Spring Planting: Strategies for Erosion Control Vary Greatly

Jan. 1, 2001

Choosing an effective spring planting strategy to prevent soil erosion can be like trying to find the right pair of new shoes. If you don’t know what you need, you’re likely to pick something that doesn’t fit. Worse, you’ll have a hard time getting where you want to go.

Imagine walking onto a muddy spring field and getting shoes that don’t fit stuck in the muck. Two things will be obvious: (1) You picked the wrong footwear, and (2) it’s probably not a good time to plant.

One solution involves consulting the experts. Soil scientist Brent Hallock, a researcher and professor at California Polytechnic State University, San Luis Obispo, says it’s virtually impossible to generalize an approach to spring planting, particularly when protection from soil erosion is the goal. When and how to plant seeds, for example, will depend on the climate and terrain, as well as the more esoteric measures of soil composition and microbiology.

Considering how people in the western United States might approach such a strategy, Hallock wonders, “Why are you trying to get springtime erosion control in an area such as California, where precipitation drops off drastically in the warmer seasons?” Hallock does feel that spring planting in California is possible, even with a dearth of rain in the warm months, especially when one’s goal includes soil stabilization and water quality. Certainly rainfall and runoff are not problems to contend with, as in many other regions of the US. Hallock knows that getting plants up before summer aids against wind erosion and soil compaction, and in some cases provides aesthetic value.

Hallock advises having a clear understanding of the variables that can enter into an effective plan and exploring those variables up front. This holds true for all spring planting strategies across the US. While each region offers particular challenges, Hallock notes that California challenges soil scientists and seeding contractors to a high degree. They must create general plans for an area famous for its geologic and climatic diversity.

For example, the notoriously dry inland valley region of California presents a set of different problems from those found in the Sierras to the east and in the coastal mountain ranges to the west. Hallock says that even a region as small as San Luis Obispo County, with its Mediterranean climate and native chaparral species, gives reason to think carefully through any erosion control plan.

Studies for spring planting must include distinctive weather patterns, geology, soil conditions, aspect (north, south, east, west), slope, elevation, and seed source, especially if there’s pressure from municipal and regional government agencies to use native plants.

Species Selection Strategies

Norm Poppe of Applewood Seed Company, based in Arvada, CO, warns that the complexity of choosing what to plant in the spring makes it risky to generalize. For example, in small geographical regions, such as Colorado’s mountainous areas, elevation plays a significant role in what to plant.

Additionally, some customers have no idea what they need, Poppe says. Others, including the Bureau of Land Management, the Colorado Department of Transportation, and the forestry department, “will specify very clearly what they want. Often they know more than we do.”

When talking with customers about spring planting strategies, Poppe helps them analyze their goals, consider their expectations, and review all of the variables. Then he assists in selecting the appropriate species, choosing “the one that looks like it will work the best.”

To further illustrate the complexity of deciding what approach to take, Poppe gives seed selection as merely one aspect of an erosion control plan with numerous variables to consider. For example, different species of seed with their different traits will largely determine when the seed should be planted. Much depends on how each variety handles weather and soil conditions. A hard seed variety, such as Texas bluebonnet, which may prove more effective in cooler climates, requires a longer germination period, including the breaking-down action of freezing and thawing, water and gravel, and microbes and enzymes, to work on the seed coat and activate germination. “You can see there are a number of variables with just one species of seed,” he remarks.

Additionally, the ratio of seed that germinates right away as opposed to seed that takes longer is a factor. When do you want germination? An ideal might be 75% now and 25% later. Reaching that ideal depends in part on how quickly the warm and arid seasons arrive.

Clients looking for a ground cover before summer must consider the amount of rainfall expected through the warmer season, which can vary wildly depending on where in the US the customer lives.

Timing Is Everything

In the Intermountain region, which includes parts of Colorado, Utah, Nevada, Wyoming, and Idaho, earlier is better for spring planting, advises Doug Vance of Granite Seed Company in Lehi, UT. This area gets dry very quickly, he says. To have any impact, planting must be early, preferably by March or late winter. Seed should be in place by April before the spring showers, which are usually short in duration. After that, it’s simply too dry for any plants to thrive. “You have to get the plants up and growing before summer,” he recommends.

Vance adds that wheatgrasses and fescues are most commonly used. It depends on the particular site and whether the soil is sandy or full of clay. Because dormant planting is probably best, most planting occurs in the fall.

Mark Mustoe is a rancher with 1,200 ac. in eastern Washington. He notes that because there can be little to no precipitation by June, it’s a common practice among landowners and the Forest Service to seed on the snow just before it melts. In these kinds of dry regions, melting snow acts much like a mulch. The snow helps get the seed in good contact with the soil, he says.

Mustoe serves as a consultant with Landmark Seed, which offers turf and native and forage grasses. He says the seed needs to be out there and growing by June for it to have any impact on disturbed areas. By the end of spring, “the plant needs to be in its two- to three-leaf stage to do any good.” Melting snow helps move the process along.

Mustoe and many farmers and ranchers throughout the area use hand-seeders to spread cool-season grasses. It’s an old practice. “My grandpa did it,” he adds. For larger areas, an aircraft can spread the seed over the snow.

Seeding and erosion control contractor Kelly Ellis of Stephen B. Ellis Company in Utah – an area also typically drier as the season warms up – learned the benefits of seeding in the snow almost by accident. Late one November, while hydroseeding and hydromulching cuts and fills on a slope without topsoil, the snow began to fall. Ellis kept seeding. He thought that as long as the seed and mulch kept feeding cleanly, no harm could be done.

Next spring, Ellis visited the site, an elevation between 8,000 and 9,000 ft. “We could see that the mulch was still green and in place, and those were huge slopes.”

Ellis also seeded during a late snowstorm in the spring while working the north side of the Great Salt Lake. Again the snow kept falling and he kept seeding to good effect.

He later observed that the melting snow helped wash the seed into the ground. The snow is actually a great mulch and serves as a kind of blanket for the seed. Additionally, the snow has its own built-in irrigation system when things start to warm up, Ellis notes.

In the drier climates, there doesn’t seem to be much risk of the seed floating away, he adds. “I’m not a scientist, but the snow seems to melt from the bottom and doesn’t wash the seed away. I have yet to see the seed wash away.”

One downside is that in deeper, wetter snow, it’s not known what’s underneath, making it difficult to know where to seed.

Ellis believes it would be a great experiment to seed between snow storms and observe how well cool-season grasses fare.

Moisture and Frosting in the Northeast

In the northeastern US, heavy moisture and unpredictable frosts are likely to be the critical factors in a spring planting strategy, points out Julie Marcus of New England Wetland Plants Inc. Based in Amherst, MA, the company specializes in native plants for ecological restoration, erosion control products, and native seed mixes.

Marcus and her husband Mickey sell eight mixes, mostly warm-season grasses, to customers in the northeast where there’s a huge problem with summer precipitation. Rainfall can take out whole slopes in a single downpour, Julie says.

And with strict legislation protecting against soil erosion, especially at construction sites where particulates are not allowed to leave, it’s vital for landscapers and builders to take advantage of the brief, six-week window between the first thaw and the onset of summer.

While rainfall is nearly always a given in the warmer months, it’s erratic. “The weather here can be pretty extreme,” Marcus remarks, adding that it’s not unusual for temperatures to fluctuate 100º in a 24-hour period. Because spring frosting poses a problem, Mickey notes, the fall is usually preferable for seeding.

New England Wetland Plants offers two erosion control/restoration mixes: one for detention basins and moist sites and another for dry sites. The first mix contains 16 species of mostly native grasses and wildflowers, including Tioga deertongue, creeping red fescue, switchgrass, Virginia wild rye, and fowl bluegrass. Best results come with spring seeding, although summer and fall seeding can be successful when combined with a light mulching of weedfree straw to conserve moisture. The mix works to colonize generally moist, recently disturbed sites where quick growth of vegetation is desired to stabilize soil surface. The plants, found mostly in the northeastern states, can tolerate infrequent downpours, but not constant flooding. The dry mix contains seven species, including creeping red fescue, annual rye grass, timothy, white clover, little bluestem, red top, and side-oats grama grass. It is useful for road cuts, pipelines, detention basin slopes, and areas undergoing ecological restoration.

Both mixes can be spread by hydroseeding, mechanical spreader, and by hand on smaller sites.

Because precipitation can be erratic and heavy, Mickey prefers the use of erosion control blankets to keep new vegetation from washing away. “We work with a lot of ecologically sensitive sites,” he says. The company’s overall species list, unique to the area, is unusual and not often found in other areas of the country. Even with a specific focus on a region such as the Northeast, it’s difficult to offer a generic solution to spring planting strategies, Mickey remarks, “because each job is so different.”

“Finding solutions to the challenges of specific jobs is what we love to talk about,” comments Calvin Ernst, general partner with Ernst Conservation Seeds in Meadville, PA. The company specializes in the restoration of hard-to-seed sites, including landfills, roadside embankments, and wetlands.

Opinions vary greatly on what is the best approach for spring planting, Ernst says. “You will often hear conflicting information about what is the best way. It’s not that one method is wrong and another is right but that there are many applications that might work.”

Along with weather and location, it is important to consider the type of job to be performed. “The present trends and demands for construction, for example, are going to be very different from those of agriculture or, say, wetland restoration,” Ernst adds.

His customers, which include national parks, highway departments, conservation groups, and contractors, come with jobs ranging in scale from very small to very large. He finds that often these are people with little background or knowledge of erosion control issues.

Ernst says that in the northeastern US and in some parts of Canada, the poorest months to plant are July and August. This poses a challenge for road crews and construction companies, which tend to have their busiest and most productive months following the spring thaw.

Ernst explains that a road crew might be ready to pave in August, the worst month to put down seed to protect newly constructed embankments. Nonetheless, some strategies exist for clients seeking erosion control methods during the worst planting season. Hydroseeding and protecting the seed with a mulch, hydromulch, or erosion control blanket are among the most common practices in the Northeast and usually work well with small- to medium-size jobs.

Economics plays another significant role in determining what works best. While hydroseeding may work well along some roadways, steep hills, and other sites accessible to trucks, Ernst feels it would not prove economical for larger sites where, for example, fire might have destroyed thousands of acres. Large burned-out areas are often reseeded by aircraft.

Suitable Soil Temperatures for Spring Planting

For farmers and in areas where the ground is likely to remain frozen for longer periods of time, waiting for suitable soil temperatures is another factor to weigh.

“For a seed to germinate it must have good contact with the soil and be placed in a favorable soil environment,” write agricultural climatologists Steven J. Meyer and Allen L. Dutcher in a paper titled “Soil Temperatures and Spring Planting Dates” (1998, www.ianr.unl.edu/pubs/fieldcrops/g1362.htm). “A good soil environment is one that has suitable soil temperature, adequate soil moisture, good aeration, and for certain seeds, light. Conditions necessary for germination depend on the species and variety of seed being planted. Alone, none of these factors guarantee germination; rather it is the interaction of these factors that affects seed germination.”

For germination of spring-planted crops, they continue, “soil temperature becomes an important factor since it affects both the capacity for and rate of germination.”

They provide a table with dates in which soil temperatures in Nebraska reach a threshold value. The ideal dates vary according to a number of factors, including soil type, water content, and spring snow cover.

Each spring planting strategy, with erosion control as its objective, will vary according to a number of critical factors. These can and should be studied in minute detail with the help of experts in the field, whether suppliers of appropriate species of seed and erosion control technologies or researchers such as Cal Poly’s Hallock. Hallock is in the middle of a three-year study with Caltrans to identify plants that will take in soil for each of the 12 districts maintained by the state highway division. Each district is different and requires its own special blend of techniques and species to stabilize the soil, he says.

One goal of the research program – the Vegetation Establishment Maintenance Study – involves getting plants up in 30 days and still having them on the site three years later. Two plants under consideration are yarrow and California brome. The researchers are also looking at lupine, buckwheat, and California sage.

Hallock says Caltrans, though not mandated, is under pressure to use perennial natives, which require cycles to be successful. A good way to go, he adds, is to mix natives with adapted plants – those that have adapted themselves to a condition exclusive to the area.

By the end of the three-year study, Hallock plans to have full lists of species capable of both thriving in each of the 12 districts and protecting against erosion. “We’ll come up with recommendations and guidelines for each district,” he says.

Much is still not known – particularly what will survive. Experts continue to develop their understanding of how to protect against soil erosion and attempt to come up with the most appropriate solutions specific to the challenges.

If you’re considering a spring planting strategy to protect against soil erosion, study how to approach the challenge. Talk to the experts. Think of your challenge as finding the right shoe for the purpose you have in mind – aesthetics, utility, comfort, or all of these – and if the shoe fits, wear it.