Heat Stress: How hot times are impacting creeping bentgrass

Creeping bentgrass putting greens are subjected to annual summertime heat stress. Rising temperatures surround the plant with rapidly rising air temperatures. Rising soil temperatures bathe the plants and low mowing heights make conditions extreme.

Although creeping bentgrass has excellent heat tolerance compared to most cool-season turfgrasses, the added factors of wear and moisture can enhance susceptibility to heat stress.

High temperatures cause detrimental effects on creeping bentgrass by impacting various physiological processes such as photosynthesis, respiration, water use efficiency and nutrient uptake. Reduced photosynthetic activity in creeping bentgrass can cause a decline in carbohydrate production and storage. This ultimately leads to weakened turfgrass with reduced energy reserves, making them more susceptible to environmental stresses and diseases.

Furthermore, heat stress disrupts the balance between water uptake and transpiration in creeping bentgrass. Under hot conditions, creeping bentgrass may experience increased water loss through transpiration, leading to dehydration and wilting of the turfgrass. Water stress can further exacerbate any negative symptoms.

Nutrient uptake is a critical process that can be affected by high-temperature stress. As soil temperatures rise above 70 degrees F then approach or exceed the mid 80s, those high temperatures can impair the root system’s ability to absorb essential nutrients from the soil, leading to nutrient deficiencies in the turfgrass plants. This nutrient imbalance can hinder overall growth and development.

Prolonged exposure to heat can also cause browning, thinning and patchiness in creeping bentgrass, diminishing its visual appeal. Often alone or exacperated by moisture deficits, the leaves become thin and spindly, almost like fine fescue, leading to an appearance of decreased turf density.

To mitigate the impact of high-temperature stress on creeping bentgrass, golf course superintendents can implement various cultural and management strategies. These may include proper irrigation scheduling to maintain soil moisture levels, appropriate fertilization to support turfgrass health and aeration to improve soil oxygenation and root development. Regularly scheduled plant growth regulator applications can help maintain a quality turf during summer stress by slightly limiting moisture stress through reducing transpiration. The impact of reducing transpiration is measurable but not severe enough to add to temperature stress.

Transpiration is the most effective process for cooling plant temperatures. Evapotranspiration dissipates heat from the plant. In situations where shade exists, like shaded putting greens or greens in low-lying areas, air movement across the turf is needed. Consider tree removal as an effective means for increasing air movement, which also provides more light to the turf. Properly installed fans are effective means for cooling turf when the removal of trees or other obstructions is not possible.

When possible, I recommend choosing heat-tolerant creeping bentgrass cultivars. Identifying the best heat tolerant cultivars is not as easy as “give me a list.” I’ve found that getting as much input from experts in your region is a good place to start. Check with university researchers in the area, your seed company and your fellow golf course superintendents to see what they recommend. If a number of golf courses in your area have had good success with a specific cultivar or two, that is a strong starting point.

High-temperature stress can have significant implications for creeping bentgrass health and performance, making it crucial that superintendents understanding how plants regulate temperature and act accordingly.