Lateral spread and divot recovery of creeping bentgrass cultivars

A host of improved cultivars of creeping bentgrass have been released onto the market that possess improved agronomic characteristics such as vertical shoot growth, higher shoot densities, and narrower leaf blades. While many believe these morphological characteristics create an improved playing surface there are questions about the ability of these improved varieties to spread laterally compared to older varieties such as Penncross. While it is generally agreed that creeping bentgrass possesses relatively high recuperative potential, minimal research has focused on differences among cultivars of creeping bentgrass. The objectives of this research were to determine differences in lateral spread and divot recovery of 24 cultivars of creeping bentgrass in mowed and non-mowed settings. The results of this research would help turf managers select cultivars of creeping bentgrass to match specific site requirements.
I started the study June 1 by transplanting 100 plugs of creeping bentgrass (24 different cultivars) into a fallow area. Prior to transplant, the area was treated with Basamid in order to limit competition from weeds. The plugs were simply allowed to grow, unabated, throughout the season.

The second component of the study involved creating simulated divots by removing a core of turf and soil from the same 24 cultivars with a cup cutter and backfilling the area with soil. No seed was added. The “divots” were simply allowed to grow and heal back in. The maintenance of the area was designed to simulate golf course fairway conditions.

I used a new piece of technology to evaluate the progress of the study called Digital Image Analysis. The software is able to distinguish between different colors (green turf and bare soil in this case) and calculates the percentage of green turf in the picture. With some simple calibrations and calculations, I am able to determine the rate of spread of each of the cultivars.

What we found
Stolon Growth … Non mowed. Differences among cultivars were observed for lateral spread. Penncross had the fastest establishment rate and Bengal had the slowest. The cultivars SR 1150, Crenshaw, Imperial, Kingpin, L-93, MacKenzie, Crystal Bluelinks, Pennlinks II, Penn G-6, Putter, Memorial, Penn A-4, and Tyee all had establishment rates statistically similar to Penncross. The others had growth rates slower than Penncross.

Divot Recovery – Mowed. Differences among cultivars were observed for divot recovery rate. Imperial had the fastest recovery rate and Alpha the slowest (Table 1). The cultivars Penn G-6, Alister, SR 1150, Crystal Bluelinks, Southshore, Penncross, L-93, and Century all had divot recovery rates statistically similar to Imperial.

While the differences appear small, consider that divots can take anywhere between 6 and 10 weeks to heal depending on the time of year and the management conditions.

One of the big factors influencing lateral spread of grasses with stolons is the length of the internodes. As I stated earlier, the improved cultivars of creeping bentgrass posses higher shoot densities. This is possible because these cultivars have shorter internodes, thus a higher number of shoots per area.

I measured the internode length of all 24 cultivars and the general trend is that grasses with longer internodes (lower shoot densities) spread faster than grasses with shorter internodes (higher shoot densities). The take home message, there is a trade-off between lateral spread and shoot density. This trade-off between recuperative potential and shoot density needs to be considered when selecting cultivars for specific use areas. Higher shoot density cultivars may be better suited for areas where lower populations of annual bluegrass are desired. Alternately, lower shoot density cultivars may be better suited for areas where damage from divoting is severe and recovery is important.

Marcus Jones
Graduate Research Assistant
Iowa State University