Hydroseeding on Frozen Ground
When we picture hydroseeding in our mind’s eye, we automatically think about someone out there with a pumper on a sunny spring day, or a balmy fall one. We don’t usually picture someone bundled up in a thick parka, a wool hat and gloves, spraying ground that’s rock-hard and cold as ice, or buried under drifts of white snow.
Many hydroseeding contractors pack their machines away once the weather turns bitter. Some, however, keep on working. Some of them even think that winter is one of the best seasons for applying seed.
Douglas Holmgren is one of those.
He’s president and founder of Turf Blasters, Inc., a hydroseeding company that also does hydro-feeding and sprayon erosion control blankets for residential, commercial and government clients.
He’s also president of the Penn Hills, Pennsylvania-based International Association of Hydroseeding Professionals (IAHP).
“A lot of people think that spring is the best time to seed,” says Holmgren. “But I would challenge that and say that the dormant season is actually better.”
He says that a major misconception on the part of consumers (and many contractors) is that there are only two good “windows,” spring and fall, for seeding, and outside of that, you just can’t do it. “But you can,” he insists. “We get wonderful results from hydroseeding in the heat of July and August, as well as what we call the dormant season,” otherwise known as winter.
By the way, this isn’t some guy in the Sunbelt talking. Holmgren’s business is based in Sioux Falls, South Dakota. Turf Blasters hydroseeds all over the country, and regularly works in our northernmost states, North Dakota, Wisconsin and Minnesota among them.
“What we look for up here is that first frost,” he says. “It’s a good indicator that we’re safe for dormant seeding. Then, unless we get a fluke warm-up, that seed’s not going to germinate until spring. It’ll just lie there, and the snow’ll come down and pack on top of it. Come spring, the slowly melting snow gives a perfect watering to that seed.” The snow, in fact, functions as a natural irrigation system.
There’s another benefit to dormant-season seeding, says Holmgren, and that’s getting a head start on weeds. Seed, especially native seed, will germinate and flourish before weeds appear, so you’re not in competition with them.
The grass will start germinating as soon as the snow starts melting off, when the ground temperature reaches about 60 degrees. “That seed starts popping right away, and gets pretty well established about the same time as the weeds are just starting to germinate,” Holmgren adds.
Tim Grenanco is owner and president of American Hydro Seeding, headquartered in Warren, Michigan. He also does dormant-season seeding for a large number of clients. “We seed right up until we have to winterize our tanker,” he says. “Cold weather could freeze the pipes and cause thousands of dollars in damage to our equipment. But, for the right job, we will come out of ‘retirement.’” For example, one particular chain of retail stores has been a reliable customer. Before the chain can get a certificate of occupancy for a new location, the law requires that the site be hydroseeded. The company “doesn’t care what it costs; it just has to get done,” no matter what time of year it is.
Kevin Huber, owner and president of Challenger Construction Corporation in Clearwater, Kansas, is another contractor who doesn’t find anything odd about hydroseeding in the winter. “A lot of people broadcast seed in the winter. When I was growing up, we just threw fescue seed on top of snow, and waited for the snow to take it down.”
“Once the ground’s frozen, and you know it’s not going to warm up until the spring, I don’t see any reason why you can’t do it. The seed’s not going to germinate in that one day while you’re spraying.”
One caveat: cold-weather seeding does seem to work better with natives. Non-native seed, if it gets a bit warm, has a tendency to say, ‘It’s spring; time to germinate.’ Natives are going to be more likely to lay dormant and not pop up during a warm winter week. “You don’t have to worry about them as much as some of the turf-type grasses,” says Huber.
Seeds can take the cold
Unlike that old, forgotten box of pizza rolls behind the ice cube trays, seed doesn’t suffer from “freezer burn.” As Joe Bilskemper, owner of La Crosse-based Western Wisconsin Hydroseeding has found, seed is very durable. “It’s tough; it’ll lay there over the winter and won’t do anything.”
Holmgren says he doesn’t experience any real seed loss doing winter seeding, but then he does tend to put down a bit more seed for an extra safety margin. For a new lawn installation, instead of the recommended four to six pounds of seed per thousand, he usually puts down 8.3 pounds per thousand.
“That’s our policy,” he says, “year ‘round, regardless of season. It’s a lot cheaper to put down those two extra pounds per thousand than to have to come back and refill the machine, plus pay for labor, insurance, gas—all those things over again—when we could be at a new job, making new money.”
Rainstorms don’t usually wash seed away, either. Grenanco sometimes has to reassure customers of that. “I’ll get calls after storms, people saying, ‘My seed washed away!’ I tell them, ‘It’s underneath the mud; you just can’t see it. Wait six weeks. If it doesn’t grow, I’ll come back out.’ But I usually don’t have to.”
A greater threat to seed is a sudden warm spell. “If the seed starts to establish, and infant grass starts growing, and then gets hit with a hard frost, that’s where we’re going to lose it,” says Holmgren. The justemerged juvenile grass isn’t sturdy enough to support itself through that process.
One problem you won’t have in the winter is dryout, normally a major concern, according to Bilskemper. “You tell people to keep the seed damp once it’s down, but they don’t. Once that seed pops out of the kernel, out of the seed sheath, you can’t let it sit there and bake in the sun; it’s going to dessicate (dry out). But we don’t worry about that in the colder weather so much.” The ‘natural irrigation system’ comes to the rescue, once again.
Don’t neglect prep
Just as with any other type of seeding or sodding, the top inch or two of soil should be roughed up and then leveled and graded before hydroseeding. If the ground is prepped and ready, Holmgren says he can seed all winter long. “Unfortunately, in areas that get this cold, the ground literally freezes to the point where you can’t cup it, till it, disc it or in any way grade it.”
Holmgren says that if more builders knew that they could have dormant-season seeding done, they’d get that ground prepped while they’re doing the exteriors, instead of leaving it for spring. “Then, when the ground freezes, it’ll stay that way; you won’t have to worry about rain or wind erosion, because it’s all frozen in place.”
“We can seed, even in December, when it’s below freezing,” says Bilskemper. “It can work, as long as the soil is loosened. Somebody has to get in there with a drag and break it up a little bit. We need to be able to blast a little of the seed into the soil.”
Special equipment or attachments aren’t needed for winter spraying. “But there are some things you need to be aware of when you’re using the machine in cold, freezing or potentially freezing weather,” cautions Jeff Clouser, general manager of Epic Manufacturing, Greenwood, Delaware. “You’ll need to winterize the machine.”
And, you’ll need to do it every night. Winterizing isn’t just something you’ll do at the end of the fall season, but whenever a seeder has been out in the cold, spraying.
“The key is to drain all of the water out of the machine,” says Clouser. “A lot of contractors will hook up an air line so they can blow out the hoses. I usually recommend putting some windshieldwiper fluid or RV antifreeze down in the pump, so that if any water does collect in the bottom, it’s not going to freeze and split the pump housing.”
A hydroseeder’s brass ball valves are very susceptible to damage from freezing, and these machines usually have three to five of these valves. Clouser recommends “that you open and close those valves three or four times, to get the water out of them.”
Here’s why: each of the ball valves rotates inside a cavity. Water can become trapped in the cavity behind a ball valve and freeze. If you don’t rotate the ball three or four times, you might not clear all the water out of the cavity.
After that, “We recommend leaving that valve halfway open,” Clouser said. “That way, if there’s still a little bit of water in there, it can escape.” Water expands when it freezes, so providing this “escape hatch” lessens the risk of splitting that ball valve.
Obviously, the best thing would be to bed your hydroseeders down every night in a nice, cozy, heated garage. Most contractors don’t have that luxury, however, especially at jobsites.
Hoses can get very rigid in the cold. “Contractors are very ingenious,” Clouser quips. “I’ve seen them take blankets or tarps and tent off the area where the pump and hose reel is with bungee cords. Then, they’ll run a flex line off of the exhaust pipe, and direct the exhaust under the tarps to keep the pump warm, and the hoses loose and pliable and easy to maneuver.” (Just don’t stick your head under the tarp while the engine’s running!) Black rubber hose is less affected by cold temperatures, and remains a bit more pliable. There’s also “clear-braid” hose. This type is made of two clear layers of polyethylene, with a nylon braid woven between.
One advantage of clear-braid is that it’s lighter weight, and seethrough; if you get a clog you can easily spot it. However, it gets very stiff and rigid in the cold. It’s also more prone to degradation by UV rays.
There does come a point where it’s just too cold to spray, Holmgren says, or you risk freezing a hydroseeder’s pipes. “As long as the temperature is above 25 to 27 degrees, I can spray,” he says.
The key is to keep the water flowing. Holmgren knows a little trick to help that: he’ll throw in some extra tackifier to lower the freezing point. Instead of 32 degrees, the chemicals in the tackifier make it so water won’t freeze until the temperature hits 24 degrees. That gives him six degrees of wiggle room before the slurry hardens.
But not all tackifiers are created equal, as Holmgren discovered. A couple of years ago, he decided to try a new formulation. Things looked very good after doing some dormant-season seeding of 45 homes at a new housing development. “When we laid the hydromulch down, it wasn’t freezing outside; we got a nice application of 2,000 pounds per acre.”
Then came the rain—or what began as rain, anyway. As it grew darker and colder, the rain turned to sleet, then snow. Under the downspouts of the houses, water flowed underneath the mats of mulch, and froze.
“The mulch wasn’t bonded to the ground anymore,” said Holmgren. “Water got underneath it, and the mulch floated on top of it.” The water froze into an ice sheet, and the mulch came up off the ground, still bonded to itself, but not to the soil.
This turned the mulch into a flaky crust that could be peeled off like pieces of paper-mache. As the wind picked up, it ripped off big two- to three-foot-wide strips of mulch and seed. Holmgren was forced to go back and respray. He’s still not certain what caused the tackifier to behave like that, but suspects it may have contained an acrylic that reacts badly to cold weather.
The moral of this story is, if you’re going to experiment with something new, don’t do it on a job.
One more tip: Huber suggests that if it’s getting close to winter, and you’re doing a warm-season dormant planting, such as a native grass, it’s a good idea to also put in a cool-season cover crop. He uses sterile wheat grass, an annual rye, or oats.
The purpose of this is twofold— to slow erosion, and to help the soil. “If the cover crop gets killed by the winter, it’s not that big a deal. The warm-season grasses are what you’re really going for.”
Holmgren says that contractors who don’t seed in the winter are missing out on extra revenue. “A lot of guys up here will quit hydroseeding in September. What if they kept going into November? They could have another month’s worth of work.”
Instead of quitting in the fall, Holmgren says, “We just keep working. We know that the next spring, there’s going to be a few sites that we’ll have to touch up.
But I’d rather go touch up those half-dozen or so properties than give up the thirty others that’ll come out fine.”
Seeding frozen ground isn’t only possible; in some situations, it may even be preferable. So think about it…dormant-season dollars are just as green as all the others.