft. Annually, with two-thirds to three quarters of the fertilizer being applied between Labor Day and Thanksgiving Day in 2 to 3 equal applications and the remaining in middle to late May.

Kentucky bluegrass: Apply 4 lbs of nitrogen per 1,000 sq. ft. annually on the same schedule as described above.

A new time-release nitrogen fertilizer is changing the number of applications needed per year. Newer fertilizers applied through the end of the garden hose also are changing application times. These newer products are more user friendly, but they are much more expensive than the normal sources of fertilizer.

Watering of lawns is constantly discussed in West Virginia. Cost is a major factor in watering, as about 1/2-gallon of water is needed to deeply wet a square foot of soil, amounting to about 25,000 gallons of water per acre. Water will indeed keep grass growing throughout the growing season, but under very hot, humid conditions water also increases fungi that can damage grass leaves. Extension recommends no watering during the heat of the summer. Instead the cold-season grasses should be allowed to go dormant for a few weeks or months.

If water is added, it should be added weekly during the early morning hours or in the early evening to reduce fungus problems. The 1/2-gallon of water per square foot needed will amount to 1 inch of water in a rain gauge or container. Within reason, the water needs to be added slowly to avoid compacting the soil and to prevent runoff.

More frequent watering with less water will not wet the soil to a sufficient depth, resulting in a shallow root system that will suffer during periods of dry, hot, windy weather.

Mowing itself can make the difference between a healthy vigorous lawn and a poor lawn. As people turn away from chemicals, mowing techniques can also greatly reduce the need for weed control on a lawn adequate fertility.

Regardless of the type of mower used, mowing height is perhaps the most important aspect of lawn care. The higher the grass variety can be maintained, the healthier the grass will be. Extremes can cause problems, but a mowing height of two to three inches provides more shade and reduces soil temperature, is more wind resistant, reduces water loss, and provides barriers that prevent weed seeds from germinating. Once a mowing height has been established, a remow height should be set. The general rule of thumb of 3/4-inch to 1 inch of regrowth before mowing is adequate in most cases. Too little regrowth between mowings results in wasted time and energy. Too much regrowth results in longer mowing times and more damage to the grass. Sharp blades provide a better cut surface, allows for faster cutting, and requires less energy from the mowing units.

Mowing Patterns

Homeowners usually ignore mowing patterns, but golf courses dazzle the public with their elaborate designs. Changing the mowing pattern 3 to 4 times a year gives a lawn a fresher appearance. The wheels of the lawnmower find new soil, and the rotary mower pushes the grass sideways at a different place.

The appearance and the quality of the lawn can be improved by changing the direction of mowing every 3 to 4 weeks. Options are illustrated below…

mowing patterns

Other options may be better for your specific lawns.

It is important to keep a lawn mower well maintained and to mow at the correct height. Dull blades will damage the grass plant, and incomplete cutting will occur, particularly with the mulcher/recycler.

All mowers are expensive. Good maintenance will extend the life of a mower and significantly reduce lawn maintenance costs.

Just which lawn plan is best is up to the homeowner. Homeowners need to decide what type of lawn they want and then seek out the advice needed to produce that lawn. West Virginians are fortunate in that the climate allows for a great deal of diversity.

Summary and Conclusions

Some benefits of mulching/recycling mowers:

  • Proper mowing, watering, and fertilization practices develop a lawn that needs fewer chemicals to control weeds, insects, and diseases. This is particularly true when you have established a lawn with improved grass varieties. Reduced chemical use contributes to a more balanced natural environment.
  • Nutrient elements are returned to the soil. Grass clippings add to the soil organic matter and nutrient element pools. Literally hundreds of pounds of grass produced from a single lawn can be returned to the soil surface rather than placed in a public landfill.
  • Less mowing time is required, and you do not have to bag or rake grass clippings.

Some disadvantages of mulching/recycling mowers:

  • Frequent mowing of the lawn is needed because only 3/4-inch to 1 inch of new growth is removed per mowing.
  • Grass and leaves need to be dry for the mower to work properly.
  • The majority of these mowers may be heavier and cost more to buy than conventional mowers.

The WVU study is continuing, and other states are examining long-term results of using mulcher/recycler mowers.

The WVU Extension Offices in each of the 55 counties can be the first stop for obtaining lawn care information.