Is it a blend or a mixture? A blend contains different cultivars of the same species, whereas a mixture contains seeds of several different species, such as Kentucky bluegrass and perennial grass.
Photos by John C. Fech, UNL, unless otherwise noted.
When things go wrong with a client's turf the typical response is to make an educated guess as to the cause and to recommend a quick inexpensive solution. Usually, the focus is on what is readily apparent i.e. the 6 inches in front of your face. While this approach often works well in the short term, it usually results in facing the same problem again in the near future. Instead of a hurried reaction, utilizing a holistic, it's almost always more effective to go with the big picture process, meaning to consider all of the factors that may contribute to a malady.
Originally devised to combat the cotton boll weevil, the integrated pest control (IPM) method uses all available methods to keep weeds, insects, nematodes and diseases at tolerable levels. One of the most important factors (and it's often overlooked) is selecting the appropriate turf species and cultivars for the site.
On a definition or technical level, grounds managers and lawn care providers plant and maintain many turf species, usually comprised of improved cultivars of each. In many situations, the species are combined to gain the benefit of each and decrease the chances for a particular pest to cause the demise of the stand. For example, if Bipolaris leaf spot becomes an issue in the turf, and only one cultivar of a particular species is being grown, there is a great deal of pressure on those grass plants to hold up to the potential infection or virulence of the disease. There is even more pressure if the cultivar has a history of suffering from Bipolaris leaf spot.
To broaden the genetic tolerance to various diseases and gain other benefits such as cold tolerance, shade resistance and recuperative potential, species are often combined to create a mixture. With this in mind, you will find low maintenance mixtures available as well. These mixtures may contain a combination of species like sheep fescue, buffalograss, annual ryegrass (for rapid establishment) and blue grama. They normally require little mowing or irrigation (once established) and are great for industrial sites or large low maintenance utility turf sites. As well, different cultivars of a single species are included in a seed product to further add genetic diversity. A blend contains different cultivars of the same species. A mixture contains seeds of several different species, such as Kentucky bluegrass and perennial grass.
Some seed blenders then get creative and may include up to five varieties of one species, let's say tall fescue for an athletic field for durability. If they add a Kentucky bluegrass for sod strength and damage recovery, then top it off with perennial ryegrass for rapid establishment, they have created a seed mixture inasmuch as it contains three different species - tall fescue, Kentucky bluegrass and perennial ryegrass.
Right plant, right place
Choosing turf species and cultivars is really just another iteration of the right plant, right place model. In the landscape, we focus heavily on RPRP, selecting trees, shrubs, perennials and groundcovers with site specific features in mind. Plant height/width, leaf and flower color, season of bloom, sun/shade preference, disease resistance, landscape litter potential, architecture and growth habit are several of the factors considered during the selection process. It's really no different for turf, as it is very important to get the right species and cultivar in the right place in the overall landscape. For both turf and ornamentals, the place to start is with site assessment and evaluation.
Evaluation and site assessment
A close examination of a property will yield results in terms of placing the most appropriate turf plants in place and providing them with the greatest chance for success. A large number of factors should be considered in order to be thorough and successful. While there are several possible ways to assess a property, a walk and talk with the property owner usually yields the most dividends. In this way, they will see your level of concern for the property and the desire to perform at a high level. Additionally, they may be able to provide helpful insights into the history of the site that may otherwise go unconsidered.
As the property is evaluated, notes should be made about the effects of the ornamentals on the turf as well as the condition of the turf itself. For example, the location and type of shade should be noted. It's helpful to categorize shade as heavy, filtered, dappled or light. As well, the level of shade changes throughout the season in relation to the degree of sunlight on the horizon. The trees and shrubs that produce the shade (as well as buildings and houses) have a direct effect on air flow and potential impact on disease pressure and should be noted as well. If available, information about previous disease and insect outbreaks is valuable. Disease- and insect-resistant cultivars are a primary selection criterion.
Lawns in the so-called transition zone often contain both warm- and cool-season grasses. They require different management strategies, which challenges lawn care pros.
Photo by Brad Jakubowksi, Doane College.
Notations about the level of traffic received are useful in terms of species and cultivar selection. Certain locations in both commercial and residential properties are often more heavily used by pedestrians; traffic-tolerant species are best utilized in these spaces. A home lawn that is beat down by several kids and dogs may be a real challenge when it comes to picking out turf species and cultivars; in some cases, creating a path or play area may be better than actual turf.
Location is always a key factor in terms of deicing salt spray. For example, in hell strips along streets, buffalograss may be a good choice because of its deep rooted nature and capacity to draw water from deep in the soil. However, it is not particularly salt-tolerant and if commonly used, could present problems. Along these lines, narrow strips and out of the way or oddly shaped spots in the landscape are often difficult to irrigate. As such, this becomes a selection factor; bermudagrass, buffalograss and turf-type tall fescues are among the species that perform best. Irrigation is often a key factor related to the overall maintenance level. After categorizing a property into high, medium and low maintenance with the input from the property owner, work with suppliers to choose products with the specific level in mind.
Other selection factors
Other selection factors are critical as well. Color is very important to some property owners and not so much to others. Yes, grass is green, but it comes in many shades from light to dark green, sometimes with a tinge of blue. As with all factors, there can be tradeoffs with color. For example, many of your midnight blues or darker green Kentucky blue grass varieties have a tendency to be susceptible to powdery mildew. Texture is another visually appealing component, with most customers preferring fine over coarse. Improved cultivars of bermudagrass and tall fescue incorporate finer texture.
Selection Criteria for Each Species
Especially in fall when time is short to obtain a stand or during football season when the team is out of town for a couple of weeks, establishment rate can make or break the success of a particular seeding operation. A fast-growing cultivar will perform better in terms of resisting weed invasion, controlling erosion and recovering from pest damage. Yet, fast growth can often lead to short life or greater thatch production potential.
In terms of the extremes of the temperature and other weather conditions throughout the country, especially in the transition zone, the heat and cold tolerance of a particular species or cultivar can be a cause of turf failure and thus a reason for selection or de-selection. In the North, tall fescue has a reputation for poor cold temperature tolerance, especially in the establishment year. In many parts of the country, rough bluegrass exhibits poor high temperature tolerance. Within the species of bermudagrass, certain cultivars are adapted to southern and northern climes.
The growth habit can be a consideration during mixing or blending in that some cultivars are characteristically upright, while others are low growing and stay close to the soil surface. This is a consideration in that the more upright the growth habit, the more mowing operations are required. Some species are inherently more upright than others; plant breeders continue to work on developing prostrate growing cultivars as the marketplace demands it.
Seed mixtures provide better disease resistance along with improved cold and drought tolerance.
Choose turf for the site
The purpose of the product - the requirements for the eventual end use - influence the species and cultivars chosen as well. For example, on a campus grounds, an entirely new area can differ in terms of appearance than a spot-seeding. With the latter, a high importance is placed on blending in with the existing grasses as opposed to a large section of turf, where the value is more likely to be viewed in light of how well it fits in terms of overall maintenance level.
The location or application of the end use of the product will also influence the species and cultivars chosen. A home lawn, industrial park, shopping mall and sports field differ with regards to maintenance level, expectations of the property owner and budget for installation and care.
Some turf cultivars (as shown here) are more disease prone than others. Visit the NTEP website to compare susceptibility of the cultivars for your region.
Check out NTEP
The National Turfgrass Evaluation Program (NTEP) is a great source of unbiased data - and it's free! Sure, it takes a little in the way of being able to understand statistics, but university extension faculty and most suppliers are well-versed in reading and interpreting tables and differentiating between least significant differences between cultivars and are more than willing to work with lawn care operators and grounds maintenance companies to make sound decisions for selection of well-adapted turf seed products. Information on NTEP and its services can be found at http://www.ntep.org.
John Fech is an extension educator specializing in turf and ornamentals at the University of Nebraska-Lincoln. You can reach him at firstname.lastname@example.org. Brad Jakubowski is an instructor at Doane College.