Hydromulching, sometimes referred to as hydroseeding, is a grass planting process. The process is fast, efficient, and
economical. This grass planting process is usually more effective than conventional seeding and certainly more economical
than conventional sodding.
The process begins by mixing mulch, seed, fertilizer, and water in the tank of a hydromulching machine. The mixed material is
then pumped from the tank and sprayed onto the ground. The material is often referred to as a slurry, much like a soupy batch
of green papier-mâché. Once applied to the soil, the material enhances initial growth by providing a microenvironment
beneficial to seed germination.
Hydro-Seeding – A Grass Planting Process
If the area being planted is smooth and manicured, the resulting grass surface will be smooth and manicured. Golf greens are
frequently planted with hydro-mulching resulting in a smooth surface.
Hydromulching material is weed free. However, weed seed is almost always present in the soil, and when the soil gets the
moisture and fertilizer from the planting process, weeds usually appear.
The Mulch Material
Mulch products are usually produced from re-cycled paper or raw wood. Paper mulch products are frequently used where
lower costs are demanded. Wood mulch products are commonly used on sites where good results are expected.
Most wood mulch is produced with special machinery, resulting in a fibrous product. Some wood mulch is made with a
hammer mill process, which results in a product that lacks the erosion controlling effectiveness of “wood fiber”. A very
specific fiber texture is particularly important in achieving an erosion resistant product.
Wood fiber mulch is usually more difficult to mix and pump than paper mulch material. It is a challenge for the producers to
make an effective product that is also easy to mix and pump. Almost all mulches are dyed green for aesthetics. The color also
provides a way to visually determine the thickness of the mulch application on the ground. Mulch products are usually
packaged in 50 or 60 pound bags.
The Value of Mulch
Mulch applied to the soil reduces moisture evaporation from the soil. Grass seed needs soil moisture to germinate and grow.
Moisture must initially come from either irrigation or rainfall. Once the soil has moisture, mulch helps the seed get the most
benefit from that moisture. Poor growth is almost always due to the seed and or the seedlings not getting enough moisture
during certain critical times. Soil moisture is absolutely necessary to grow grass.
A good mulch application also provides erosion resistance. Soil erosion caused by flowing water is always a factor. Mulch
helps hold soil in place and reduces the possibility that the seeds will be washed away, providing a better chance for
establishing a more uniform coverage of grass. Further, when soil erosion is reduced, soil pollution of streams and other
bodies of water bodies is reduced.
Wood mulch, with its fibrous network in the soil, can have significant benefits in reducing or preventing soil erosion. But the
strength of the mulch can be enhanced by using a tackifier. A tackifier is a glue for tying the mulch and soil together.
Hydro-Mulching has a Variety of Uses
New home lawns may be the largest single defined market for hydromulching. Other landscape applications are also
significant. Hydromulching is being used more and more in new golf course construction. Each of these applications is
usually irrigated, and the turf resulting from the application is usually classified as “fine turf”. Sod Quality Results can be
achieved almost every time when appropriate amounts of quality wood mulch and tackifiers are used.
New highway construction always needs new grass planted. Grass is frequently needed on mine sites, and reclamation of mine
sites has increased with the recent concerns for the environment. Utility construction areas frequently need grass after pipe
lines or power lines have been constructed. The list of places for planting grass in these “non turf quality” areas seems to be
endless. Hydroseeding, utilizing less mulch, is frequently used on these large areas to be more economical. Hydroseeding can
work well on these “non-irrigated” areas, if the conditions are not too hot and dry.
Warm and moist conditions promote faster seed germination. Seed bed conditions determine growth rates after germination.
When all the conditions are favorable, most grasses planted with seed will require mowing and have excellent coverage in less
than three weeks. It is possible, under the most ideal conditions, to produce a turf suitable for a football field which can be
ready for play in 60 days. During less favorable circumstances, a good stand of grass can take many months, or even up to a
year, to become established.
Mulch Application Rates
Hot conditions demand more mulch. In the desert southwest, 65 to 80 pounds of wood mulch per 1,000 square feet provides
the best protection during the very hot and dry conditions of summer. However, about 45 pounds per 1,000 square feet does
very well in the spring and fall.
In cooler and wetter conditions, such as in the Pacific Northwest, 35 pounds per 1,000 square feet will usually provide
excellent results. However, as much as 50 pounds per 1,000 square feet will likely be best during July and August in the
It has become apparent in Anchorage, Alaska, that too much mulch tends to reduce the quickness of germination. This is
likely due to the fact that the seed needs warmth, and the sun may not be adequate to heat the soil insulated by the mulch.
The Amount of Mulch in the Tank / The Amount of Mulch Applied on the Ground
Calculating materials for a tank load begins by determining how much mulch can be used in a single tank load. Almost all
mechanically agitated machines can mix and pump from 30 to 35 pounds of wood mulch per 100 gallons of water. A wood
based slurry of 30 to 35 pounds per 100 gallons of water results in a slurry that is not too thick to pump, and it is not too
soupy to apply to hard soils and/or wet soils.
Note: Generally speaking, wood mulch is seldom used in re-circulation mixing machines due to clogging problems. .
As an example, an operator with a 1,000 gallon tank, and with a mechanical agitation system, might choose to use 325 pounds
of wood mulch in each tank load. More than 325 pounds of mulch might be to thick, and less might be too soupy.
Secondly, the operator may choose to apply this 325 pounds of mulch to the ground at the rate of 50 pounds of mulch per
1,000 square feet. The area covered with one tank load could easily be more or less, depending on the nozzle used and the
spraying technique of the applicator. When the operator has made these two choices, then the area to be covered with a tank
load can be calculated. In this case, the area to be covered is 6,500 square feet.
In this example, the area covered with the tank load is calculated by dividing the amount of mulch in the tank by the desired
application rate. Three hundred twenty five pounds (325) of mulch in tank is divided by fifty pounds (50) mulch applied per
1,000 sq ft = coverage of 6.5 thousand square feet.
Once it has been determined that the material in the tank load is going to be applied to 6,500 square feet, then the appropriate
amount of seed and fertilizer for 6,500 square feet can be determined and mixed into each tank load.
After the tank load is prepared with the desired amount of material, the operator must actually apply the tank load of mixed
material onto the desired area. The best way to accomplish this application rate is to measure an area of 6,500 square feet and
mark it off. Then apply the mulch slurry to the measured area until all the slurry has been applied within the measured area.
Experienced applicators can actually apply the materials onto the ground at the desired rate with reasonable accuracy.
Seeding, Sodding, Hydroseeding, or Hydromulching: Advantages and Disadvantages
Seeding – Without the protection of mulch, seeding is less expensive than hydromulching.
HydroSeeding – With little or no mulch, hydromulching can also be very cost effective. Broadcast seeding without mulch, or
hydro-seeding with little or no mulch may be the method of choice due to budget constraints. However, such processes are
always subject to hit-and-miss results.
Sodding – Sodding will provide solid coverage of grass immediately. Also, in many cases, it can be laid during cooler times
of year when seeding cannot be done. However, solid sodding is costly, and the installation is labor intensive. Low cost
sodding usually costs about twice what even premium hydromulching costs. Premium grasses and certified clean sod can
easily cost three times the costs of premium hydromulching using premium grasses.
Premium HydroMulching – Premium hydromulching can provide a full coverage of grass in three to four weeks, depending
on conditions. The cost of premium hydromulching may be more than twice that of thin-mulch hydroseeding. However,
premium hydromulching is considerably less than the costs of solid sodding.
When sod quality results are needed and good irrigation is available, premium hydromulching will provide the desired end
result in three to four weeks for substantially less money than solid sodding.
The Demand for Hydroseeding & Hydromulching is Booming
Almost all construction sites require grassing. The primary question ultimately becomes how good and how reliable must the
grass planting results be. The results needed will determine if lower costs hydroseeding is best, or if the site needs to be
planted with more reliable hydromulching. The biggest problem facing the industry today is that there is no clear definition
separating low cost hydroseeding from premium results hydromulching. This lack of clarity is a problem for everyone.
Many people don’t recognize that there is a significant difference between cheap hydroseeding and premium hydromulching.
The purchaser of the grass is inclined to take the lowest bid, not realizing that he is demanding that the contractor do a cheap
job. The contractor does not necessarily know how to bid a job. He may realize that premium results are needed, but also
knows that price will determine who gets the job in a competitive situation. It is not possible to bid a job at a low price and
provide a premium application.
For Those Buying a Machine for the First Time
It is very important for the buyer of a hydroseeding or hydromulching machine to know these differences in mulching
applications before spending thousands of dollars on a machine. A good hydromulching machine can mix and apply any kind
of mulch, thick or thin. The quantity and quality of mulch in a tank load is far more important than the gallons of water in the
tank. A larger tank and larger engine is no substitute for a machine designed to efficiently mix and pump good mulch materials
at appropriate rates. Re-circulation machines, regardless of size, will not mix even moderately thick mixes, Wood mulch is
never recommended in a jet agitation machine. Re-circulation machines, regardless of size, always take significantly longer to
load and mix. This inefficiency results in significantly slower and more costly operations. The purchase of a cheap
hydroseeding machine can be a disaster for a new contractor intending to enter the business of planting quality grass on new
lawns and fine landscapes.
A new buyer should talk to experienced people in the industry, and should see a mechanical agitation machine operate. Under
no circumstances, should a buyer finalize a machine purchase without first seeing the machine mix and pump premium wood