A premium BLEND
A blend of turf varieties, it's been said, is like carrying a full bag of golf clubs. Each club is well-suited to a particular situation: woods work better for distance; the wedge and putter excel for close-up shots. A full bag of clubs prepares you for whatever circumstance you're likely to encounter.
Combining two or more varieties of grass in a lawn or sports turf likewise increases your probability of success. Chances are, one of the components will have the resistance to shade, drought, cold or the prevalent diseases and insects necessary to create a uniformly healthy turf. Plus, no turf sward — no matter how small — is perfectly uniform edge to edge. All have pockets of damp and dry, or shade and sun, and varying soil properties that necessitate a turf of diversity.
Blending is more common with certain grasses than others. For example, it is rare to blend varieties of bermudagrasses. Bermudagrass, zoysiagrass, St. Augustinegrass and buffalograss are almost always established as a single variety. That's because if you blend them, they tend to segregate into unsightly patches and swirls.
Blending is more customary with the cool-season turfgrasses, however. Most ryegrass and fescue seed is sold as a blend of varieties. While this is desirable to do, it is not imperative. From an agronomic standpoint, blending may be superfluous with these grasses, because ryegrass, bentgrass and fescue varieties tend to be broadly based (genetically speaking), with a good spectrum of adaptation within each variety. Blending often is done more out of tradition than anything else.
With Kentucky bluegrass, blending is more important. Bluegrass is unique among the turfgrasses in that it reproduces by a process called apomixis. In apomixis, the seed develops from the mother's genes but not the father's. As a result, nearly every seed in the bag is a genetic clone of the mother plant. That's why lawns of Kentucky bluegrass look so uniform. It's also why bluegrass varieties are blended — to expand the amount of adaptive variation in the turf.
WHAT BLENDS DO AND DON'T ACCOMPLISH
Disease and insect problems are the main motivation to blend bluegrasses. No bluegrass variety is resistant to all pests. Combining them allows one variety's strengths to make up for another's deficits.
Handled properly, blended varieties should stack up as neatly as in Figure 1. In this example, Variety A is resistant to stripe smut disease, but it is susceptible to dollar spot, brown patch and leaf spot. Varieties B and C have different strengths and weaknesses. A blend of the three (bottom row in diagram), should possess resistance to all of these four problematic diseases.
That's the theory. Now let's look at the practicality and economics.
High-quality varieties — those that have solid performance and a broad-spectrum of pest resistance — are generally more expensive. On the other hand, susceptible varieties — ones with glaring flaws — are generally cheaper.
Years ago, the prevailing thought was that if you blended an expensive variety with a cheaper type, the superior variety would completely mask the weaknesses of the poorer one. Here's an example: Let's say premium Variety X sells for $4 per pound, while inferior Variety Y sells for $2. If you're trying to minimize your seeding expense, Variety Y would give you the lower price but at a sacrifice of quality. So, let's say you mix X and Y in a 50-50 combination. The price of that would, of course, be $3 per pound. But what would happen to the quality and pest resistance?
Research has discovered that a blend like this would produce a stand that displays intermediate characteristics, depending on how much of each variety makes up the blend. In their paper, The principles of blending Kentucky bluegrass cultivars for disease resistance (International Turfgrass Society Proceedings, 1980), Drs. Joe Vargas and Al Turgeon concluded that: “Where two cultivars differ substantially in their respective susceptibilities to melting out or Fusarium blight [disease] are combined in a blend, disease incidence usually represents a compromise between that occurring in the monostands of the component cultivars. Thus, the disease may be less than that of the susceptible cultivar but more severe than that occurring in the resistant cultivar.” The study's performance curve was similar to the idealized chart in Figure 2. Good varieties do not conceal poor varieties in blends; they only add a beneficial element to the blend.
A popular misconception about blends is that good varieties over time will push out weak ones. Unfortunately, this is sometimes heard from seed salesmen who have diluted a good variety with a cheaper, low-end type. In truth, a low-performance variety can express itself in your turf for years, possibly forever. In the Vargas and Turgeon study, they followed the disease susceptibility of blends for several years and concluded, “It was surprising that the blends remained intermediate in melting-out incidence for the 3 to 4 years following establishment. It would be more reasonable to expect the melting-out-resistant cultivar to dominate each blend because of its superior competitive ability during periods of disease activity. This was not evident.”
Therefore, when choosing varieties for your blend, pick carefully. Weak varieties may be there to haunt you for years.
MENU OR Á LA CARTE?
You can purchase seed of bluegrass blends in two ways:
As a “preform” — a pre-measured, pre-formulated combination of varieties concocted by the seed supplier (see Tables 1 and 2).
As a “custom mix” — a blend of varieties specified by the customer.
Most turf blends are sold as preforms. A preform has the advantage of being a tested-and-true combination of varieties. Successful preforms are sold in the millions of pounds, giving you some assurance that these varieties have bonafide agronomic advantages and that other customers have used them with success.
Preforms do vary in composition from year to year. This is good and bad. On the positive side, the seed vendor is always seeking better varieties as they come available. Each year, a preform blend should actually get better in quality. On the negative side, the blend you planted last year might not be the one you're seeding today.
Larger turf growers — especially sod farmers and landscape companies — sometimes specify their own custom blends. One Midwestern sod producer proudly offers a sod blend with seven custom-blended varieties — far more than the two to four varieties most use. Custom blending can require more lead time than using preforms. It may also cost slightly more if the supplier tacks on blending charges. Blending charges are usually absorbed in the price of preforms.
Blending turfgrass varieties is a good agronomic strategy. However, as with any single turfgrass variety, it pays to get quality components, preform blends help ensure that you get a tried-and-true combination. Doing so will help you get a uniform turf even if your site isn't.
Dr. Doug Brede, formerly a professor of turfgrass management at Oklahoma State University, has been developing Kentucky bluegrasses at Jacklin Seed/Simplot since 1986. He's the creator of several bluegrass varieties including Absolute, Arcadia, Award, NuGlade, Liberator, Odyssey and Chicago II. Brede is the author of a new book dealing with useful ways for lowering your turf maintenance, entitled “Turfgrass Maintenance Reduction Handbook.” It can be found at the publisher's Web site (www.sleepingbearpress.com) or at your local turf trade show.
THE DIFFERENCE BETWEEN BRANDS, BLENDS AND VARIETIES.
When a new variety is released, it goes through a naming and registration process administered by the federal government. No variety now or 100 years from now (theoretically) can ever have the same name. That's to prevent the public from being misled. Purchasing the seed of a certified variety guarantees you that someone in the government has inspected the seed for trueness-to-type and purity.
But what does a seed company do with the warehouses of seed that do not meet government standards? That's where brands come in. Brands are a valid safety valve for the occasional unexpected overproduction. Blends and brands allow the seed company to legitimately switch off ingredients to suit this year's harvest.
Here's how a seed brand works: First, I pick a sexy name and register it with the U.S. Trademark office. Next, I must use the brand name in advertising or sales to make it legally valid. Finally, I must use the word “brand” along side the name wherever I use it. And that's the key for how you can spot brands and tell them from varieties. For example, Sunrise brand is a popular seeded zoysiagrass line. Is Sunrise a variety? No. It is whatever I wish to put into the brand today.
Of course, companies do not purposely try to defile their good brand names. Most endeavor to put good ingredients into successful brands and blends. Once a brand name is tarnished, it's next to impossible to resurrect.
BLUEGRASS GROUPING METHODS MAY GUIDE BLENDING
The basic theory of blending is to combine varieties that make up for each other's weaknesses. The guiding philosophy of blending in the past was to combine varieties of similar color and blade width to prevent clashes. Blending a yellow-green variety with a dark bluish-green one would produce a speckled turf, or so it was asserted.
Two research groups have taken the idea of blending one step further, attempting to classify bluegrasses by their growth habits and even the DNA of their genes. Drs. Jim Murphy and Reed Funk at Rutgers University were the first to advance a grouping system for blending. Over the years, Funk noticed that varieties on his research farm that stayed green in the winter coincidentally had susceptibility to certain diseases. He also noted that dark-green, low-growing varieties tended to exhibit a different set of susceptibilities.
“I went out to the plots one day in mid-January and put wooden stakes facing one direction in all the ones I called ‘Bellevue types’ and stakes facing the other direction in the ‘BVMG types,’” Funk recalls. He then asked Murphy, Rutgers' extension specialist, to look over the plots. “Jim…could see a great difference between the two types but no difference within the types.”
Funk and Murphy initially grouped the bluegrasses into six categories, along with a nebulous “Other Types” category. Today their number of groups has risen to nine and counting.
Funk's philosophy is: “If you want a Bellevue type in there, just pick the best Bellevue type that performs best for you. There's no point in adding more than one Bellevue type to a blend.”
Dr. Geunhwa Jung of the University of Wisconsin Plant Pathology department has proposed an even more radical approach to blending. Jung is a laboratory scientist with the ability to tell varieties apart by the sequence of their genes. He proposes that turf managers should combine varieties with different DNA patterns. To choose groups for blending, Jung uses DNA probes, examining the genetic blueprint at several locations along the chromosomes. He then recommends blending only varieties with dissimilar banding patterns.
Neither method has been empirically tested in the field to confirm its validity. Nonetheless, they offer food for thought for blending bluegrass varieties, over and above the yellow vs. blue-green argument.
Photo — Digital; In August folder
A batch of ‘Field of Dreams’ Kentucky bluegrass blend is created by the blending operators at National Seed of Downers Grove, Ill. The basic seed blending machine has remained virtually unchanged for decades. Seed is conveyed into the top and kitchen-style mixer blades uniformly combine the seed.
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