For different sites and applications, there's more than one "hydroseeding recipe."

By Janis Keating

Ask any seed: Would it prefer being plopped down on dry soil, or would it rather be surrounded in moisture, mulch, and fertilizers? Without hesitation, most seeds would vote for the latter, since those conditions allow for better germination and growth. To give more seeds a chance for success, more erosion control professionals are using a form of hydroseeding to revegetate sites, especially on commercial plots and right-of-ways, where there are usually no onsite property owners who'll give the seeds a periodic sprinkle with a garden hose, as is the case on residential sites.

Although hydroseeding's main purpose is erosion control, different applications and areas of the country require variations in hydroseeding products and procedures.

Different Sites, Different Mixes
Which seed mixes will be used is usually determined by the project's immediate or end use. For quick revegetation, during or after construction, annual grasses are often used, as they will not be the permanent installation. For roadsides and recreational areas, seed choices are made by clients' specifications and the amount of maintenance the area will receive after planting.

Hydrosprout Inc. of Escondido, CA, often recommends a seed mix, but "the majority of the time, a public agency or architect has already written out specs for the site," notes the company's Mike Ritenour. "We see some overlap of seeds in different projects, but for quick post-construction revegetation, you want something to grow quickly without watering, aside from rainwater. This type of job gets a very basic seed mix, one that will establish quickly but not become invasive–an annual grass that'll grow once and not reseed itself."

Photo: TerraNovo/EarthGuard

Hydroseeding the slope after the installation of a watertank.

Wetsel Inc. of Kittaning, PA, used to be called Wetsel Seed Co., so seed manager Mike Steiner knows what he's talking about. "We use what's job-specific, what the architect calls for, and we do custom blending," he says. "We will get what they need in there for their specs. We do a lot of PennDOT [Pennsylvania Department of Transportation] blends. When we make the blends, the Pennsylvania Department of Agriculture has to watch us mix them and test the mixes. They have a certain blend they want–usually tall or short grasses and native wildflower blends."

Sylmar, CA–based Dietz Hydroseeding, which purchases much of its seed from S&S Seeds in Carpinteria, CA, uses "all kinds of different seed mixes," says Ron Dietz, the company's president. "Some are used for vegetation re-establishment after fires, and we often use native seeds for specific sites. We'll use ornamental seeds for residential or business ground covers. Of course, it depends on how far along the site is. After grading they might want permanent vegetation, but if they're not going to build there for a while, we'll use a temporary seed, an inexpensive annual grass, or something more site-specific."

Gary Weems, president Hydroplant in San Marcos, CA, notes, "Each job seed mix is tailored for each job. For temporary mixes, or for erosion control, we will use S&S Seeds' annual grasses. A permanent installation could include native chaparral or buckwheat."

Seasons for Changing the Mix

During California's "erosion control season," October 1 through May 1, exposed soil is forbidden. What happens on a site that's still under construction? "You have to put something down after grading to save the soil," Hydrosprout's Ritenour says. "We can accomplish this without seed–perhaps just an EC blanket, which has been tested even on 1:1 slopes. We can also cover the soil with a mix of liquid glue and hydroseeding wood-fiber mulch; there are minimum mixture rates for the amount of slope and the amount of rainfall. The liquid glue looks like non-fat milk, and it's the texture of heavy cooking oil. When it hits the water it activates and it's awesome how it holds the soil."

As California lacks what much of the country would call "seasonal changes," Dietz doesn't see much seed variation during different seasons. "Maybe a little bit—the changes wouldn't apply so much to seed but to the type of slurry, fiber, or erosion control you're using. If I were planting in September, I'd have more flexibility with seed choices. In January, if you have a storm coming in three days, you might use a heavier-duty product."

Photo: TerraNovo/EarthGuard

Treating slopes with a fiber matrix can preserve soil during winter rains.

"Certain plants will germinate only during certain times of year," Weems points out. "You can put a certain seed variety down at any time, but it might not germinate. Native chaparral germinates in fall in southern California. After few fall rains, the seed sits still during winter, making root system. There's a trend now to go to native grasses, indigenous plants, most of which turn brown in summer. Some landscape architects are trying to protect the environment by choosing native grasses. The choices available for this —native seed' varies region by region. Some times architects will specify site-specific seed—which is tough to use, if there's no seed there. And, although the shrubs are native, recent fires have slowed down the use of chaparral and sagebrush, because they're flammable."

Despite Pennsylvania's weather changes, Steiner doesn't note much seed change: "Seasonally, it depends on what they're using for a nurse or cover crop. Maybe some oats, or annual rye for cover in the spring, they'll put in rye in the fall."

Steep Slopes, Deep Mixtures?

For steep slopes, hydroseeding professionals often use different types of tackifiers or mixtures. On some jobs, Hydrosprout uses bonded fiber matrix (BFM). "This shredded wood fiber is dyed green, so we can see where we sprayed. The color lasts about a week in the sun. BFM forms something similar to a plastic cast, a protective coating over the dirt; we often use this rather than blankets because it's maybe a third of the cost of blankets," Ritenour says. "However, in the past five years, Terra Novo came out with EarthGuard Fiber Matrix, and that product is a fourth of the price of a blanket."

Designed to work directly with soil to maintain its stability by both preserving existing soil structure and flocculating fine sediment dislodged by stormwater or wind, EarthGuard doesn't harden and prevent water from entering the soil.

Photo: S&S Seeds

When wildfires charred this area, S&S Seeds created a mix to revegetate quickly with native plants.

"EarthGuard Fiber Matrix is good for a year, unless we seed it with a temporary seed mix, which adds another year to its life," Ritenour says. "When we make bids for state projects, Caltrans [California Department of Transportation] can't call for a product by brand name, so it asks for —bonded fiber matrix' or —stabilized fiber matrix,' so it can get the lowest bid. Ninety percent of the time, if Caltrans wants BFM, I'll include a quote for EarthGuard Fiber Matrix too, because it works just as well and costs less."

Dietz's use of tackifiers is site-specific. "The time of year factors in, too. After the rainy season, you can use a lighter tackifier. If you have an irrigated site, you can use a different tackifier. Non-irrigated site in mid-rainy season? We'll use yet another type of product. Clients may say, —Give me a basic slurry,' but you really can't do that. What you use depends on the time of year, the soil type, the plant material type, and whether the site is irrigated or not."

"We'll use a wide range of tackifiers, such as guar—similar to the guar gum you see used in food—or bonded fiber matrix, which can put tackifiers, seed, and so on all in one package," Weems says. "Even on non-slopes, if there's wind and water erosion, we will use tackifiers."

Photo: S&S Seeds

This charred hillside above the Barona Creek Golf Course outside San Diego was treated with a fiber matrix.

Wetsel Inc. often uses Second Nature Paper Fiber Mulch or Wood Fiber Blend from Central Fiber of Canton, OH, when hydroseeding. "Asphalt tackifiers were once big—now they're gone," Steiner says. "Now everything's guar-based. As long as the appliers use it at the manufacturers' recommended rate, guar works well."

Another consideration, in addition to seed germination and price, is how a product works with existing equipment. A common complaint about hydraulic mulches relates to the level of contamination. According to Sammy Johnson of Fletcher Feed and Seed in Fletcher, NC, product cleanliness and ease of mixing is key. "Green Choice Premium Paper Hydraulic Mulch is the best I've used," he comments. Made of post-consumer paper fibers by Phoenix Paper Products, the mulch contains no grass seed, allowing users to tailor a seed mix for the project or climate.

Mix Well Over Open Flame

Photo: S&S Seeds

This burned area saw growth of native plants 45 days after being treated.

Photo: S&S Seeds

Customized mixes and site-specific blends thrive in a variety of conditions.

Much erosion control work is performed in areas that have been affected by wildfires, and such cases call for special requirements.

"This fall, we did quite a lot of work for Caltrans along Highway 14, near Santa Clarita. We do a tremendous amount of post-fire seeding," Dietz explains. "Such projects usually entail native seed and a non-irrigated site. You basically want to hold the ash and silt from washing away and let native plants re-establish. There's usually less seed in those projects than there would be in a non-fire revegetation, but fire sites require a heavier, nontoxic tackifier or fiber that will work with the silt to get the seed."

Hydroplant's recent fire revegetation work was performed in southern California. "For a lot of the fire revegetation projects for San Diego we used an S&S native seed mix; a guar gum, Supertack; and then wood fiber," Weems explains. "That was done in the burn areas along roadways, and in some cases around homes. Since the fire department is requiring a further setback from homes for clearing brush, they will end up landscaping, but now they are putting in grasses for temporary use. Anything that will grow from seed we can put down." Native seeds require native conditions. "Some seeds do need scarification from fire or animals, but that's not done commercially too much. You'll put a seed out two years or longer until it gets enough weather to germinate—by that, I mean, nature will beat on it two years until that scarifies it."

In 2004, Hydrosprout worked to control erosion on highway right-of-ways in San Diego County. "Caltrans already had emergency funds set aside for fire revegetation. We performed six highway projects after the fires. We didn't want burned slopes eroding and blowing away a car and driver," Ritenour says. "As many southern California plants won't geminate until they've gone through a fire, Caltrans knew that and specified seed mixes. The San Diego mix was different from the one for Big Bear, so the seeds would germinate quickly when rains came. We made sure to get the EarthGuard Fiber Matrix down to keep the seeds down to germinate. We also worked a golf course project. After the fire, the course, which had been irrigated, was a plot of beautiful grass on black —moonscape.' We revegetated slopes above the course with seed mixes recommended by Aubudon International—native plants that may have disappeared over time."

Photo: S&S Seeds

Areas along a California highway were treated with native plant seeds.

Photo: TerraNovo/EarthGuard

Fiber matrix helped stabilize and revitalize land around a gold course.

Other revegetation efforts were not as successful: "The US Forest Service dropped some seeds and products from a chopper in —inaccessible' areas, one of which was adjacent to a site where we had sprayed. What they put down formed a crust on the surface, and the plants couldn't get through. On the contrary, our EarthGuard sites worked just fine," he adds.

Other Techniques —'In the Mix'

"We'll often hydroseed under EC blankets so plants grow up through them," Dietz explains. "When we do various housing developments, the builder will sod part of it and we will match the sod. However, we don't see a lot of large lawns in California anymore because of the droughts."

Does he use any secret ingredients? "There's really no secret out there; there are many excellent items and seeds on the market," Dietz says. "After 25 years of experience, I've found that planning the project, taking soil tests, and making mixes that are site-specific leads to better success. A —shotgun' approach just won't work. During those 25 years I've also worked with S&S Seeds. They're a great vendor, with a great product line. They make some blends just for us but they also have set-up blends like wildflower blends. We frequently contact them for their input expertise on a specific site." he concludes.

Hydroplant doesn't use EC blankets, "but we put straw over our seed," Weems notes. "We also drill-seed and do land imprinting, which uses a seed box atop a large drum—like a giant waffle machine—which makes an impression in the soil. The seeds fall into those impressions. In dry years, germination takes place in the bottom of the impressions; in wet years seeds germinate in the top part.

Photo: TerraNovo/EarthGuard

Barona Creek Golf Course outside San Diego was treated with a bonded fiber matrix after the wildfires of 2003. Vegetation sprang up quickly.

"We also own a machine that makes stolons out of sod," he continues. "We cut the stolons from the sod on the site, and within minutes of being cut they're in the water in the sprayer. In this process, the stolons rarely go into shock—the leaf material on the stolons are not even wilted. With the 30-year-old process, stolons were usually out of the ground for about 24 hours—you were lucky to get a 30% to 40% —take rate.' This new hydrospraying procedure, especially where it's hot, works much better. We can cover a lot more cubic feet this way, and more cheaply. If watering is done correctly you should get a great take rate with little or no loss at all. We've been using this process on golf courses and school grounds."

Housing projects call for other tactics. "The big thing right now is bonded fiber matrix," Weems explains. "Stormwater people will not let a developer leave disturbed ground—within eight to ten days soil must be covered, or else you can earn a $50,000-per-day fine. We're using a lot of BFM to cover this, which will give the sites cover for up to six months. You can put the seed right into the BFM; if the rains are right they can be growing in no time flat."

Photo: TerraNovo/EarthGuard

Burned areas treated with fiber matrix stand out around the Barona Creek Golf Course outside San Diego.

"Central Fiber's Second Nature Paper Fiber is the cover for our seed; basically, it's like a blanket we can blend in with the seed," Wetsel's Steiner says. "The tackifier holds it through rain or wind, and keeps the seed there. Second Nature Paper Fiber, which is dyed green, also holds in moisture, for better germination. The product is approved by PennDOT, and we've also use it in West Virginia and Virginia. We picked Central Fiber as our supplier because they're close by, in Ohio—and, mainly, because Second Nature works."

"We use blankets and fiber logs, wattles, coconut fiber, and straw. There's not a lot of call for seeded blankets because we can still do it cheaper through hydroseeding, and it's not as easy to specify a seed in a blanket; that would have to be preordered," Ritenour says. "Straw blowing? There's an older technique, but less popular, because of the suspended dust particles. Of course, we try to use rice straw because it's 95% weed-free. We would install these things if ever asked to do so. Most of the time, we use BFM and EarthGuard Fiber Matrix; they're less expensive, labor-wise, because they require a one-step application, where straw is a three-step operation."

Janis Keating is a frequent contributor to Forester Communications publications.

EC - January February 2005