Root of the problem

We spoke with four experts across the country who talked about what kinds of weed pressures their regions face this season, as well as tips and guidance on how LCOs should approach dealing with these weeds.

WEST: Dr. Alec Kowalewski, assistant professor at Oregon State University and turfgrass specialist

For much of the West, Kowalewski says this season will bring up familiar problems – puncturevines and dandelions. Applying herbicides in the spring and planting the strongest strands of grass possible are tried and true methods to limiting the damage these weeds cause. Puncturevine in particular can actually cause physical harm to people and their belongings, as they produce spikey seeds that will stab into shoes or car tires.

But Kowalewski says perennial weeds like the false and common dandelions are also going to be a problem this season. To combat these, he recommends systematic irrigation. During the summer when temperatures are highest, many states out west receive little rainfall, so he recommends irrigating three or four times a week at a quarter of an inch.

“What happens is if we don’t irrigate in the summertime, the grass dies and then the false dandelion, the common dandelion, particularly will take over the area,” Kowalewski says.

However, crabgrass is increasingly becoming a problem for states out west. In Oregon specifically, Kowalewski divides the state into two environmental zones: the eastern half with higher elevation, little precipitation but cold in the winter; and the western side, which is more moderate during the wintertime but has a lot of rainfall. He says changing temperatures have taken a harsh edge off their winters, so summer annuals have more time to take root and begin growing, especially the farther west you go.

To ward off crabgrass, Kowalewski recommends applying pre-emergence herbicide in the spring.

“Our winters are more moderate. It hardly snows anymore in the western half (of the state), so we have more and more crabgrass emerging,” Kowalewski says.

MIDWEST: Dr. David Gardner, professor of turfgrass science at Ohio State University

While walking his dog in January, Gardner already spotted the growth of some winter annual weeds. He could see them from several feet away, and by the time early spring rolls around, he believes they’ll be even more visible, especially once they flower.

The Midwest is coming off a turbulent season which saw rapid temperature swings all spring. This not only promotes early growth for some of the weeds he’s already stumbled upon this year, but also introduces newcomers like dallisgrass, a perennial tropical grass, and Virginia buttonweed, which has made its way to the Ohio borders.

Gardner says at times, the climate in Ohio wasn’t entirely unlike that in North Carolina. This was due to a “perfect storm” of the variant temperatures. Those weather conditions were also ideal for breaking down any applied pre- or post-emergents, and he says many traditional herbicides or methods like overseeding were unsuccessful last season. He’s doubtful the region will experience that again. Gardner recommends LCOs stick to primary practices to restore density to cool-season grasses. These include responsible application of fertilizer in the spring and following proper mowing practices to prevent causing avoidable damage to the turf.

“There’s a new active ingredient (topramezone) that’s come to market recently that’s made it a lot easier to control crabgrass post-emergence, and even that product last year – whereas it would normally give you 90, 95 percent control – at least in my trials, I was getting 40 percent, 50 percent. It was like a suppression, it wasn’t a control,” Gardner says.

SOUTH: Dr. Rebecca Grubbs, assistant professor at Texas A&M and extension turfgrass specialist

Southern states like Texas have seen extremes in weather this past year. Grubbs says she wouldn’t be surprised if the area sees a regional shift in the weeds that pop up this spring.

“We had turfgrass that sat for days under water,” Grubbs says. “It definitely impacts the health of the turfgrass.” For any region, the climate and weather dictate the weeds that sprout up in the spring.

Southern states experienced a substantial amount of rainfall, and coupled with the flooding, weed species could have easily been carried to different regions. “It’s more important than usual to know the history of the turfgrass you’re treating this spring,” she says.

This spring, Grubbs says to look out for the typical summer annuals that will start to emerge. Carpet weed, spotted spurge and purslane will most likely be identified on the turfgrass and will probably hang around until the late summer.

In the Southwest, be on the lookout for puncture vine wood sorrel and field vine weed. The wood sorrel will sprout up like a clover and feature a violet flower.

She recommends that techs get down a strong pre-emergent to tackle the potential weeds head-on. With the primary turfgrass in the south being Bermuda and St. Augustine, Grubbs says it’s important that lawn care techs be cognizant of what they’re working with.

“You might need to be prepared to do sequential fall applications in the fall,” she says. “Depending on how far south you are, some weeds won’t go dormant.”

NORTHEAST: Dr. Matt Elmore, assistant extension specialist in weed science at Rutgers University

Goosegrass, annual bluegrass, crabgrass and Bermudagrass: They’ve all been problems in the Northeast for a decade, and Elmore says these familiar players will be back in 2019.

With that in mind, he also says these weeds are now encroaching lawns earlier and more frequently. They’re trending upward, but he doesn’t expect things to be dramatically more difficult than last year.

“The biggest thing is that we had lots of rain last year and lots of potential turf loss,” Elmore says. “I think a lot of those trends will continue. I would expect that in some areas where it was tough to control those annual weeds like crabgrass and goosegrass, it might be potentially more prevalent this year just because of all the seed they deposited last year.”

Elmore says adhering to common, popular best practices will be the best way to combat them. He says LCOs who apply a portion of their herbicide in early April and then again six or eight weeks later should see good results this season, though Elmore adds there’s no set timetable for when people should split their applications.

Weeds like false green kyllinga could start to become resistant to other herbicides if you don’t mix it up. Repeatedly coming back with the same herbicide could result in the false green kyllingas becoming resistant.

Elmore says the unpredictability of weather is always going to complicate planning for weed pressures.

“If you could make a big, overarching point about weed control is that the best defense against weeds is going to be a healthy, dense lawn,” Elmore says. “Think about the best cultural practices and fertilizer practices and disease management practices that’s ultimately going to promote a healthy turf.”