Verdure: An ode to Tom Watschke

The turfgrass scientist’s early work helped shape our understanding of turf physiology and tolerance to high temperature stress. Plus: Watch a national morning show’s 1990 interview with Dr. Watschke.


The idea for this column came from Cale Bigelow, Ph.D., of Purdue University, and it’s a tribute to Thomas (Tom) Watschke, Ph.D., the longtime professor of turfgrass science at Penn State who died in November of last year.

Watschke’s youth was spent in Charles City, Iowa, and his original career track led to him becoming a dentist. Perhaps his future was redirected while working for his older brother at a local golf course. He earned a Bachelor of Science in horticulture from Iowa State and a master’s and doctorate in agronomy from Virginia Tech. His graduate studies were guided by Richard Schmidt, Ph.D., a Penn State alum. Upon graduation in 1970, Watschke joined the turfgrass science faculty at Penn State. He retired in 2005.

Watch: Tom Watschke made an appearance on “Good Morning America” in 1990 to share mowing tips for homeowners. Check out the rare clip:

Watschke’s early research published in 1970 is worth revisiting, because it helped pave the way for future studies that increased our understanding of turfgrass physiology.

In controlled greenhouse experiments, five Kentucky bluegrass cultivars were grown in solution culture (~hydroponics). The Kentucky bluegrass cultivars were three commercially available ones of the time — Pennstar (improved selection from Merion), Kenblue (a common type), Nugget (a selection from the cold climate of Alaska) — and two experimentals selected from the warmer climate near Virginia’s coast. Ten weeks after seeding, turf was clipped in each pot to 2.5 inches (6.3 centimeters), and roots trimmed to 1 inch (2.5 centimeters), so that all turf started the experiment on equal status.

The Kentucky bluegrass cultivars were subjected to two nitrate (NO3-N) fertility levels of a low versus high amount at 15 or 150 parts per million (15 or 150 milligrams per kilogram), and three day/night temperature regimes of 64/50 F (18/10 C), 81/64 F (27/18 C) or 95/68 (35/20 C). All treatment combinations of Kentucky bluegrass and NO3-N and temperature were replicated and randomized, and all received 18 hours of light and six hours of dark every day for the duration of the 10-week experiment. Items measured were shoot growth, root growth, NO3-N uptake, carbohydrate content (using a hot water extraction method, the latest technology at the time) and leaf NO3-N content.

What were the results? Let’s start with the interaction of temperature and N. Not surprising for cool-season Kentucky bluegrass, all cultivars performed poorly at 95/68 F with low or high NO3-N. Best shoot growth across all cultivars was observed with high N at 64/50 F or 81/64 F, and best root growth across all cultivars was measured at 81/64 F and least at 95/68 F with low or high NO3-N.

Let’s look at how those cultivars responded to temperature. Kentucky bluegrasses originating from warm climates were more tolerant of high temperature because they had higher carbohydrate levels, lower NO3-N uptake and lower foliar NO3-N content than Kentucky bluegrasses from cold climates. Therefore, Kentucky bluegrasses from warm ecological regions are better adapted to high temperature stress because of low NO3-N absorption, which limits stimulation of NO3-N metabolism, thus conserving carbohydrates.

But wait, there’s more.

In a “preconditioning” follow-up experiment, all Kentucky bluegrass and NO3-N treatment combinations were subjected to 95/68 F for 30 days, to compare measurements with the first part of the experiment. Watschke found that all Kentucky bluegrasses preconditioned at cooler temperatures produced more shoot growth but had lower N absorption and higher carbohydrates compared to all Kentucky bluegrasses maintained at the continuously higher temperature. So, turf with high carbohydrates best supports growth at high temperature. Watschke stated, “Apparently grasses with reasonably high carbohydrate contents, whether induced by fertility, management, or genetic composition, enhance Kentucky bluegrass tolerance to high temperature stress.”

Editor’s note: Research on 14 cool- and warm-season grasses — including Kentucky bluegrass — offers greater guidance on selecting surfaces to withstand extended periods of heat. Read the findings in Turfgrass responses to prolonged heat stress.

Watschke’s research from the 1970s guided future investigations into summer stress physiology and performance of cool-season turfgrasses by many faculty and graduate students. Also of note: While at Penn State, he established the first formal turfgrass science baccalaureate degree program, with “Turfgrass Science” printed on the diploma. Prior to that, students majored in agronomy or horticulture. He was a fellow in the American Society of Agronomy and the Crop Science Society of America. In 1990, he received GCSAA’s Col. John Morley Distinguished Service Award.

Thank you, Dr. Tom Watschke, for your contributions to turfgrass science.

Source: Watschke, T.L., R.E. Schmidt and R.E. Blaser. 1970. Responses of some Kentucky bluegrasses to high temperature and nitrogen fertility. Crop Science 10:372-376.

Mike Fidanza is a professor of plant and soil science in the Division of Science at the Penn State University Berks Campus in Reading, Pa. He is a 19-year member of GCSAA.