By Bryan Ostlund
Throughout the country, lawns are put to a test of extremes in winter. From freezing temperatures and substantial snowfall to unrelenting rainfall and blustery winds, lawns take significant abuse while lying dormant. As the slow thaw gets underway, it will be important to take stock of how lawns have weathered one of Mother Nature’s harshest seasons, and get prepared to overcome some challenges that often greet lawn care professionals in spring.
Moss, mold, weeds and pests are just a few common problems that landscapers may encounter as they ramp up efforts to prime natural turfgrass in time for the growing season. Such issues will vary in scope and intensity based on a region’s climate, but having a plan of attack ready to deploy will give landscape professionals greater confidence in achieving the desired lush, green result.
Mild, wet winters are a boon to moss
In regions of the country with mild and wet winters, such as the Pacific Northwest, moss has opportunity to thrive. With a growing season that picks up roughly where turfgrass leaves off – from fall to early spring – moss can easily take hold under the right conditions. Shade, poor irrigation, a lack of nutrients, high acidity, mowing too short and thatch build-up can all undermine a healthy lawn and create bare patches ideal for moss to flourish.
Unlike weeds, which have roots and propagate via seeds or rhizomes, moss spreads with the release of spores, making it difficult to use preventative measures such as preemergent herbicides. The best defense is nurturing a dense and healthy lawn year round, with some additional attention in late winter and early spring.
To control shade, thinning out and pruning trees and shrubs while dormant can allow more sunlight to reach the turf. Even shade-tolerant grasses need at least four hours of direct sun to grow well. If thatch is harboring moss, dethatching toward the end of the growing season for moss – by hand or with chemical methods – can give turf a better chance to establish itself. Bare patches should be filled with reseeding, and testing soil samples can provide guidance on whether any pH imbalances or nutrient deficiencies must be remedied.
Snowmelt can reveal festering mold issues
According to Alec Kowalewski from the Oregon State University Extension Service, one issue that is prevalent in colder regions with longer snow coverage is snow mold. “Gray snow mold is a cool weather pathogen that feeds on turfgrass under snow cover,” said Kowalewski. Snow mold is common in cool weather regions of the country, such as the Midwest. Growth of the fungus occurs under a cover of snow when the ground has not yet frozen, and two types – gray and pink – can manifest themselves.
The University of Minnesota Extension Service describes snow mold symptoms as “circular, straw-colored patches when the snow melts in the spring… Grass within the patch often has a matted appearance and colored fungal growth.” Damage may be more unsightly than serious, and affected areas should be raked gently to allow greater airflow that encourages drying. If snow remains on the surface, spreading it out – rather than piling it – can speed melting and air circulation.
Additional remedies from Kowalewski include “repairing the turf with inter-seeding and spring fertilization.” Grasses such as Kentucky bluegrass and fine fescues are not as susceptible to mold. For fertilizer, Kowalewski recommends applying “a fertilizer containing equal parts nitrogen, phosphorus and potassium, such as 16-16-16, to promote turfgrass establishment.”
Not too early to tackle summer weeds
While a dense lawn is the best method of creating a hostile environment for annual weeds, some help may be garnered from the application of preemergence herbicides. According to Grady Miller, Ph.D., at North Carolina State University, “spring lawn care for North Carolina [the transitional zone] is mostly about the late winter application of preemergence herbicides, with or without fertilizer, depending on the grass species.”
Preemergence herbicides are applied before the seeds of summer weeds – such as crabgrass and goosegrass – begin to germinate. The herbicides inhibit growth and can be viable for several weeks. Most treatments are granular and require watering in, as well as a second round of application to maintain effectiveness during the critical germination period.
It is important to note that herbicides can impact root growth on turfgrass, which could create additional issues for struggling lawns. Soil tests can help determine fertilizer and lime application needs to ensure nutrient and acidity levels are appropriate for optimal growth.
Start checking for – and addressing – pests
Various types of pests can compromise an otherwise healthy turf and introduce brown patches to a green expanse. Rather than wait for damage to appear on the surface, experts recommend taking a proactive approach and studying the soil for early indications of problems.
In his transitional zone, Miller suggests checking the soil in spring (and again in fall) for white grubs. Landscapers can cut one-foot-square flaps of sod in several locations, roll them back, and check the soil and roots for grubs. If the average of grubs exceeds five per square foot, then use of a pesticide may be warranted.
In the Northwest, Kowalewski noted that, “European crane fly feed on the turfgrass roots throughout the winter months in coastal areas that receive high levels of winter precipitation and little snow.” Larvae from eggs laid in August feed on turf in late fall and early spring, leaving behind brown and bare spots. Beneficial nematodes or insecticides may be effective in controlling the pest. When damage is present, however, Kowalewski advises to “repair the turfgrass by inter-seeding with a mixture of perennial ryegrass and fine fescue” and follow with an application of fertilizer.
Maintain best lawn care practices year round
Following a well-considered lawn care regimen is the best way to maintain a dense and healthy natural turf that has greater potential to withstand a host of threats. Seed should be selected based on the growing region as well as the amount of sunlight and irrigation anticipated. While spring may not be the optimal time to establish a new lawn, Gregg Munshaw, Ph.D., from the University of Kentucky noted, “If there are thin spots, planting seed once it starts to warm up in early spring can help to fill in the bare areas. Seed should be planted as early in the spring as possible to reduce summer heat stress on immature seedlings.” Seeding early in the year allows grass to develop longer roots in time to reach water deeper in the soil during warm months and fend off annual summer weeds.
For irrigation, Miller recommends watering to a depth of four to six inches and checking soil for moisture to avoid overwatering – if there is enough moisture, a screwdriver should penetrate the soil easily. Depending on the growing region, grass variety and extenuating weather circumstances, annual aerification may prove beneficial by improving drainage and preparing the soil for seed application. Aerification is not always necessary, and Munshaw advises, “Only aerify if soils are compacted or if excessive thatch exists.”
Proper mowing is an essential to proper lawn care. “Once grass begins to grow in the spring it can be mowed a little shorter initially to remove dead material and to improve density,” said Munshaw. “If opting to mow slightly shorter in spring, be sure to raise height prior to the summer heat stress begins.” A good rule of thumb is that no more than a third of the blade height should be cut at once to avoid stressing a lawn. Additionally, spring is the ideal time to get mowers serviced and sharpened to avoid tearing the grass.
Finally, by getting soil samples tested for proper nutrients and acidity levels, lawn care professionals can arm themselves with information critical to determining the best fertilizer composition to ensure a favorable growing surface. Miller recommends applying fertilizer several weeks after grass turns green and following guidelines provided by the manufacturer.
Look for help in overcoming challenges
As winter recedes and landscapers survey the challenges associated with revitalizing lawns for spring and summer, a wealth of information is available through local extension offices. Experts can provide solutions to common problems in specific zones and set caretakers on a path of success. Equipped with information tailored to their growing region and with an understanding of best maintenance practices, lawn care professionals should reap benefits all year long.
Bryan Ostlund is executive director of Grass Seed USA, a national coalition of grass seed farmers and academic turf specialists with a wealth of experience in studying, growing and harvesting grass and grass seed. The coalition seeks to inform and educate residential and commercial customers about the benefits of grass and best practices for responsibly growing and maintaining healthy turf. For more information, visit www.weseedamerica.com or follow @WeSeedAmerica on Facebook and Twitter.