Turf Update —
Growing Turf in Low Light A Presentation by Dr. Aaron Patton
by Meta L. Levin
Turf needs light to grow, but conditions
often mean there is too little or poor quality light available. Sometimes, property owners have unrealistic expectations of where it is and is not possible to grow grass on their lawns. If you are nodding in understanding, then you would have been right with Aaron Patton during his Turf Education Day presentation, “Growing Turf in Low Light, Shaded Environments.” Patton, interim department head and professor in Purdue University’s Department of Horticulture and Landscape Architecture, took attendees through a basic primer on photosynthesis, the process by which plants trap the sun’s energy to build carbohydrates to use as stored energy. It is a lightdependent action and that light comes from the sun. At this point, we will need a glossary, albeit a short one: 1. Shade environment: an area with reduced light, moderated temperatures, low air movement, high humidity, and longer periods of leaf wetness 2. Photosynthetically Active Radiation (PAR): The term for wavelengths of the visible light spectrum, between 400 and 700, which plants use for photosynthesis.
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3. Photosynthetic Photon Flux Density (PPFD): The units used to measure PAR 4. Daily Light Integral (DLI): A 24-hour measurement of PAR So, how much daylight do grasses need to grow? “This is a question we are still trying to answer,” says Patton. It is dependent on several factors, not just sunlight, including temperature, grass species, mowing height, and plant nutrition. In fact, the shorter you mow the grass, the more light it will need, says Patton. There are apps, such as Sun Seeker, that help track the amount of sun on different spots. In the case of Sun Seeker allows you to track the sunrise and sunset times, as well as check the sun position and solar path over the lawn. The cost is $9.99, if you are interested. An app like this will help you not only show the path over the lawn, but give you an idea of where the most shade is coming from, where it’s going to be in a couple of months, and where it was a few months ago. “Most grasses prefer full sun, except on the scorching
The Landscape Contractor June 2020
