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An unfortunately underused and usually unappreciated grass

What is this underused and unappreciated grass? It is tropical carpetgrass (Axonopus compressus), the species that C.V. Piper, the first chairman of the USGA Green Section, wrote about as "the best of all grasses in the South for fairways." Piper added that:

It makes a dense, uniform turf even on pure sands and the leaves are stiff enough so that the ball is always well off the ground. The only other grass to compete with it is Bermuda; but under conditions where both will grow, carpetgrass makes far superior turf.

Tropical carpetgrass is the climax species as a managed turf in humid tropical climates. But it is barely mentioned in turfgrass textbooks, probably because the authors have focused primarily on the grasses in common use in the United States.

This is unfortunate, because tropical carpetgrass has a number of advantages as a turfgrass compared to species such as bermudagrass (Cynodon) or seashore paspalum (Paspalum vaginatum) that are sometimes planted in tropical environments. For example, it is possible to maintain tropical carpetgrass with no supplemental fertilizer, no irrigation, and no pesticides. In fact, that would be standard maintenance for tropical carpetgrass in many places – mowing, and not much else.

With these advantages compared to other grasses, it is encouraging to see two recent papers that have investigated some characteristics and performance of tropical carpetgrass.

Springer et al. compared bermudagrass, zoysiagrass, and tropical carpetgrass (they use the name savannahgrass for Axonopus compressus) at the University of the West Indies. They measured how much these grasses grew, and what quality they produced, when subjected to drought stress, waterlogging, and soil compaction. This was done in soil and in soil profiles with a surface sand layer to simulate the effects of sand topdressing.

Tropical carpetgrass through the green on the East Course at Wack Wack Golf and Country Club in Manila, Philippines

The full paper, Comparative Evaluation of Common Savannahgrass on a Range of Soils Subjected to Different Stresses I: Productivity and Quality, shows that tropical carpetgrass (savannahgrass) generally performed better in the growing environment of Trinidad than did the bermudagrass or the zoysiagrass. Averaged across all the stress treatments, tropical carpetgrass had the greatest clipping yield and the highest chlorophyll index. Zoysiagrass had the highest visual quality averaged across all stress treatments, with carpetgrass just behind, and then bermudagrass having the lowest visual quality.

Springer et al. concluded that tropical carpetgrass "showed a higher level of tolerance to applied stresses and warrants greater attention as a potential turfgrass under tropical conditions." 

Tropical carpetgrass provides a full turf cover in heavy tree and structural shade at Bali, Indonesia

In Nigeria, Oyedeji et al. investigated tropical carpetgrass and other local grasses. Their paper, Performance of Some Local Nigerian Turfgrasses in Sole and Mixed Stands, shows data that again make a strong case for tropical carpetgrass as a turf in that climate. Compared to other grasses, tropical carpetgrass performed well, especially in the recovery after 2 weeks of daily trampling with soccer boots.

Unirrigated carpetgrass during the dry season at Hua Hin, Thailand

In a tropical climate, it is hard to find a grass that outperforms tropical carpetgrass. One of its advantages as a turfgrass is its adaptability to a range of mowing heights. Tropical carpetgrass can be maintained with almost no inputs, except for mowing, and in addition to that, it can be mown at heights from 3 mm to more than 100 mm. 

A patch of tropical carpetgrass on a manilagrass green maintained at 4 mm in Chumpon, Thailand
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