Give Lawns ‘Muscle’ To Survive Summer 4/22/02

MANHATTAN, Kan. – "Don’t give your lawn a false sense of security" is the advice Kansas State University turfgrass expert Matt Fagerness has now for homeowners.

High Plains residents dragged hoses in and out of storage through winter, as last summer’s dry conditions just kept going. This spring’s rains have yet to bring soil moisture levels back to normal, so homeowners have hauled out sprinklers, along with the mower.

"They may be hurting as much as helping their lawn, particularly if they’re not watering deeply," warned Fagerness, a horticulturist with K-State Research and Extension programs. "Summer is stressful for the region’s most-planted lawn turfs: tall fescue and Kentucky bluegrass. We need to use springtime to train lawns to be survivors, not baby them because their new leaves look so young, lush and tender."

Sidebar:

MANHATTAN, Kan. – Two simple tricks of the trade can make a big difference in how "high-end" a tall fescue or Kentucky bluegrass lawn looks, said Matt Fagerness, Kansas State University Research and Extension horticulturist.

1. Check mower blades before every use. Sharpen after every 10 hours of use – depending on lawn size, about two to three times during the growing season. Millimeter accuracy isn’t necessary, but the blade’s edge should have no visible blemishes and be filed out to a good point.

"Jagged cuts make a lawn look off-color, whitish and sort of sick-looking. Jagged cuts also take longer to heal," Fagerness said. "You wouldn’t believe how much pesticide people waste because their dull mower is making their lawn look like it has an insect or disease problem."

2. Change overall direction from one mowing to the next, while keeping required turns to a minimum. This will even out the turf damage and soil compaction that mower and foot traffic cause.

"Switching directions also helps prevent the strange-looking striped effect you can get because grass blades tend to lean in the direction of mowing," he said.

As turf trainers, he added, homeowners must keep in mind a few common-sense basics on both irrigation and mowing management:

"Yes, the average central High Plains lawn usually needs an average 1 inch of moisture each week. But that’s true only during typical summer weather and for totally average lawns," Fagerness said. "Soil dries out slower when temperatures are cool or the relative humidity is high. Besides, the heavier soil is, the longer it takes to dry out – always."

Soil heaviness can vary within a single lawn, the horticulturist said. Adding to the problem, sprinklers rarely apply water evenly. Rainfall amounts can even differ between front and back yards.

"If you want to know when to irrigate, the better approach is low-tech and very simple," he said. "Don’t water until your lawn starts wilting a bit. Usually, cool-season turfs will take on a darker green or bluegreen cast. And when you walk across a wilting lawn, you’ll tend to leave ghost-like footprints.

"When that happens, irrigate slowly and thoroughly enough to get moisture down 6 inches deep."

Frequent, shallow watering encourages shallow root growth, Fagerness said. When summer comes and the soil surface starts drying out quickly, all of that shallow root system will dry out, too.

"In extreme summers, you can feel like you’re watering all of the time. If you’ve got babied turf, though, you simply may not be able to keep it alive – much less prevent damage," he said.

Fagerness recommends either of two low-tech ways for assessing soil moisture depth.

1. Find a long, thin, metal rod – such as a screwdriver or piece of rebar. Push it into the soil until it won’t go further. Mark ground level, using thumb and forefinger. Pull the rod up. The distance between your fingers and the end of the rod will be the lawn’s depth of soil moisture.

"You need to do this several places, in case your sprinkler is applying water irregularly," he said. 2. Use a shovel to slice straight down into the soil. Push the shovel forward and examine the exposed soil for moisture content. Remove the shovel and close the slice by stepping on it. Repeat the process in other parts of the lawn.

"If you always mow fescue and bluegrass high, you can have an okay-looking and survival-prone lawn. If you always mow low, you can have a thick, but dead lawn," Fagerness said. "Of course, some homeowners believe they must get rid of winter debris in early spring by mowing short. And, in moderation, that can encourage the stand to thicken up – although not as effectively as it will in late fall.

"If they don’t raise their mower by the end of April, however, they’ll be encouraging shallow root growth."

K-State’s turf scientists recommend mowing Kentucky bluegrass no shorter than 2 to 3 inches tall and leaving tall fescue lawns one-half inch taller – 2.5 to 3.5 inches. They also recommend cutting off no more than one-third of grass blade height at any one time.

As a side benefit, longer grass leaves create shade, Fagerness said. That shade keeps soil cooler in summer and interferes with weed seed germination throughout the growing season.

"The One-Third Rule can mean mowing at least once a week during peak growth times, such as May and October," he said. "It isn’t so hard-and-fast that you should cancel travel plans for the sake of your lawn. If you ignore the rule too long or too often, however, you’ll end up with a thin, stemmy stand that depletes the lawn’s root system.

"For times when you must let turf get too tall before mowing, you should gradually bring it back down into recommended range – mow more often, still removing no more than a third each time. Otherwise, your lawn could go into a turf version of shock, one from which it never fully recovers."

The horticulturist believes that even cutting grass when it’s wet is better than letting it grow too tall – if the mower is sharp. [See sidebar.]

"Wet grass takes longer to mow. And there’s no denying that it’s messy," he said. "Wet clippings stick to the mower. They may get deposited as clumps that you have to rake. If you’re not careful, their chlorophyll can stain clothes, sidewalks, garage floor and house siding."

With "dry" lawns and a regular mowing schedule, however, the One-Third Rule allows homeowners to let clippings fall – even without a mulching mower.

"Short or mulched lawn clippings quickly shrivel, filter down and return their organic matter to the soil," Fagerness said.

K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.