From Joseph Rimelspach & Todd Hicks / The Ohio State University – Dept. of Plant Pathology
Many lawns are coming out of winter in poor condition. A number of different factors are involved. The thin or dead turf will pose challenges this season especially with achieving acceptable weed control. The following are some observations seen in Ohio this spring.
Much of the damage seems to be associated with the very wet conditions last fall and winter followed by extensive “heaving” of the turf plants. Frost heaving occurs when wide temperature fluctuations, with repeated cycles of freezing and thawing, cause the water in the soil to expand and contract. This can cause the plant crowns to become elevated. If roots are exposed to cold temperatures and drying winds there can be decline or death of the plants. Lawns with this condition may benefit from light rolling. If there are large bare areas seeding and renovation may be helpful.
Areas in shady lawns seem to be the worst. In some samples/lawns the grass affected was Poa trivialis (rough bluegrass) this is a shallow rooted turfgrass and often found in shaded sites. This grass would peel back or is loose and not rooted.
In other cases there is bare soil exposed, with no grass present. One main cause was damage to the lawn last summer and fall from disease(s). One particular disease that was epidemic last year throughout Ohio was Gray Leaf Spot, caused by the fungus (Magnaporthe oryzae). This disease kills perennial ryegrass. Where the disease was active last summer and fall the grass was completely killed and decayed and left bare areas in lawns.
The sudden shift from hot summer weather on October 10, 2018 to wet cold conditions the rest of the fall, did not allow for successful seeding and renovation of lawns or lawn recovery from the intense and stressful summer. The majority of lawns in Ohio are composed of cool-season grasses (bluegrass, ryegrass, fine fescue and tall fescue) these grow best in mild autumn and spring weather. Since the weather quickly changed from being too hot to grow these grasses to too cold, there was little time for the cool-season grasses to recover and fill in before winter.
Winter conditions caused many Kentucky bluegrasses to have severe browning of the leaves. In most cases the crowns of the Kentucky bluegrass are alive and will grow with more consistent warmer temperatures.
If there are parts of the lawn with bare soil the question is what to do? If there is Kentucky bluegrass surrounding thin or bare areas, the spots can fill in over-time especially with a sound fertility program. If there is no Kentucky bluegrass or the areas are large, renovation will be needed. Spring however is not the ideal time to do seeding. If seeding is done there may be poor germination and weak establishment of the desired grass. At the same time weeds quickly germinate and are often a major problem. So this may be a challenging year! Much depends on the weather and if there is a long mild spring for the cool-season grass to fill in and develop a deep root system before the heat and stress of summer.
Hopefully this helps explain some of what we are seeing in lawns at this time.