Dan Undersander's grass variety trials show as much as a 4 ton/acre annual yield difference between the top and bottom entries of the same species.

That difference underscores a point the University of Wisconsin Extension forage agronomist makes to growers: Variety selection is more important in grasses than in alfalfa, corn and soybeans because the differences are greater.

“I always tell farmers there's as much difference between grass varieties as there is between an Angus and a Holstein cow,” says Undersander.

He urges growers to choose varieties meticulously, whether the grass will be grown as a stand-alone hay or silage crop, mixed with alfalfa or seeded as part of a pasture mix. Usually, picking top performers means buying newer, more expensive varieties instead of older ones, but you'll want to review nearby test data to find out how they have fared under conditions similar to yours. Most newer grass varieties were developed in other countries, and some can't withstand northern winters.

“We've seen this time and again where some of these New Zealand grass varieties come in and they're just not winterhardy enough for us,” says Undersander. “So one of the things that's really important is local testing, particularly for winterhardiness.”

He heads the most extensive grass variety testing program in the region, with trials at four locations throughout Wisconsin. Results are posted at www.uwex.edu/ces/forage.

“We don't have every variety on our Web site, but we have a slug of them, and we encourage people to look at that,” he says.

In addition to winterhardiness, Undersander says to look for later-maturing varieties with high yield potential and good season-long yield distribution.

Late maturity is important because, if the grass will be seeded with alfalfa, you'll want both to head about the same time. Some newer varieties do, but older ones tend to mature earlier. Older orchardgrass varieties, for example, head as much as three weeks earlier than some newer ones.

“That's a big deal,” says Undersander. “It's not four or five days; I'm saying two or three weeks.”

Maturity is an issue if the grass will be grown with clover in a pasture, too. Again, you want a variety that matches the legume's maturity.

“I would generally recommend a medium to late type everywhere, except if somebody just wants a single hay crop off a field.”

Yield distribution can be more important than total yield, but the two traits tend to go together: High-yielding varieties usually produce well over multiple cuttings. Avoid varieties that produce 40% or more of their yield in the first cutting and a lot less in later harvests.

On the Wisconsin Web site, yield distribution is listed as beta, which is the slope of a line connecting the yield, or percentage of total yield, of each cutting. A flat line indicates good yield distribution, and a very negative slope means a high percentage of the yield is in first cutting.

“We're recommending a slope or beta of between -1 and +1, but if it's a -6 or -8, maybe you ought to look elsewhere.”

Finally, if you're choosing varieties of orchardgrass, tall fescue or meadow fescue, the species Undersander recommends for the Upper Midwest (see accompanying story), look for rust resistance. Rust is a big problem in much of the region, he says. It causes the orange dust that rubs off on shoes and pants in late summer. It reduces growth and cattle don't like rust-infected grass so will avoid eating it.