Hydroseeding blends
By Tara Beecham
There are few “sure things” in life. In Hollywood, filmmakers can turn to George Clooney to carry a picture. Peanut butter will always taste great with jelly on a sandwich. And when contractors apply seed they need to germinate quickly, they turn to hydroseeding.
The right seed choices, combined with variations of mulch, fertilizer, water, soil amendments, and tackifier for binding, can speed germination and provide swift revegetation.
Creating the hydroseeding mix varies based on the climate, soil conditions, time frame, and budget of each individual project.
“Price-wise, it’s a lot more cost-effective than sod,” says Stephen Thomas, president of Berkley, MA–based Better Lawns and Landscapes and vice president of the International Association of Hydroseeding Professionals (IAHP). “It has a higher success rate than straw seeding.”
Across the nation, hydroseeding jobs are typically priced by the square footage of the area that is to be seeded and ranges from approximately $0.06 to $0.15 per square foot, according to the IAHP.
The hydroseeding mix is blended in a hydraulic tank before the seed is sprayed over a site.
The size of the hydraulic application tank depends on a contractor’s needs, including whether a smaller machine will allow hydroseeding of a larger area and the amount of time available to spray a site, says David Myren, sales manager at Turfmaker Corp., based in Rowlett, TX, which sells a polyacrylimide used in hydroseeding machines as well as the machines themselves. Some machines, Myren explains, are capable of drawing water from another tank, allowing for fewer return trips to the water source, reducing time and labor.
Ultimately, it’s the blend of the materials themselves that will determine if a hydroseeding project is a success. The following examples showcase hydroseeding as applied in a variety of terrains and regions.
Hydroseeding to Protect Natives
New River Gorge National River, a park with 70,000 acres of land along the New River in West Virginia, has steep land areas threatened by slides. In 2001 alone, there were 50 slides in the park. Because of this terrain, hydroseeding can have a limited effect. But the right-of-way areas and the parkland along part of the CSX railroad that stretches from Cincinnati to Virginia do benefit from hydroseeding, says John Perez, a biologist specializing in vegetation at the park. He is based in Glen Jean, WV.
“It should be done. The main purpose is to reduce the encroachment of exotics. As far as soil erosion, there is some benefit,” he says, adding that hydroseeding is beneficial particularly in areas of slopes with a grade of less than 10%, in playgrounds, and in picnic areas. “Hydroseeding reduces the exposure of the soil. You can grow grass on a rock.”
Workers hydroseeding in New River Gorge are required to use native seeds. The hydroseeding that is done at the park is employed to make the most of the germination process.
“Native seed is expensive. Use rates are low. Hydroseeding is great. You can get a lot out of that seed,” says Perez. “We’ll use it on these ball fields, playgrounds—to keep the grass green. We’ll use it in areas where we install waterlines.”
Perez says he follows a checklist and atlas of the flora of West Virginia that is provided by the Department of Natural Resources. Ernst Conservation Seeds, a Meadville, PA–based company that specializes in providing native and naturalized seed, supplies the park’s native seeds.
“We don’t use clovers. Switchgrass is great. We do use annual rye and sterile grains that give you good cover and a good mulch,” says Perez, who notes that the workers are extremely careful about adding any fertilizers or soil amendments to the hydroseeding mix. “You don’t want to encourage exotics. We would do soil tests of the adjoining natural forest or community and try to match those conditions.”
The soil type varies throughout the park, though Perez says the areas of concern are the riparian zones where 65% to 70% of the park’s species are located, in a land area that makes up approximately 2% of the park.
Another project where using native seeds was essential was the Berkley Historical Society’s plan to renovate a historical preservation site located along the Berkley River in Berkley, MA. Thomas volunteered to reseed the entire project area using a specifically required conservation mix, including 70% wood mulch from Turbo Turf, based in Beaver Falls, PA.
“I took it slow, didn’t go too heavy [applying] 1,800 pounds per acre, 70% wood, 30% paper mix,” says Thomas, adding that the soil was “pretty rough” and that everything used to hydroseed the area had to be prevented from leaching into a neighboring watershed. “Things like ECBs [erosion control blankets] and BFMs [bonded fiber matrices] were not an option.”
Big bluestem, switchgrass, little bluestem, Canada wild rye, fox sedge, partridge pea, fringed bromegrass, Pennsylvania smartweed, common milkweed, showy tick-trefoil, New England aster, flat-top aster, and nodding bur-marigold are all seeds that were used in the conservation mix. These seeds are all natives to the New England coast, explains Thomas.
“When I heard them start to look into the project, I immediately thought hydroseeding would be the best bet, not only to get the germination but also to hold in that environment,” he says, noting the erosion that takes place on the edge of a river. “It’s going to be the most stable form of seeding. I broadcast the seed first and then hydroseeded with the 70/30 wood mulch with two layers, one on top of the other, to really build up the erosion control.”
Choosing Hydroseeding Instead of Sod on the Green
At Laurel Canyon Golf Course in Canton, GA, climate and the seeding time frame affected the choice of hydroseeding instead of sod.
“The architect wanted to use Riviera Bermuda. It has a little more cold tolerance and a little bit better recovery time. So he decided to seed this course,” explains Tim Westmoreland, vice president of Mike Westmoreland Contracting Inc., the main contractor for the course. “We’ve got a lot of slopes. Climate-wise, we’re about 40 miles north of Atlanta, but we’re still in a good area for Bermuda during the summer. In the fall and the winter, we used a mixture of bluegrass and hard fescues and added some wildflowers in areas out of play.”
Westmoreland says he had used wood fiber mulch before switching to Centre, AL–based Mulch & Seed Innovations’ cotton-based hydromulch.
“When the wood fiber breaks down, you lose a little nitrogen,” he says. “With a cotton mulch, this seems to hold a little better. It doesn’t seem to lose the nitrogen quite as bad. It seems to bind down and hold pretty good on the slopes.”
If there is an area where a particular type of grass is set to be installed, Westmoreland says, his team might first set the grass down dry by hand before hydromulching over it.
“You need anything you can do to give that grass a head start,” he says, referring to using fertilizers and amendments.
Enter the Wildflowers
Driving through the gateway to Cape Cod, you’ll notice fields of wildflowers along the roadsides, fields that showcase the result of a Massachusetts highway hydroseeding project. Begun in 2005 with a budget of nearly $40 million, the project combined three different blends of special wildflowers in the hydroseeding mix.
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Photo: Polymer Ventures |
| View of the same bank before hydroseeding (top) and 20 days after hydroseeding (bottom) |
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Photo: Polymer Ventures |
“It was called the meadow dry wildflower mix. They wanted a meadow dry and they had wildflower meadow moist, wildflower meadow wet,” says Bob Arello Jr., president of Hydrograss Tech, the company with offices in North Oxford, MA, and Sarasota, FL, that performed the work. Flowers spread over the 20-acre site included common milkweed, smooth astor, New England astor, wild indigo, orange cosmos, silver princess Shasta daisy, Missouri evening primrose, early goldenrod, graygoldenrod, and strawberry clover.
“Any slope work over 4:1 was one-and-a-half times the normal seed rate—roughly about 45 pounds an acre of wildflower seeds,” says Arello, noting that an Apex 4200 Extreme hydroseeding machine was used to spread the seed in the sandy, loamy soil. “We mixed all the materials up; it was two different operations. We seeded first, mulched second. We were able to have the product switched from blow-on to HydroStraw.”
In addition to economic reasons, the company used HydroStraw, produced by Pelletized Straw LLC, based in Manteno, IL, because the site was deemed too windy for blown straw, explains Arello.
“It would be all over the roads,” he says, adding the company didn’t use any fertilizer, hoping to avoid promoting any weeds in the soil. “You don’t want to have competition with the wildflower.”
The material, says Arello, reduced labor costs on the large site. “Because the material is so fine, rates could be reduced, too.” About 2,500 pounds an acre of HydroStraw was applied over approximately 20 acres.
“HydroStraw has preblended polymer in it. We incorporated a polysaccharide binding agent, which is a natural polymer,” says Arello. “Straw created a nice greenhouse effect over the seeds. It promoted the maturation of the wildflower seed. We had phenomenal results. There were so many wildflowers. We had traffic jams with people picking wildflowers on the side of the roads.”
Roadside Seeding Challenges
Steep slopes posed a challenge for workers along a roadway site in Mason, OH. Tim Luers, commercial division manager for Henderson Turf Farm, based in Franklin, OH, says a specified Ohio Department of Transportation seed was used on the June 2007 project. Contracted for work at the site, Luers’s team used micronutrients and Finn HydroStik, produced by Fairfield, OH–based Finn Corp., on the topsoil, which had a reasonable pH.
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Photo: Turfmaker Corp |
| Contractors choose their hydraulic application tanks based on a site’s area and the amount of time available to spray a site. |
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Photo: Reinco |
“We used the additive because we needed to get something growing really quick,” he says. “We used a triple-15 fertilizer as well. The contractor wanted it to come up quick. You’ve got to give it all the nutrients you can so with one or two rains you get as much bang for your buck as you can get.”
Luers used a larger machine on the site to save time. “I get three times as much work done,” he says, referring to working with a larger machine. “You’re being much more efficient. The smaller machine is easier to maneuver in some places. You’ll never find yourself wishing you had a smaller machine.”
Protecting the seed and giving it a chance to germinate is especially important to state transportation departments looking to stay within the boundaries of a budget while required to use slightly more expensive native mixes.
The Louisiana Department of Transportation and Development (DOTD) is not required to use native seeds in its hydroseeding mixes but prefers to use native plant materials when possible, according to Mark Lambert, communications director of the Louisiana DOTD.
“The Louisiana DOTD uses seasonal mixes, with our main emphasis geared toward establishing Bermuda grass during our spring/summer plantings and unhulled Bermuda grass and crimson clover in our winter plantings,” he explains. “Generally, we only use seed combinations in our winter mixes. This would consist of unhulled Bermuda and crimson clover or bald clover.
“The contractors are permitted to include fertilizer and lime in the seeding slurry for application during the hydroseeding operations.”
While somestate departments, such as the Kentucky Transportation Cabinet, do not have hydroseeding programs, others utilize the practice in limited, specialized areas. Hydroseeding is used primarily by the Iowa Department of Transportation (DOT) in urban areas. While the department is encouraged by state code to use natives whenever feasible, it’s not required. Still, the Iowa DOT has made the use of seeding native species in appropriate areas a practice for the past two decades, according to Mark Masteller, chief landscape architect, and Ole Skaar, an agronomist with the department.
“Since our hydroseeding experience is almost solely in urban areas using cool-season turf species, it is very important to provide the proper nutrients and growing conditions to give the seed the best chance to establish and thrive,” says Masteller, based in Ames, IA. “Since we are often working in highly disturbed soils, we always include fertilization. Soil amendments are used only when the existing soils lack the organic matter needed to maintain growth.”
Creeping red fescue, Kentucky bluegrass, and perennial ryegrass are among the seeds used by the Iowa DOT in its urban seed mix.
Occasionally, the Nebraska Department of Roads will use a bonded fiber matrix with either wheat or oats for temporary erosion control measures, according to Ronald Poe, the Lincoln, NE–based highway environmental program manager of the department.
“We have not been using hydroseeding in recent years. Crimped mulch, erosion control blankets, and turf reinforcement mats are our typical products used in construction. We are beginning to look at the feasibility of incorporating hydroseeding into our program,” says Poe. He describes the common seed blends selected by the department. “We are not required to use natives but elect to use primarily natives in our mixes. Our seedings are always a mix of warm- and cool-season natives and a few non-natives. All of our seedings are drilled into the soil with a straw or hay mulch blown over the top and crimped into the soil.”
When slopes are rocky or hazardous for seed application, project managers will allow a seeding contractor for the Montana Department of Transportation to apply seed to the area hydraulically. Otherwise, the department avoids hydroseeding.
“All areas with a slope angle 3:1 and flatter are required to be drill-seeded. All remaining areas that cannot be seeded with seed drills because of limited accessibility or excessive steepness—steeper than 3:1—are dry-broadcast-seeded either with a blower unit or shoulder-harnessed whirlybird equipment,” says Phil Johnson, a Helena-based reclamation specialist with the Montana DOT. “Hydroseeding is not an approved method of seeding on Montana Department of Transportation projects.
“It is our position that hydroseeding only puts a small percentage of the total seed applied in microsites capable of allowing seed germination and/or seedling growth. We have found that dry seeding encourages seed rain into the cracks and crevasses between dirt clods. We strive to create a rough-textured soil surface, which enhances soil moisture retention, shading, and protection from wind shear.”
Individualized seed mixes based on climate and soil conditions are created for each highway construction project. “The selection of species and seeding rates are based on local soil and climatic conditions. Seed mixes are composed almost entirely of species native to North America,” says Johnson. “The use of native seed is not required by law or policy. We feel that the use of native species reduces maintenance costs, lessens the potential for offsite impacts from alien species, and promotes proper stewardship of our lands.”
After areas are dry seeded, he explains, they are hydromulched with a combination of compost and either recycled paper mulch or wood fiber mulch.
“We typically use a 1:3 ratio of mulch to compost. Tackifiers are usually premixed in the mulch product,” says Johnson. “While hydroseeding may be a cheaper method of seeding steep slopes than the combination of dry seeding with a hydromulch dressing, we feel that successful plant establishment is a better measure of cost efficiency and that our two-step approach of dry-seeding and hydromulching gives us the best results.”
Though it can be more difficult to pump, Myren favors using wood mulch during hydroseeding because, in his opinion, “it doesn’t crust over when it dries out,” and he believes it has better erosion control performance than paper mulch.
Fighting a Dry Climate
Hydroseeding was used earlier this year in a battle with climate conditions in a residential development in Kennesaw, GA.
“The inspector wanted a certain percent of coverage on the ground, which, due to the lack of rain, we couldn’t get,” explains Corey Carrol of The Erosion Company based in Woodstock, GA. “We put an additive in. The germination percentage was increased by 40%. The speed of the germination didn’t change as much as the amount of seed that germinated at the same time, compared with a standard slurry mix. It was a fescue/rye mix.”
Polymer Ventures’ PolyGreen 141, a BFM mulch, liquid lime, fertilizer, and tackifierwere added to the hydroseeding mix applied during a severe drought. Carrol says the company used a 19-19-19 fertilizer and a standard vendor’s spec mix. About 6 acres, all slopes, on the 40-acre site were hydroseeded. Watering bands are also in place.
Carrol says he’s used the PolyGreen 141 on several other sites. The product, made with biodegradable ingredients and added to a mulch tank, is used to expedite germination and emergence. He stresses that the amount of germination that occurs when he uses the product compared with the amount of germination when he doesn’t is “amazing. You want every advantage that you can get,” says Carrol.
Though he doesn’t use the practice as often as hydroseeding, Carrol says he’s applied mulch or tackifier hydraulically without seed on certain temporary sites for state transportation department sites. The Iowa DOT has also hydroseeded a bonded fiber matrix product for use as a temporary erosion control solution, according to Masteller and Skaar.
Seed Choice Can Battle a Different Kind of Element
In Brampton, ON, like many northern cities, winter road treatments can take their toll on the landscape. Ken Wray, president of Future Green, a hydroseeding contractor based in Chomberg, ON, describes a site in downtown Brampton where he was hired to hydroseed a boulevard on a city street surrounding a park.
Salt used to treat the roads in the winter had killed the grass, and weeds had taken over. To prevent this from happening again, he explains, some communities will lay asphalt around an area about a half a yard from the curb, but this simply allows salt to slide along the asphalt into the grass. The cost of adding such a strip, says Wray, is about $30,000. Successfully hydroseeding the area with salt-tolerant seed mix costs less than one-quarter of that price.
“We’ve actually solved the problem instead of moving it over,” says Wray. “This is a concept that I’m working on.”
First, the company sprayed to kill the weeds, and then the area was tilled. Gypsum or lime then can be used to flush the soil, washing the salt into the ground. Finally, the area was hydroseeded with a salt-tolerant seed mix, a 10-20-20 fertilizer with slow-release nitrogen, and EcoFlex bonded fiber matrix from New Westminster, BC–based Canfor. EcoFlex was selected because of its strength. The site then was watered to provide the necessary moisture for germination.
Sites like the one in Brampton require particularly careful grass selection. Kentucky bluegrass, commonly included in roadside or urban mixes, is not salt tolerant. The mix used in Brampton is “predominantly a fescue seed blend,” says Wray. “Fescues are more salt tolerant than blue grasses because they have a deeper root system.”
Like a good musician, putting together the right elements for a hydroseeding mix can create harmony. Making the wrong choices has only bolstered criticism of the practice as a whole.
“Hydroseeding over the years has a little more of a black eye [because of] contractors using cheaper material,” says Wray. “In the last 10 years, with bonded fiber matrix coming into the marketplace, we pretty much have guaranteed success if the job is done properly. The bonded fiber matrix is the best thing that’s happened to the industry in recent years.”
Finally, regulation also has encouraged the practice as it moves forward. The growth of hydroseeding’s popularity may be attributed in part to National Pollutant Discharge Elimination System (NPDES) Phase II requirements. Luers believes the NPDES Phase II regulations encourage the practice of hydroseeding.
Thomas elaborates on this point as well. “As we encroach further into wetlands and conservation sites, it’s irresponsible to go forth without some substantial guidelines in place,” he says. “Phase II is a definite challenge, but it’s one we all have to adapt to and adhere to.”
Based in Morgantown, PA, Tara Beecham writes frequently for Erosion Control.
EC - November/December 2007
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