Sun Deficiency June 7, 2019 By John Daniels, agronomist, Central Region

Numerous rainy and cloudy days have hindered turf quality, particularly for warm-season grasses which require more sunlight.

The theme for many golf courses in 2019 can be summed up in one word: soggy. In fact, the continental United States just had the wettest 12-month stretch in the 124 years since measurements started. This unprecedented amount of precipitation has resulted in numerous challenges for golf courses.

Bunker washouts, cart restrictions, disease outbreaks, flooding, unmown grass, plugged lies and other maladies have been common complaints on golf courses from Texas all the way up to Minnesota. Most of the negative impacts that extreme rainfall has on turfgrass health and playing conditions are obvious. Improving drainage to expedite the removal of excess water is an intuitive remedy. However, there are more than a few examples of areas that drain rapidly – such as sand-based putting greens – where turf conditions are still struggling, leaving some to wonder what is going on.

We must not forget that turfgrass does best when it receives ample sunlight. Each day it rains is one day where plants likely did not receive the necessary quantity of sunlight for sufficient photosynthesis. Even those rain-free, cloudy days can severely restrict turfgrass growth and development. One or two consecutive days is no big deal, but a week or more of cloudy conditions and turf will certainly show signs of decline. This is especially true for warm-season turf species, like bermudagrass, that have high sunlight requirements.

Instead of simply counting the number of rainy days or the amount of precipitation that accumulated in a given month, consider evaluating the number of sunny days as well. A lack of sunlight may explain why some areas of your course have struggled as of late. Perhaps addressing shade issues through selective tree pruning or removal could provide relief and ensure that your turf is getting the most sun possible.


Central Region Agronomists:

Bob Vavrek, regional director –

John Daniels, agronomist –

Zach Nicoludis, agronomist –

Information on the USGA’s Course Consulting Service 

Contact the Green Section Staff

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