Hort Peeve: New Sod Torture

Tony Koski, Extension Turf Specialist

The lawn before mowing; that blue flag is 12 inches tall!

This turf peeve is about the mowing of newly planted sod. For some reason, the principles of proper mowing height and frequency are often totally neglected with new sod - sometimes for weeks on end. I’ve been watching the sod that was planted during the renovation of the old Fort Collins post office landscape over the past 6 weeks. The old lawn was replaced with new bluegrass sod – and then taped off as if it were a crime scene. The new sod went unmown for about 3-plus weeks – but was liberally irrigated during that time. As you might expect, it grew tall….VERY tall. So tall, in fact, that it began flopping over (aka “lodging”).

The lawn an hour after mowing torture

The lush, floppy, dense grass was recently mowed to a height of about 3 inches. What was left behind is not pretty – a mess of wet, matted, rutted brown and yellow grass. Mowing in this fashion will kill roots – roots that have been formed in just the previous few weeks. The stressed turf must not only grow a bunch of new leaves and shoots to replace those that were hacked off during mowing – but also will have to produce new roots to replace the ones that died as a result of the severe mowing.

This first mowing left few green leaves...and what happens
when the 1/3 rule is violated so egregiously!

This turf torture occurs all too frequently when new sod is planted. For some misguided reason(s), mowing of the newly planted sod often doesn’t happen for 2-4 weeks following planting. Sometimes the sod supplier tells a client it is better to leave the sod unmown for weeks on end because it will form better roots than if mowed “too soon” (not true). More often it is out of laziness, neglect or fear that new sod isn’t mowed. Because new sod should be irrigated daily, the water must be turned off for a day prior to mowing to give the sod a chance to dry out a little. This temporary drying out of the new sod takes planning and coordination with the person doing the mowing – and it creates the (unjustified) fear that the short-term drying will harm the turf.

The truth is, grass should always be mowed when it needs it – to avoid removing any more than 1/3 of the turf height at a single mowing (we call this the “1/3 rule”) – even if it is new sod.  Luckily, newly planted bluegrass sod is amazingly forgiving of neglect and mismanagement – so this lawn will likely survive and (eventually) look good. I will keep you updated.

Here is the lawn 1 week after its first mowing. Still recovering
from misinformed (stupid?) management. This is someone's
idea of proper turf management?