“Annual and perennial ryegrass provide the most rapid germination, five to seven days, and grow quite rapidly,” says Dave Nelson, the Salem, OR–based executive secretary of the Oregon Tall Fescue Commission and administrator of both the Oregon Tall Fescue Commission and the Oregon Fine Fescue Commission. “Annual ryegrass grows most rapidly of the two. Fine fescue and tall fescue provide long-term cover and are quite drought tolerant once established. They will go dormant during periods of high heat and dryness, but will recover when it cools down and they get some moisture. Care must be taken to not shade out these species with too much ryegrass in the early stages of growth since they are not as aggressive as the ryegrasses.”

Bruce Berlin, manager of erosion control products and product testing at S&S Seeds, a company based in Carpinteria, CA, that specializes in providing native grass species, explains that the best revegetation decision is based on your objective.

“As a seed company we work with planners and architects to help design a specific seed mix to meet their objectives,” he says. “It may be that they just need a quick-germinating erosion control mix to hold their slopes over the rainy season. In that case, we would use primarily the quicker-establishing, deep fibrous-rooted annuals that come up and get established quickly.

“In other cases, the objectives may include the temporary erosion control requirement but also have self-sustaining but permanent and native ornamental elements as part of the objectives, in which case we would use a balanced combination of quick erosion control components that would still yield to the slower-establishing, deep-rooted, and self-sustaining natives.”

Many people request permanent seed mixes to blend into the native hillsides that surround a project, explains Berlin. “By being a seed company that knows the soil types, the climates, the topography, and most importantly the plant material that is native to the particular region,” he says, “we can effectively match specific plant palettes to specific geographic regions and specific projects.”

Going native with seed selection can hold various meanings for project managers. “The ‘what constitutes a native’ debate sometimes comes up, but revegetation practitioners and native plant groups in California generally refer to The Jepson Manual, an authoritative vegetative flora book that gives great taxonomic detail on the flora in our state. Native versus naturalized is sometimes debated,” says Berlin, adding that the company often receives “natives only” requests.

PHOTO: ILLINOIS DOT

 For more than three decades, S&S Seeds has performed onsite seed collections. The company employs field-trained seed collectors who travel to a specific site, collect seed at the point it is most ripe, clean it, and then “test it, store it, and give it to the project managers when they are ready to seed it,” explains Berlin. Such collections require between 12 and 18 months of lead-time and a contract.

In Hawaii, there is a more specific definition of a native grass. “A native Hawaiian plant is defined as one that got to Hawaii initially via a natural process, or, more specifically, one of the three “Ws”: wind or wind currents; wing—migratory birds; or wave—ocean currents,” says Chris Dacus, a landscape architect with the Hawaii Department of Transportation (HDOT), adding that native plants are encouraged by law. “At HDOT, our approach is becoming more and more to use native plants if they’re the best plant for the situation.   

“Since Hawaii is a unique state, it’s our intent to use native plants wherever possible to have a Hawaii sense of place. Native plants include indigenous and Polynesian-introduced plants. Polynesian plants are considered plants that were brought by Polynesian ocean voyagers. There are limitations, though, because of limited availability of native species statewide; thus, if a highway project is using native species, usually the plants are grown for the project.”

PHOTO: PELLETIZED STRAW

Traditionally Bermuda grass has been used for highway projects, says Dacus, but HDOT is interested in using native grass seed as well.

“Wildflower mixes on the mainland raise concerns about invasive species, as most of these mixes contain at least one invasive plant to Hawaii,” he says. “HDOT, in conjunction with a federal grant from FHWA [the Federal Highway Administration], is starting a three-year research project to develop native grass mixes and hydroseeding techniques for native grasses. It’s our hope that in the future we hydroseed native grasses, but we are aware that the general public may or may not appreciate the aesthetics of native grasses, so a good public relations effort will be needed.”

The decision to use native grasses for erosion control can bring with it additional responsibilities. In North Carolina, selecting a native species can depend on availability.“Native grasses are used in riparian buffer zones or other environmentally sensitive areas that are impacted by our projects,” says David Harris of the Roadside Environmental Unit of the North Carolina Department of Transportation’s (NCDOT’s) division of highways, based in Raleigh. “There are many companies now that provide all types of native grasses, but we are required by law to have all seed tested by NCDA [North Carolina Department of Agriculture] before it can be used on NCDOT rights of way. This limits the availability of seed for our needs.

“Native grasses present another set of problems,” he adds. “Natives are very slow to establish, and they do not typically provide an expectable turf to minimize erosion. Native grasses, depending on the time of year that they are seeded, can take up to two years to establish, which forces NCDOT to rely on multiple cover crops before the natives can establish.”

“It’s vastly more common to use commercially available seeds,” says Philip Spackman, manager of Grassworks Southeast, an erosion control grassing company based in Atlanta that uses Pennington Seed Co. of Madison, GA, as one of its vendors. For example, says Spackman, the fescue imported from Missouri and the Bermuda grass from Arizona both prosper in the Georgia soil.

Successful planting for erosion control can also be affected by topography. “Fescue and lespedeza are blended for slopes,” says Spackman, adding that they are favored for their deep roots. They are then replaced with permanent seeds when the growing season returns.

Whatever seed mix you choose, ensuring seed quality can affect a project’s success.

Oregon produces approximately 65% of the world’s supply of grass seeds used in temperate climates worldwide.“After the seed has been harvested and cleaned in one of the 400 seed-cleaning plants in Oregon, it must pass both a germination test and a purity examination before it can be offered for sale,” says Nelson. “A representative sample is drawn from a ‘lot’ of seed—a lot is usually 50,000 pounds—and sent to a registered seed-testing laboratory.

“The majority of the seed is tested at Oregon State University Seed Laboratory. Each bag or box of seed contains a label that shows the test results. It also has a lot number on it and can be traced back to the exact field on which it was produced.”

Georgia is one example of a state where all seed sold must have a tag that lists seed purity, germination rate, and the weed content based on test results.“The presence of a certified tag on a seed lot is a guarantee of its trueness to type from a genetic standpoint but gives no indication of seed quality in terms of germination or purity,” says Mike Krysiak, president of Encap, a Green Bay, WI–based company that has been involved in rebuilding ecosystems damaged by forest fires. “When it comes to germination, specific rules and procedures have been established for determining the germination percentages of various turfgrass species.”

“Basically, we look at the construction schedule and the temperature. You are at the mercy of the weather to an extent,” explains George Ryan, an implementation engineer at the Illinois Department of Transportation  (ILDOT) based in Peoria. ILDOT typically uses temporary oats for the initial seeding because of their characteristically quick growth and good coverage.

This process worked well during a recent 8.5-mile, $461 million project where roadsides and large interchanges required seeding through downtown and East Peoria areas. Conditions were ripe for good germination with nice rains following the seeding process.

“Typically, you’re seeding in late fall, early winter,” says Ryan. “[The Peoria project] includes about seven interchanges, so there were very large areas to be seeded. Usually, the job is going to be done toward the tail end of the construction season.”

ILDOT uses seven different main seeding-type mixtures. Where there are slopes that need to be seeded for erosion control but that it is unlikely to mow, the department uses a mix of lower grass that includes little bluestem, sideoats grama, wild rye, prairie dropseed, annual ryegrass, oats, and perennial ryegrass, says Ryan. Usually, seed mixes are applied through hydroseeding, he explains, and “then wherever we did temporary seeding, we’ll hand-broadcast [seed] to get it out after the soil has been worked.”

Harsh weather can affect revegetation decisions. “Construction schedules always take priority over seeding schedules. We formulate our seed mixes accordingly. We also do a lot of dormant seeding, and our new specifications on seeding provide for seeding over the top of snow,” says Leo Holm, section director of the Minnesota Department of Transportation (MNDOT) Office of Environmental Sciences based in St. Paul. “We either plant a permanent seed mixture which has both permanent and temporary species in it, or we seed a temporary mix and then till the area up and seed the permanent species. Most of the time, we seed the permanent mixture. We have several permanent mixtures, which can be native mixes, turf mixes, wet-area mixes, or an introduced-species grassy mix.”

This is similar to plantings taking place in the far-southern United States. “Unfortunately, not all projects are ready to revegetate at the optimum grass-planting date,” says Barrie Cogburn, director of landscape and enhancements in the Texas Department of Transportation (TXDOT) Design Division based in Austin. “It’s hard to hold up a $35 million interchange because it’s not the right time of year to plant grass. Expecting seed to germinate in 110-degree weather is very difficult. If the project is ready for revegetation outside of the recommended planting dates, we add a temporary mix to hold until the more permanent grasses can take hold.”

Poor soil conditions are often a challenge for revegetation projects, but agencies that cooperate with each other can find viable solutions. “We use native mixes around all our stormwater ponds and wetland mitigation sites. We use native mixtures for about half of our seedings on general roadsides,” says Holm. ”We have defined ‘native’ as being from Minnesota and about 50 miles into the surrounding states and Canada. The Minnesota Crop Improvement Association is working with us on a yellow-tag program for native seed sources. They inspect growers’ fields and also seed conditioning and blending plants.”

NCDOT works with NCDA when selecting seed mixes for establishing vegetation on a project.  “We do use cover crops to help during the winter months as well as the long hot summer months when establishment of vegetation is the most difficult,” says Harris. “The department is required by law to seed and mulch any area that is left untouched for more than 21 days. In many cases we have reduced that to 10 days. Typically, we select warm-season grasses for the eastern part of the state and cool-season grasses for the western part of the state. The eastern part of the state has sand with low organic matter that presents nutrient problems and water-retention problems. In the mountains, we have problems with steep terrain and rocky soil that lends itself to accelerated erosion.”

TXDOT has a specified permanent seed mix for each region within the state. “Within our 25 highway districts, we have even more specific seed mixes,” says Cogburn. The TXDOT vegetation management staff sometimes works in conjunction with the Natural Resources Conservation Service for seed mix solutions.

MNDOT uses a slow-release nitrogen fertilizer, compost, and organic fertilizers with its seedlings. “We have not been doing much with seed coatings,” says Holm. “We used some mycorrhizae but did not see a huge difference in stand density after about six months. We always use inoculant with the legumes and usually at a two-times application rate.”

NCDOT, which relies largely on hydroseeding machines for seed application, is investigating a new way to approach seeding mixed with amendments. “We are also experimenting with a company that applies a blanket of compost from municipal yardwaste that has the seed injected into it,” explains Harris. “We have had good results with this technique, but the cost is prohibitive.”

PHOTO: TXDOT

Compost is the main weapon TXDOT uses to combat poor soil conditions, following a drill-seeding process. “Quite simply, the addition of compost amends existing soil to grow grass faster and better,” says Cogburn. “Better established vegetation means less erosion, and this translates to less headaches, and money saved. Compost is used to amend the existing soil, and the native grass is planted with a no-till drill. We have long believed that the best seed choices are those that are native. Natives can handle the tough demands of the right of way best. They are more hardy and can live without the pampering that’s needed for some of the more high-maintenance grasses.”

Various ecosystems coexist in Colorado, making revegetation projects challenging for the Colorado Department of Transportation (CDOT). “Snowfall/rainfall can run from 30 annual inches to 8 annual inches,” explains Susie Smith, a landscape architect for CDOT based in Denver. “We have high-altitude mountains to low-altitude sand dunes, from forested foothills, to high-plains deserts, and everything in between.”

The I-70 corridor project was located west of the Eisenhower Tunnel, the highest vehicular tunnel in the world, where steep slopes at more than 11,000 feet were successfully revegetated through the use of various techniques. The tunnel is located an estimated 60 miles west of Denver.

“First and foremost was soil preparation. The use of organics and inoculates was key,” says Smith. “Project timing was used in the narrow window between winter snow and spring rains and fall and winter snow. Second seedings and erosion blankets were also used as successful techniques. In this instance, hydroseeding was the only option, with operators suspended by ropes to keep from tumbling down steep slopes. Using tackifiers and ensuring the hydroseeding and mulching were separate operations. All of these techniques and a commitment from the contractor and CDOT staff made this project a success.”

During the process, the project engineer worked extensively with the organization to stabilize the site within the necessary timeline. Unfortunately, this is not always the case.

“At this point in CDOT culture, seeding is the last operation prior to the contractor completing the job and getting paid. CDOT is trying to alter that by making seeding affect schedule and budget, which are both important to the contractor,” explains Smith. “This will be a large culture shift that is taking support from upper management and the contractor associations.”

Rainy conditions can hamper even the best efforts to grow grass, but not having the opportunity to prepare the soil on a project you must seed, says Spackman, is the most challenging situation for grass contractors. “We try to use a mixed-grade fertilizer, liquid lime in our hydroseeding applications, and agricultural limestone for tractor-planted applications,” says Spackman. “Where I live, the dirt is blood red.”

While there are many methods of application, Nelson describes hydroseeding as the most popular. “This method can also use pre-germinated seed for quicker establishment,” he notes. “The seed is soaked for several days to ‘get it started,’ then seeded.”

PHOTO: S&S SEEDS

Beginning in 1997, the Wuhan Soil and Water Conservation Service and 13 regional universities in China worked with the Oregon Tall Fescue Commission testing a variety of grass species during a 4,000-mile erosion control project above the Three Gorges Dam at Yichang, China. This revegetation project was especially challenging.

“If they are unsuccessful, the dam will fill with silt in the next 10 years. They’re racing against time,” says Nelson. “They used both engineering and mechanical processes. They are working with a variety of different species to minimize erosion. They are using ryegrass, tall fescue, bent grass, and fine fescue.”

Seed application was one of several challenges faced in revegetating part of Spanish Fork Canyon following a six-day blaze. During the summer of 2004, the Red Bull Fire tore through 1,836 acres of Uinta National Forest near Provo, UT.

Encap was among the leadership team involved in rehabilitation treatments to revegetate burned slopes. “For large forest fire products, typical application is aerial via helicopter or fixed wing,” says the company’s Krysiak. “Smaller projects use standard drop or rotary spreaders that can be pulled behind equipment or pushed by hand. In forest fire restoration projects, it is all native plant species. The team formed to determine the revegetation plan brings in a local expert to determine the mixture required for the actual location being treated.”

A seeding bucket dropped native seed species and PAM-12 soil granules from a helicopter for the Uinta National Forest project at a rate of 46 pounds of seed and 600 pounds of PAM-12 per acre. Three thousand pounds of straw per acre were applied by hay bale bombing as mulch for the seed. In the nine months of field observation that followed, it was determined that PAM-12 outperformed straw in terms of seed establishment, soil hydrophobicity, and erosion control.

Gilpin explained that HydroStraw, a hydroseeding mulch manufactured by Manteno, IL–based erosion control product company Pelletized Straw, has a carbon-to-nitrogen ratio that allows it to biodegrade more quickly than paper or wood mulch.

“It provided a seed-friendly mulch environment, which seems to promote prompt germination and good early plant growth,” says Gilpin. “The contractor can put more in their tanks so they can deliver more pounds of mulching material in every load and thus every day.         

 “On some restoration sites, greater success has been realized by allowing the first flush of weed seed to germinate. These weeds are then sprayed off, and they plant the slower-developing target plants. On larger-scale construction projects, the sites are typically subsoils, so the best results are achieved when they deliver slow-release nutrients, mycorrhizal inoculants, and seed that is well protected by substantial mulch.”

Wildlife Habitat Nursery in Princeton, ID, primarily sells plugs of wetland plants grown in forestry-like containers—approximately a quarter-million of them annually. Denny Dawes, Wildlife Habitat’s owner, says the company always uses native plants, including rushes, bulrushes, willow, and cottonwoods. Wilbur-Ellis Co., based in Spokane, WA, supplies chemicals the company uses in its nursery, including a Peters Professional 20-20-20 General Purpose water-soluble fertilizer. Wildlife Habitat also uses a starter fertilizer and a finisher, explains Dawes.

As techniques in the landscaping business have made transplanting larger plants easier, using larger plugs has become more common.

“Primarily we grow in a 10-inch container. The tops vary in height,” says Dawes, explaining that it’s common now for people to order even 1-gallon containers of herbaceous plants. “That was something that was pretty rare.”

Some areas of the country need to focus on soil pH when applying amendments, such as Hawaii, where Dacus says most projects use a gypsum amendment like Airtol because of the soil’s high pH level.

“Compost and AM120 Mycorrhizal, along with Humate and organic fertilizers like Biosol, are all good tools and amendments when trying to establish native plants from seed,” recommends Berlin.

“Grassy swales and vegetated buffer strips are pretty hot right now,” he says. “People want to slow the water down, allow the sediment and any pollutants to settle out, and then let the water percolate back into the ground rather than flush it all into the storm drain system and out to sea.”

Spackman in Georgia has noticed an increased use of common Bermuda grass because of its drought tolerance. “The fescues here struggle in the heat,” he says. “[Bermuda grass] thrives in the heat.”

Seed choice is moving toward specialization, targeting the best plant for a site rather than a quick selection. “Trends that we see are being more site-specific, using native wetland species for ponds and wetlands, turf species for turf areas, less use of an introduced all-encompassing seed mixture,” says Holm. “We also see more yellow-tag native species being asked for.”

While revegetation is always entered into with some amount of risk, improving your odds of successful plantings doesn’t have to be a gamble. With carefully considered choices at the project’s outset, you can establish vegetation that provides the planned landscape with years of strength and splendor.