Growing Concerns 517: Lawn died over winter, Don't cut tree roots

Late Spring!

Look to the root cause of lawn's failure before starting over

 

Dear Janet,

What do I do with lawn that pretty much died and disappeared over winter? I dug around but didn't find many grubs. There is a hard layer of soil under the sod -- my shovel goes in easily for about two inches then stops dead.

Most of the grass is dead and peels up like rotten brown carpet, but there are tufts of live green. I can't help noticing how regularly spaced the green is, and wonder if the aerating I did last fall is somehow related.

G.B.

Dear G.B.,

You're not alone. A great deal of grass needs replacing this year

I'm glad you checked for grubs before buying grub killer. Although my mail is currently full of questions about grub treatments, what I've seen in my work and travels around the area indicates that, in general, grubs are not to blame. It's disheartening to consider so many people applying insecticide unnecessarily, but worse to think that most are missing the underlying problem and thus wasting their efforts.

The "hard pan" soil you describe is common under grass. It's a consequence of home construction rarely addressed by those who lay sod or spread seed around a new home. A major error, since hard pan will not correct itself no matter how many years pass. Since water and air can penetrate only about an inch, roots grow only that deep. They don't reach even as far as your shovel did, because they rot in the soggy layer right above the hard pan. In such a weak state, a lawn can't survive the repeated droughts we've had. It deteriorates and finally succumbs to diseases or exhaustion.

Live grass around the aerator holes are proof of this -- only where the soil was deeper were plants able to survive. So before you put down new sod or spread seed, do a more serious aeration.

Rent the machine used to install irrigation pipe -- a lawn tractor that draws a knife through the soil. Drive this back and forth across the lawn, first one way and then at right angles, to cross-hatch the whole area with slices spaced eighteen inches apart.

Then spread a layer of compost or that mix of Michigan peat and screened topsoil sold by landscape suppliers as "50-50 mix." Spread as much as you can afford. One cubic yard of either material will cover 300 square feet. Till this in, if the tiller's tines will penetrate. Then rake the area smooth before sodding or seeding.

 

Short reports 

Can I cut the roots of a maple that's ruining my lawn?

Not a good idea. You risk serious harm to the tree and won't even fix the lawn, which is being ruined by shade, not by roots.

Is there hope for a rhododendron that lost its leaves if the twigs are still green inside?

Where the wood under the bark is green and moist, there's hope, if you can also support the shrub through a long recovery.

Can peanut shells be used as mulch or soil amendment?

If it's available in quantity, you like the look and it will eventually decompose, it's a worthwhile mulch. Peanut shells are better for improving soil condition than shredded bark.

Look to your ash trees, Midlanders...

I  saw a great deal of woodpecker damage on ash trees there. That's not  a sure sign but it is one of the symptoms of ash borer infestation.

Look up. If you see piebald areas where woodpeckers picked away at the bark, call in an arborist to go up, remove some bark in those areas and check beneath it for the emerald ash borer's distinctive serpentine galleries -- tracks left from the borer's feeding.

Where you find this definitive sign of the borer, remove the tree quickly before the borers begin to emerge and spread later this month. Don't leave those trees or borers can build up in your area to the huge numbers that were inadvertently allowed here, before we knew what the problem was. If you could see Troy's native wetlands, full of dead ash trees, or drive through some Livonia or Canton neighborhoods that are now devoid of all street trees, you'd understand the urgency to chip those trees into tiny pieces. Then you may keep your other ashes for a while, buying time for replacement plantings to grow.

 

Green thumbs up

to attentive watering of new plants. Let something new wilt even once and its growth is reduced for the whole season. Use a seven day watering system during the critical first weeks. Water on planting day. Wait two days before watering again. Now let three days pass, then four, and so on until there is a seven day interval between one watering and the next. 

 

Green thumbs down

to low expectations in flower planting. Why else would you crowd annuals at 3 or 4 inches apart, even though the tag calls for 8 inch spacing, or more? Crowding insures poor growth, as each plant will have that much less food, water and air. For strong, handsome flowers, space plants as described on their tags, as is done at botanical gardens.

Originally published 5/24/03