"On occasions, bentgrass and Poa annua greens develop soft, puffy qualities that tend to ridge or buckle into a slightly higher position than established by the mower. The loose, dense, poorly rooted growth makes a poor putting surface. This slight unevenness occasionally enables the mower to grab chunks of the soft, puffy turf and its scalps or gouges the surface. This produces a poor green."
Although I do not want to get too technical into the plant morphological reasons for "puffiness", understanding the potential causes may help explain the success/failure of certain management practices. So lets take a moment and look at a dense putting green turf.
As a general rule 2.7 to 3.1 live leaves occur per tiller regardless of density (Cattani and Clark, 1991). Thus, the density of the turf is maintained through tillering. If we look at the primary tiller it produces leaves and can also produce additional tillers from its base. Tillering is an organized system that is well structured. Tillers appear in a specific sequence and are influenced by the plant population density. Turfgrass tillers can be classified as lower order and higher order tillers. The lower order tillers are considered primary tillers that emerge close to the base of the primary tiller, while the higher order tillers are produced from subsequent axils of later emerging leaves. Higher order tillers generally appear slightly higher in the canopy. In dense turf, higher tiller orders tend to be smaller (maybe more succulent), more competitive for light, and predominate over the lower order tillers (Cattani and Struik, 2001). Now, should these higher tiller orders elongate through internodal elongation the leaves associated with these tillers are raised higher into the canopy causing the turf to become "puffy". Obviously, this is not an easy thing to visualize, but hey what do you expect from a professor.
If we go back up to the Engle description of "puffy" we can see that "dense" and "unevenness" may be a result of the internodal elongation of the higher order tillers favored due to the high density plant community. The higher order tillers produced tend to be succulent (soft), easily pulled upon, and the leaves from these tillers are elevated above the canopy (unevenness)
A shallow root system is characteristic of a puffy green. Thus an unbalanced relationship between tillering and root growth is important in puffiness. At this time of the year with high soil temperatures, reduction in root growth or loss of root system is common for creeping bentgrass and annual bluegrass causing an imbalance in tillering capabilities and root growth. For those maintaining annual bluegrass greens this imbalance of high shoot density and low root density is pretty evident. Interestingly, I think we are seeing the same relationship with the new high shoot density bentgrass cultivars and the ultradwarfs (I know some golf course superintendents who are managing the ultradwarfs are freaking out over the shallower root system then what would normally be expected with a bermudagrass).
Management Practices for Puffiness:
Nitrogen Fertility: It makes sense that practices that stimulate tillering over root growth will contribute to puffiness. Excessive nitrogen applications during active shoot growth contribute to puffiness. For example fertilizing heavily in spring during a flush of growth will favor tillering over root growth. Thus, puffiness can occur in spring if nitrogen applications are excessive and applied during the flush of shoot growth. In addition, during late summer high soil temperatures along with soil moisture increases mineralization of organic matter and the release of "natural" nitrogen that could promote puffiness.
Coring: This practice can help reduce puffiness of the green by opening up the turf and promoting greater light penetration to the plants around the core hole. Thus, the lower order tillers, closer to the surface will spread laterally and not elongate vertically like the higher order tillers. Coring with small diameter tines like quadra tines, or star tines, should help reduce puffiness. In addition the coring depth could be shallow since you are trying to promote tillering close to the base of the plant not necessarily trying to relieve compaction.
Verticutting: Light verticutting, and I emphasize light, is also a means of removing some leaf tissue and providing more light down into the canopy. This may promote lower order tillering (the good tillering).
Topdressing: By raising the surface you help reduce the scalping associated with puffiness. Light frequent topdressing is especially critical to minimize puffiness with Poa annua and high shoot density creeping bentgrass cultivars, as well as the ultradwarfs.
Mowing: If puffiness is occurring scalping from mowing can occur. To help reduce the likelihood of scalping switch to solid rollers, and minimize dropping mower units when engaged at the start of mowing pass. The new flex head type-mowing units present the potential for less scalping on puffy greens. However, I do not have any first hand knowledge or information to support this idea.
Beard, J.B. 1973. Turfgrass: science and culture. Prentice-Hall, Inc. Englewood Cliffs, N.J.
Cattani, D.J., and K.W. Clark. 1991. Influence of wear stress on turfgrass growth components and visual density ratings. Can. J. Plant Sci. 71:305-308.
Cattani, D.J. and P.C. Struik, 2001. Tillering, internode development, and dry matter partitioning in creeping bentgrass. Crop Science:41:111-118.
Authors: Karl Danneberger