We cut grass slightly higher than some clients are used to, and thought we would take the opportunity during September’s first ApeMail to explain the science behind it.
This week our Mowing Operations Manager Jason von Reyn (pictured above) answers five questions on cutting height and thatch buildup to alleviate some of the mystery behind lush, thick turf. He’s Landscape Industry Certified, been with us for five years, and cut his way from Jr. Mow Crew Technician, to his first season as Mowing Operations Manager in 2017.
How is cutting height determined?
Cutting height depends primarily on the current length, the type of grass, and if the lawn is irrigated and/or fertilized. Normally we mow between 3-3.75″ depending on the lawn, but gradually step down in 1/4″ increments each week during Fall time, with 2.75″ at the lowest level.
Why do we slowly reduce cutting height during Fall?
Mainly to maintain root health while reducing the amount of thatch buildup as leaves and other materials collect. Root health is one of the most important factors in lush grass. The taller the grass, the deeper the roots which allows for increased moisture retention. We like to step it down slowly when Fall begins so that leaf litter and thatch do not build up too thickly. Build up of 3/4″ or more can promote disease and decay even during Winter months when grass is dormant.
What happens if grass is cut too short?
If the grass is cut too short (more than 1/3 of the total height removed during a weeks growth) it will put stress on the roots and they will die back resulting in yellow grass.
How can you tell if there is too much thatch?
All the thatch settles to the surface of the soil which provides nutrients to be recycled, slows down water loss and improves the turfs tolerance from compaction. Too much thatch is usually around ¾ inch thick which will create too much insulation and prevent water, fertilizer, pest controls and sunlight from reaching the soil and lower grass blades.
What can a homeowner or Landscape Professional do if thatch buildup goes beyond a healthy level?
We usually address this on our own and client lawns in Spring during the first cut or cleanup as a preventative for the season, as well as to “fluff” the turf. Our crews prefer to use mower-mounted tine rakes due to the speed and efficiency of simultaneously mowing and dethatching. Normal metal leaf rakes work great as well but are easy to overdo and remove too much, causing an adverse effect. There are also specialty vertical mowers (sometimes known as “Verticutters”) that help dethatch and straighten individual blades of glass, but these are typically unnecessary and impractical for most residential applications.