Canal bank weeds

We have a drainage canal with long, sloping banks that grow up in willows, maple, alder and several other woody shrubs. We are looking for an approved aquatic herbicide that will kill unwanted trees and shrubs but won't kill the grasses. What products are approved for this use?
— Alabama

Because you want to preserve the grasses, you'll need a selective product. Renovate, a SePRO product that uses triclopyr as the active ingredient, has labeling that fits the situation you describe. It is registered for emergent plants, including woody plants that are growing on the banks, as long as the canal doesn't carry irrigation water.

There are also several conventional brush-control products on the market that might be suitable for this use. They may offer less flexibility than Renovate because they may be more tightly restricted regarding their use near bodies of water. However, depending on the site (i.e., how close the brush is to the water and how tightly you can control your spray), they may be acceptable.

I checked with Earl Tracy, a vegetation management specialist with PBI/Gordon (which makes BrushMaster herbicide). He confirmed that this product and similar phenoxy-based herbicides are, if so labeled, appropriate for canal and ditch banks. The keys to complying with such brush-control product-use instructions on canal banks are keeping the material away from the water and avoiding use on irrigation canal banks (as opposed to drainage canals). Be sure to carefully read and follow the label before use.

More on “low-mow” bluegrasses

In April, we responded to a reader looking for “low-mow” bluegrasses. We subsequently heard from a reader in Alaska whose par-3 course consists entirely of Nugget Kentucky bluegrass. And that includes the greens.

The reader explained that he originally used Nugget on fairways and tried several types of bentgrass for the greens, without much success. Then he began mowing some of the Nugget shorter and shorter; “just experimenting,” he said. It worked, and he has been doing this for 15 years now, mowing the bluegrass as low as ⅜ inch (but a little longer going into the winter). The bluegrass suffers very little winter damage, but does encounter a bit of snow mold “if it goes into the winter too short.”

How does it play? “It's a very good putting surface,” he says, with stimp readings as high as 10.

I also followed up with a couple of turf breeders. According to John Rector, a turf consultant for Turf Seed Inc. (Tangent, Ore.), many athletic field managers clip their Kentucky bluegrass at low for a quicker ball bounce.

Dr. Doug Brede, with Jacklin Seed (Post Falls, Idaho), explains that while some courses are using Kentucky bluegrass for agronomic reasons (such as resistance to gray leaf spot), it also exhibits good playability for less-advanced golfers. At ½ inch, it tees the ball up so golfers can make shots without taking large divots.

Close-cut Kentucky bluegrass is not an entirely new thing, according to Rector, who says that the relatively old variety Midnight has long been known for its tolerance to close mowing. Brede agrees, adding that Merion Kentucky bluegrass was noted for its tolerance of relatively low mowing heights in the 1950s. However, it wasn't until the 1970s, according to Brede, that Kentucky bluegrasses truly tolerant of practical fairway heights became available: Touchdown (a Pickseed variety), which tolerates ⅞ inch or so, was the first.

In the mid-1980s, several other varieties were introduced, such as Limousine, and breeders have continued to work on this trait. Now there are numerous varieties available, according to Brede, that can tolerate “a practical half-inch mowing height.”

According to Rector, maintenance is more critical for closely mowed Kentucky bluegrass. In particular, a smooth surface is important because scalping can cause unacceptable damage if the turf has an uneven surface. Thus, topdressing and other cultural practices that promote surface uniformity are vital. Brede concurs, explaining that below ½ inch, it is difficult to maintain a smooth-enough surface to avoid scalping Kentucky bluegrass. Courses that desire such lower heights typically use bentgrass instead.

Eric Liskey has a bachelor's degree in ornamental horticulture and a master's degree in botany. He has been licensed for pesticide advising and applications in California and Missouri, and has more than 10 years combined professional experience in landscape installation and maintenance, nursery retailing, pest management and botany.

If you have a question about landscape or turf management, write to “Researching Maintenance,” Grounds Maintenance, P.O. Box 12901, Overland Park, KS 66282-2901, or send you question by e-mail to

Questions are selected on the basis of current general interest. We cannot guarantee a response.

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