Choosing Turfgrass

Summary

Turfgrass choices are the species, cultivar, type of planting material, and quality, for a specific site. In conjunction with choosing the turfgrass, the landscape and turfgrass manager is concerned with getting the turf to the site in healthy condition. The lecture will contain much more specifics, so this write-up is intended to provide a foundation.

Why?

The consequences of turfgrass selection are both long- and short-term, and somewhat unpredictable. Long-term consequences of turfgrass selection include longevity, maintenance cost, and suitability of a turf to a site or use. Short-term consequences of turf selection are the purchase price, including any delivery or contract installation costs, and associated costs such as consultant's fees, travel to visit the sod farm, and inspection costs.

Hardest to estimate in turfgrass selection are risk factors, that is, the variability of, performance and quality. A grass that does well on one site may do poorly at another, due to factors that were not known or not sufficiently understood previously. Although plantings at both sites cost the same initially, the failed planting may cost two or more times as much as the successful planting.

A turfgrass species such as bahiagrass, Paspalum notatum, may be poorly adapted to a site because it requires more illumination (i.e., "photosynthetically active radiation") than the site provides, due to tree shade. Such a planting in South Florida fails typically within two years, as the bahiagrass thins and becomes infested with weeds.

Hybrid bermudagrass, Cynodon sp., is sometimes planted as an accent for high-end properties such as homes for the wealthy. Such an application serves to provide a visual distinction from neighboring properties, but often the maintenance costs is out of proportion to the benefit, for that use.

Knowing how to choose a turfgrass enables the landscape and turfgrass manager to make appropriate decisions for the client or employer.

Species and cultivars

There are hundreds of turfgrass cultivars available. Few are suited to a particular use. In Florida a vegetatively propagated clone, 'Floratam' St. Augustinegrass, dominates the vast majority of planted landscapes, and is usually the largest component of all landscapes. This is impressive, especially considering that the developer Dr. G. C. Horn, "nearly threw it away (personal communication, 1985).

Considering the preeminence of Floratam St. Augustinegrass, landscape and turfgrass managers would be highly concerned in having a reliable, affordable source for Floratam. But Floratam has problems, and often the client asks for alternatives, some of which may be highly touted. The landscape or turfgrass manager who can provide information, or who can find and assess information from others, will be in a better position to serve the client in the choice of turf.

Choice of a species and cultivar is ideally a design decision made by a professional landscape architect also responsible for woody plant selection and placement, walkways, walls, terraces, and supervision of irrigation contractors, and environmental site plans. In reality, landscape architects often do not have local experience to make sound turfgrass selection decisions, and rely on others. Furthermore, the landscape and turfgrass manager often chooses the turfgrass as a part of a renovation project that is handled in-house.

Type of plant material

Turfgrasses are planted with three to five different kinds of plant materials, depending on how you want to classify them:

     seed - Sexual products of grasses, consisting of mature fruits (caryopses) and associated bracts. Because grass caryopses are often tightly held in their modified bracts (glumes, lemmas, etc.) the "seed" of grasses is almost always a higher level unit, floret, spikelet, or bur. In some cases, e.g., 'Argentine' bahiagrass the caryopsis is produced through a form of asexual reproduction, apoximis, so that it is vegetative, and all Argentine bahiagrass is the same plant. Typically, seed is sold by weight.

     sod - Flat chunks, slaps, or rolls of turfgrass canopy and attached roots, in which the vertical projection exceeds the horizontal. Sod may be produced from vegetative reproduction or seed. Sod pieces may be installed to form a continuous canopy or may placed distantly, "spot-sodded." Sod may be harvested, transported, and installed intact, or may be washed free of soil. Typically, sod is sold by unit area, or by transport unit, e.g., pallet.

     sprig - Stem cutting consisting of one or more nodes which can root. Sprigs may be harvested by shredding sod, or by mowing tall canopies, or more often uplifted by chiseling slender slices ("dug"). Sprigs tend to dry out quickly and are highly perishable. Sprigs are typically sold by unit volume.

     plug - A small, well-held-together chunk of grass containing canopy and roots. May be a small piece of sod about as deep as it is wide, or may be a vertical cylinder from the field, or may be produced in a container tray. Plugs are typically sold by the unit, or by the transport unit, e.g., tray or pallet.

     stolonizing - This is a planting method, not a type of plant material, but it typically involves sprigs which are long enough to be laid in narrow trenches.

Quality

Purity, viability, and packaging determine the quality of turfgrass planting material, along with other factors such as soil type and pest infestation. Purity refers to the consistency of planting stock. Is it genetically true to type? If it represents a clonal cultivar, pure would mean that there is no genetic variation. For all types of plant material, the main concern is to avoid contaminants of the same species. Seed labels describe the occurrence of weed species, which can be a serious problem, but contamination from the same species is usually more serious.

Grass seed can remain viable for 20 years or more, depending on storage conditions. Optimum storage for seed is cool and dry. Seed tests evaluate the ability of seed to germinate under controlled conditions, but postharvest dormancy can lead to incorrect interpretations.

Sprigs remain viable for 1-14 days, generally, but because this is living plant material, it dries out quickly.

Sod remains viable for 2-7 days, generally. The biggest mortality factor for sod is or oxidative decomposition, which results in high temperatures.

Packaging methods are constantly changing turfgrasses. The pallet, adopted for Florida turfgrass sod in 1957-58, had tremendous impact.