Mowing is the most common cultural practice used on lawns around the world. In fact the ability to tolerate mowing is one of the criteria that separate turfgrasses from the rest of the grass species. There are many misconceptions about mowing that can lead to a less than perfect lawn and many homeowners are making lawn care way to difficult by using the wrong mowing practices.
Mowing is always a stress on the grass plants. Just because they can tolerate the act of mowing does not mean they like it. Try and reduce the stress on the plant by mowing early in the morning or even better in the evening. Mowing during the heat of the day can cause the plant to go into shock. Mow when the grass is dry. Your mower will work better and there is less likelihood that disease will be spread from plant to plant.
Never mow off more than one third of the leaf tissue in one mowing. If you are mowing your grass at 2 inches don’t let it grow over 3 inches. A drastic decrease in height can shock the plant. This doesn’t mean you can let it grow to 4 inches and mow off 1 inch in the morning and another in the afternoon. The plant will show the signs of this abuse.
Make sure your mower blades are sharp. Dull mower blades will tear the grass instead of cutting it. This often leaves a tan or brown cast to the lawn after mowing. Torn grass blades are more likely to get infected with a fungus than nicely cut grass. Check the turf often after mowing to make sure your equipment is in good condition.
Leave your clippings on the lawn. Clippings are full of nutrients and can actually reduce your need for fertilizers. Grass clippings readily breakdown and will only cause an issue if the quantity is excessive. Mulching mowers are great at making the clippings small enough but even standard discharge mowers will not cause a problem if you are following the one third rule.
Mowing often lays the grass over slightly (this is how the patterns develop) and it is important to mow in a different direction often so the grass does not lie over excessively. Changing the pattern can also reduce wear and compaction by changing the areas that are traveled.
Recommended Mowing Heights
Kentucky Bluegrass 2-3 inches
Tall Fescue 2-3 inches
Perennial Ryegrass 2-3 inches
Fine Fescues 2-3 inches
St. Augustine grass 1.5-3 inches
Bermuda grass 0.5-1.5 inches
Zoysia grass 1-2 inches
Centipede grass 1-2 inches
Buffalo grass 3-4 inches
Mowing Heights Effect Lawns
It is always best to maintain these grasses at the top end of these height ranges. Leaving the grasses longer has many benefits. Longer grass shades the soil keeping it cooler which will reduce evaporation of water from the soil. This shade also reduces the opportunity for weed seeds to germinate. If grass is shortly mowed it will have much more weed pressure.
Think of the grass blades as solar panels for the plant and the roots are the energy storage cells. Leaving grass blades long increases the size of the solar panels and results in greater energy storage and root growth. Root growth is often directly proportional to top growth. The longer the grass blades the deeper the roots, allowing grass to find water and nutrients at greater depths.
It is often thought that if you mow the grass shorter it will allow for a longer duration between mowing. This is untrue. Shortly mown grass wants to rapidly grow back what it has lost. The grass will pull reserves from the roots to increase shoot growth. This decreases rooting and increases the chance the lawn will show signs of drought or heat stress.
The only time mowing short is advocated is late in the fall in those climates that see snow or temperatures below freezing for over 30 days. Mowing short this last mowing will reduce matting of the grass in the spring and decrease the chance of cool season fungal diseases called snow molds.
Grass can neglected to the point that it grows too long. Over a certain height grass will not support its own weight and will begin to fall over. This can cause the underlying grass to be smothered and die. This can also lead to excessive moisture being trapped in the turf canopy increasing breeding of fungal diseases.