and Providence and 100-150% denser than Penncross. They are comparable to the dense stands of Poa annua var. reptans, found in many old push-up greens, and appear similar to the finest velvet bentgrasses in density and texture. People often cite their high-density characteristics as a mechanism to prevent annual meadow- grass ingress. Does this happen? Well, in reality no, annual meadow-grass can still invade these surfaces, if injured or thinning occurs particularly during the dormant winter months. Annual meadow- grass invasion is determined very much by the levels of winter play. A study at Ohio State University showed that newer varieties with high shoot density (A and G series) have more roots in the spring than earlier varieties. The higher root densities can aid in pest and stress tolerance. This may become more of a concern if hot, dry summers become more frequent.
Mowing, rolling and ball marks - Close mowing helps to retain grass density and these grasses thrive on a tight cutting regime. The optimum mowing heights are between 4mm and 3mm, however some of the newer varieties have been mowed as low as 2.5mm during tournament play. It is common for some courses to roll greens once or twice weekly to minimise the need to reduce the mowing height. There has been concern that the newer cultivars are not as aggressive as
Penncross and this is one reason why ball marks seem to be more evident on greens planted with the newer varieties. However, studies have shown that these new varieties actually heal just as quickly if not sooner than Penncross. It is felt that this perceived problem was a result of comparing very young turf, having little mat for cushioning, to older Penncross that had developed a cushioning mat. It seems that the ball marks become less noticeable as the green ages, no matter which variety is chosen.
Topdressing - Topdressing with sand that is comparable to the green mix is the most effective means of preventing thatch accumulations. Weekly or bi-weekly applications are the norm in the US. The high shoot density of the newer varieties can lead to quick thatch production if managed incorrectly. I had the pleasure of visiting Bayville Golf Club, Virginia in 1997, one of the first courses in the States to seed to Penn A4 in 1995. Cutler Robinson, the Superintendent there, explained the maintenance regime to me then. Topdressings were applied to match
growth rates and Cutler was aiming to apply 30-35 dressings over the year (weekly during the growing season). Surface preparation consisted of double cutting on 169 occasions and double rolling on 32 occasions. Greens were single cut on 93 occasions and rolled once on 157 occasions.
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