Kansas Ag Connection - Crabgrass Making its Annual Summer Appearance

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Crabgrass Making its Annual Summer Appearance
Kansas Ag Connection - 08/14/2020

Kansas State University horticulture expert Ward Upham says that patches of crabgrass showing up in homeowner's lawns are a sign of work ahead.

By the time the weedy plant shows up in the summer, it's a bit too late for homeowners to use their best means of control, which is to apply a preventative herbicide in the spring, killing the seed as it germinates.

"Crabgrass is an annual that must come up from seed each year, and the seed must have light in order to germinate," Upham said. "If a lawn is thick enough that sunlight does not reach the soil, crabgrass won't germinate."

Upham added that there is some hope for control if homeowners did not apply crabgrass preventer last spring.

"Some of the herbicides that will kill crabgrass include Ortho Weed-B-Gon Max +Crabgrass Control, Fertilome Weed-Out with Crabgrass Control, Monterey Crab-E-Rad and BioAdvanced Lawn Weed and Crabgrass Killer," he said. "Each contains quinclorac for crabgrass control, and other active ingredients that control broadleaf weeds. Quinclorac not only controls crabgrass but also has good activity on foxtail and certain broadleaf plants, such as field bindweed, black medic and clover."

Those who choose not to apply more herbicide to their lawn can be comforted in knowing that crabgrass starts declining by the middle of August.

"That's about the time that such cool-season grasses as tall fescue and Kentucky bluegrass start to come out of their summer doldrums," Upham said. "By the first of September, the crabgrass will be less noticeable. So, a small infestation is best ignored. Crabgrass is a warm-season annual and will be killed by the first frost."

Hot temps call for watering trees, fruit

Upham advised homeowners to water trees and fruit to give them an extra boost as temperatures top 90 degrees Fahrenheit.

"If you have fruit plants such as trees, vines and canes, check the soil moisture at the roots," he said. "Insert a pointed metal or wood probe or even a long screwdriver to check the depth of watering. Push the rod into the soil with the goal of reaching eight to 12 inches."

"If you cannot reach the recommended depth, the plants should be irrigated to prevent drooping and promote fruit enlargement.

Upham said fruit plants can be watered with sprinklers, soaker hose, drip irrigation or even a small trickle of water running from the hose for a few hours. Strawberries, which have a shallow root system, and newly-planted fruit tress in sandy soils may need to be watered more often.

For landscape trees, Upham recommends a perforated soaking hose circling the tree several times to even out the amount of water applied. Soil should be wet at least 12 inches deep. New trees may not have enough of a root system to absorb enough water, so water weekly and apply mulch at the base.

Upham and his colleagues in K-State's Department of Horticulture and Natural Resources produce a weekly Horticulture Newsletter with tips for maintaining gardens and home landscapes. The newsletter is available to view online or can be delivered by email each week.

Interested persons can also send their garden- and yard-related questions to Upham at wupham@ksu.edu, or contact your local K-State Research and Extension office.

Brand names appearing in this article are for product identification purposes only and are not intended as an endorsement of any specific product.

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