Growing Concerns 89: Lawn ring spot, moving perennials

Last fall, we saw dead spots in our lawn - dead but for a little patch of green in the center. We took a piece of the bad sod to our garden center and learned it was a disease called frog eye or necrotic ring spot. We were advised to stop fertilizing and think about putting a fungicide on the lawn. We did both, and hoped that would end it but now this week we think we can see it starting again. What now? M.E., Waterford

Few people in Michigan know lawns better than Oakland County MSU Extension Agent Greg Patchan. Here's what he told me about your problem.

Dead rings of brown grass that appear in cool weather are the trademark of necrotic ring spot, a fungus disease. If you look close around the still-green outer edge of these dead spots, that grass is peppered with purplish grass blades.

It's difficult to "medicate" because over-the-counter fungicides aren't very effective against this disease. Even stronger fungicides available to licensed professionals give only partial control. What works better is to change underlying growing conditions that make the lawn susceptible. Once present in the soil, necrotic ring spot fungi don't go away but symptoms may subside as the grass becomes stronger. Such a lawn can literally outgrow this, putting on new root faster than the fungus can kill it.

Bluegrass is likely to succumb to this disease when grown on soil that's rich but compacted - packed down, with little or no air space between soil particles. Chances of disease are worse if the lawn is also stressed by lack of water.

Aerate your lawn every year in spring or fall. Lawn services offer aeration, or you can rent a core aerator to pull plugs of soil from the lawn, leaving small air pits that help bring needed oxygen into the soil.

Switch from quick-release fertilizer to a slow release product - preferably an organic one such as Milorganite, Sustain, or Lawn Restore. These products make nitrogen slowly available, contributing to more balanced growth. Continue to aim for 5-6 pounds of nitrogen per thousand square feet per year.

This may mean an increased bulk of fertilizer, since some slow release products have less nitrogen per bag than other lawn fertilizers. For a 1,000 square foot lawn, annual usage may be 25 pounds of 20-10-10 fertilizer to net 5 pounds of actual nitrogen - that 20 on the label means it has 20% nitrogen, by weight. You'll get the same amount of nitrogen from 83 pounds of a 6-4-4 slow release formula, since 6% of 83 is about 5.

Check soil moisture by digging a pit 4" deep and feeling the soil at the bottom. We had below average rainfall in March, and some soils may be quite dry, contributing to grass stress. If the soil under your lawn feels warm and dry, begin watering. Water lightly - maybe 20 minutes - every day or two through spring and summer if rainfall doesn't provide about 1-1/2" of water each week.

This fall, or even this spring, overseed with grass that's resistant to this disease. Read the ingredients label of the seed mix and use one that includes variety names America, Majesty, Midnight, Monopoly, Able 1 or Adelphi.

I have perennials planted along a privacy fence in my back yard. We are having that fence replaced as soon as the weather permits. What can I do with the plants in the meanwhile, because they have to be moved. There aren't any exotic plants, just daylilies, chickens and hens, lambs ear, violets, phlox, a few seedling trees and a few unknowns. K.W., Westland

Take them out now. Perennials can be moved all year, but results are often best from fall or early spring moves, before they start producing the next season's foliage. We'll see a spurt of leafy growth after our first warm, wet weather. Until then, the plants grow root and wait. Moved when it's cool, they'll root well into new homes and won't produce more leaf than their resized root masses can sustain.

Take as much root as possible - the size of root ball will vary, small for shallow rooted lambs ear, bushel-sized for daylily. Start digging as far out from the crown of the plant as its foliage spread last year. Work inward until you find roots, then dig a circle of that radius around the crown. Pop the whole root mass out of the ground and either transfer it right away to a "holding garden" - maybe a corner of the vegetable garden - or put it into a plastic garbage bag for storage in a cool garage.

Plants "on hold" will be fine until the soil in the root ball gets warm get warm - above 50° or so. At that point they start into top growth and need sunlight. One of my gardening clients has had plants on hold in garbage bags since a well repair disaster in early March forced her to dig them up. We made a mid-April date to repair the soil in that garden and replant, and so far the weather hasn't given us any reason to change the plan!

First published 4/1/95