Warm Weather and Spring Mowing Woe’s – Turfgrass Science at Purdue University

Warm Weather and Spring Mowing Woe’s

For those that are managing cool-season lawns like Kentucky bluegrass, the ryegrasses or fescues the unseasonably early warm spring weather has resulted in quite a bit of shoot tissue (leaf clippings) being produced. For many that think they want their lawns to look like a closely cropped and highly manicured golf course, this may have resulted in the need to mow much more frequently than in previous years. Sometimes twice or more per week. I have had some people comment that they feel like they are “baling hay” each time they mow this year. These excess clippings are unsightly and can cause problems in terms of shading the turf. If you have felt like you are tired of baling hay and are interested in reducing your mowing frequency to a more manageable once every 7 days, carefully consider your intended mowing height. For most cool-season lawns we generally recommend that you mow between 2.5-3.5 inches. Even small alterations in your intended mowing height can change your need to mow from roughly every 6 days to nearly every 9 days (Table 1). Obviously a slightly higher mowing height, 3.0 vs. 3.5 inches, will require less frequent mowing. Additionally, this higher mowing height will result in a potentially deeper root system, more leaf surface area for photosynthesis and the ability for clippings to more easily filter back into the turf canopy when returned to the lawn or “mulch mowed”. As we say about mowing lawns, “Mow high and let them lie”….

Table 1. Relationship between intended mowing height and mowing frequency.

Mowing height

Turf height at cutting (a)

Grass removed

Estimated mowing frequency (b)

——————— inches ——————–

— days —

1.0

1.50

0.50

2.5

1.5

2.25

0.75

3.8

2.0

3.00

1.00

5.0

2.5

3.75

1.25

6.3

3.0

4.50

1.50

7.5

3.5

5.25

1.75

8.8

4.0

6.00

2.00

10.0

a Turf height at cutting assumes the “1/3 Rule” is being practiced and never removing more than 1/3 of the leaf blade in any one single mowing.
b Estimated growth based on an average daily growth rate of 0.2 inches

Excess clippings can shade and damage lawn turf


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