Turf grass Spring Greenup
While it is the end of May and many warm-season grass species have greened-up, some
bermudagrass and zoysia grass lawns still have a significant amount of old, brown, leaf material
in them. This is likely the result of several compounding factors.
The impact of last fall’s long, hot, dry weather are likely affecting green-up this season, especially in non-irrigated lawns. A second factor influencing green-up could be all the rainfall this winter. Water is a good buffer of heat. Meaning that it takes more energy (i.e. from the sun) to warm a wet soil than a dry soil. To
date, the average 4-inch soil temperature for the entire month of May in Griffin, GA – central for
the state – is 71.2 F.
That is 5.6 F lower than for the same time last year. Similarly, the
average maximum air temperature this May has been 8 F cooler than May 2019. Lastly, of the
pictures, descriptions, and observations I have made, the lawns with considerable brown have a
higher mowing height than is recommended for bermudagrass and zoysia grass.
The mowing range should be 1.0 to 2.0 inches. The extra leaf canopy and thatch can act as an insulator, like the pink stuff in your attic and walls, preventing the sun’s energy from warming the soil quickly.
For these lawns I have suggested the grass be mowed as low as possible and remove all the leaf
biomass.
The objective is to open the turf canopy, permitting sunlight to reach the soil surface.
Taking it a step further, consider core aerification. Opening holes into the soil profile permits
warm air into the root zone, warming the soil from the inside-out. By warming the soil,
rhizomes will initiate new shoots, eventually reaching the soil surface and thickening the lawn.
