Michigan State University Arboretum highlights ash alternatives

From Nursery Management

Bert Cregg, Robert Schutzki, and Roy Prentice | October 5, 2012

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The summer of 2012 marked the 10-year anniversary of the discovery of emerald ash borer (EAB) in southeast Michigan. The ash borer is a phloem-feeding beetle from Asia that girdles and kills host ash (Fraxinus sp.) trees. Since its introduction near Detroit, EAB has continued to spread rapidly across the Upper Midwest and eastern United States, often with the unknowing aid of campers and others moving firewood. As of Aug. 1, EAB has been confirmed in 16 U.S. states from Minnesota to Connecticut and two Canadian provinces. Although researchers have made progress on a variety of fronts in the battle against the beetle, the future of most native Fraxinus species in North America remains in doubt.
Green and white ash were popular choices in landscapes and as street trees because of their good growth rates, fall color and adaptability to a wide range of site conditions. The rapid demise of ash trees in the wake of EAB has been truly remarkable and has resulted in a significant loss of urban tree canopy in many communities. A recent study projected that EAB will result in the loss of 17 million ash trees in urban and community forests by 2019. As with Dutch elm disease before it, the EAB saga demonstrates the vulnerability of native trees to exotic pests for which they have not evolved resistance. As the likelihood of additional exotic pest introduction increases with global trade, the need to diversify our landscapes and reduce the risk of catastrophic tree loss is greater than ever.

Ash alternatives
To evaluate ash alternatives and promote increased species diversity in areas affected by EAB, we established an arboretum at MSU Tollgate Education Center in Novi, Mich., near the epicenter of the original EAB outbreak. In the spring of 2003, a small army of volunteers descended upon a hillside at the Tollgate Center armed with shovels, rakes and water hoses. The volunteers planted nearly 200 1½-inch bare-root shade trees representing 37 different ash alternative selections (five trees per selection). The trees were donated by J. Frank Schmidt and Sons Nursery and Carlton Plants. Additional support was provided by the Michigan Nursery and Landscape Association and MSU Project GREEEN. After planting, the trees were mulched with 3 inches of wood chips and irrigated during the first summer to aid in establishment. Initial survival of the planting was excellent although deer have taken their toll despite the addition of plastic guards to the tree trunks. Listed below are some of the selections that have proven to be solid performers in the ash alternative arboretum during the past decade.

State street maple provides a winning combination of growth rate and dark green foliage.

State Street maple Acer miyabei ‘Morton’
Acer miyabei is native to Japan and this selection was made by the Morton arboretum. In the Tollgate planting, trees have a good growth rate (25’ after 10 years) with a dense crown and dark green foliage. We have seen little evidence of pest problems. USDA Hardiness Zone 4.

Hardy rubber tree Eucommia ulmoides
Hardy rubber tree is native to China, where it is relatively rare in the wild. It is hardy to Zone 5 and considered to be relatively pest free. At Tollgate, trees have shown good form and characteristic glossy green leaves. Growth rate is intermediate (20 feet) among trees in the arboretum.

American Sentry linden Tilia americana ‘McKSentry’
Redmond linden Tilia americana euchlora ‘Redmond’
Greenspire linden Tilia cordata ‘Greenspire’
We included three linden selections at Tollgate and all three have been outstanding. Average heights after 10 years were 20 feet for Redmond linden, 22 feet for Greenspire and 23 feet for American Sentry. All three have great pyramidal form and excellent, dark-green leaf color. American Sentry hardy to Zone 3; Redmond to Zone 3; and Greenspire to Zone 4.

American Hophornbeam Ostrya virginiana
Hophornbeam is among the slower-growing trees in the planting (14 feet after 10 years) but it has been a steady performer with good leaf color and form. The hop-like flowers add to its visual appeal. Hardy to Zone 4.

Greenspire linden

Northern pin oak Quercus ellipsodalis
Northern pin oak is another tree in the “slow-but-steady” category. (11 feet after 10 years). The alkaline soils at Tollgate (pH = 7.5) turned out to be a perfect site to demonstrate the greater pH tolerance of Quercus ellipsodalis compared to the standard pin oak (Q. palustris). Northern pin oak maintained dark green leaves while pin oaks on the site became extremely chlorotic. Hardy to Zone 5.

Shingle oak Quercus imbricaria
Shingle oak is primarily a southern species and Michigan is on the northern fringe of its native range. Nevertheless, shingle oak was an intermediate grower in the arboretum, averaging 19 feet at 10 years. The trees had dark green glossy leaves. Hardy to Zone 5.

Sawtooth oak Quercus accutissima
Like shingle oak, sawtooth oak doesn’t have deep lobes on its leaves like most oaks. Sawtooth oaks grew slowly (15 feet at 10 years) in the arboretum, but their sharply serrated leaves still provide plenty of interest. Hardy to Zone 5.

Accolade elm Ulmus japonica × wilsoniana ‘Morton’
One of the ironies of the EAB story is that we are now recommending elms to replace ashes, many of which were planted to replace elms lost to Dutch elm disease. Accolade elm is part of new group of hybrid elms that have been selected for tolerance to Dutch elm disease. Accolade elms were among the fastest growing trees at Tollgate, averaging 27 feet at age 10. Hardy to Zone 4.

Triumph elm Ulmus ‘Morton Glossy’
As with Accolade elm, Triumph elm is hybrid elm selected at the Morton arboretum for Dutch elm disease tolerance. Triumph is also a fast grower (27 feet at age 10). In fact, Triumph elms grew so fast in the arboretum that they literally blew the plastic dear guards off their trunks. Hardy to Zone 5.

Yellow buckeye Aesculus flava
Although we don’t usually say good things about buckeyes at Michigan State, yellow buckeye has proven to be a good performer in the Tollgate planting. Growth rate has been intermediate (19 feet at ten years) and the trees have maintained good form and remained pest-free. Hardy to Zone 4.

Top Left: That’s an oak?  Shingle oak demonstrates not all oak leaves are lobed. Top Right: Northern pine oak (R) was able to maintain deep green leaf color, while pin oak (L) became extremely chlorotic. Bottom left: Accolade elm was one of the fastest growing trees in the demonstration planting. At age 10, the trees are developing attractive vase-shaped crowns. Bottom Right: Hophornbeam fruit provides added visual interest to this small to medium sized tree.

Bert Cregg is associate professor, Plant & Soil Sciences, Michigan State University, cregg@msu.edu; Robert Schutzki is associate professor, Plant & Soil Sciences, Michigan State University, schutzki@msu.edu; and Roy Prentice is farm manager at Tollgate Education Center, prentic1@msu.edu.

Distinguishing Ash From Other Common Trees

It's not always easy to figure out if that tree you're worried about is an ash tree.

"Distinguishing Ash from Other Common Trees" is an educational bulletin created at Michigan State University Extension. This bulletin describes how to identify ash, as well as common trees that may look like ash, but aren't. This is available http://www.emeraldashborer.info/files/E2892Ash1.pdf">online.

This publication is also available for purchase. To order, call 517-353-6740, or go to http://bit.ly/czVqhu and ?Search by Publication? for E2892. Copies are 10¢ each (plus shipping and handling, with a minimum order of 100 copies). Great for an educational presentation, as a handout during meetings, or as a reference guide for municipalities, arborists or tree care companies.

Using Infested Ash to Make Bats

More on the use of ash bats in Wilmette......

Rising from the Ashes

from Plenty Magazine

In every crisis, there are those who panic, and those who see the opportunities. Ash trees are dying by the millions in the Midwestern United States due to an invasive pest called the emerald ash borer, a shiny green beetle a half-inch long that preys on ash trees. The upshot is that ash wood—long relegated to utilitarian uses in tool handles, baseball bats, and firewood—is finally getting its due: Under the apt title “Rising from Ashes,” the Chicago Furniture Designers Association is organizing a series of exhibitions that, starting this August at the Morton Arboretum in Chicago, will feature furniture made of ash wood from trees killed by the emerald ash borer.

“This is one heck of an education tool,” says Bruce Horigan, a member of the association who owns Horigan Urban Forest Products, a hardwood sawmill in Skokie, IL. Horigan says the exhibition is a chance not just to clue people in about the ash borer and invasive species in general, but also to show them there “are better uses for [ash wood] than firewood or mulch.”

Ash is a hard yet springy wood (it was once used in snowshoe frames), ranging in color from creamy white to chocolate brown – perfect for durable, attractive furnishings. “This is visual lumber,” Horigan says. “It’s not the two-by-four behind the wall; it’s the paneling in front of the wall.” But most people don’t think of it that way – or didn’t, until ash suddenly became very available.

Though the emerald ash borer probably arrived in North America from Asia in the 1990s, it was first detected in Michigan in 2002; it has since spread across the Midwest and as far as West Virginia. It’s of particular concern in Illinois’ urban areas, where 20 percent of the trees are ash wood. The pest lays its eggs just under the bark of the ash tree, and when the larvae hatch, they feed on that sub-bark layer, eventually killing the tree. But it can be difficult to tell when a tree is infested: Dieback is gradual, and the tiny larvae lie dormant in winter and remain in the wood even after the tree dies. The danger is that people don’t realize that the wood they’re transporting is infested, says Edith Makra, Community Trees Advocate at the Morton Arboretum and a member of the Illinois Emerald Ash Borer Wood Utilization Team, a consortium of around 80 foresters, arborists, and anyone interested in using ash wood and fighting the ash borer. Since then, the Illinois Department of Agriculture has embarked upon an awareness campaign and enforces strict quarantines on firewood to keep the ash borer contained – though Makra says it’s still hard to detect.

So a traveling furniture exhibition featuring previously infested ash wood sounded like an ecological disaster waiting to happen – that is, until Bruce Horigan explained the process under which he’s licensed to treat ash wood. The outermost layers of the tree—where the ash borer lives and eats—are ground up into tiny pieces too small to support the larvae. The rest of the wood – which technically is free from infestation because the ash borer’s larvae can’t penetrate the core of the tree – is heated in a kiln for 48 hours, just to be sure. Ash wood furniture, as long as it’s made from the heart of the tree, is perfectly safe. The only battle is getting people to want it.

“The idea of wood utilization has been around with urban foresters for years,” says Makra. “We’ve talked about how frustrating it is that we take down all these valuable trees in urban areas and nobody [uses] that timber.” Trees in urban areas are seen as less desirable, Makra explains, because they may have imperfections (like a nail from an old garage sale sign), or because a city may lack the infrastructure or extra budget to mill individual trees. But that could change, especially if exhibitions like “Rising from Ashes” have their intended effect. Studies show that if urban timber (trees that succumb to disease or injury) were fully utilized, it could provide up to 30 percent of the United States’ timber needs. That would mean fewer trees logged from forests. How that timber is used matters, too: According to Horigan, burning firewood and spreading mulch release a lot of carbon directly into the atmosphere, whereas “higher” uses – like furniture – that leave the tree intact keep that carbon sequestered in the wood. With all the ash trees dying, there will be a surplus of ash wood no matter what, so using some of it for furniture might be preferable to having a bunch of extra mulch lying around.

John Kriegshauser and Dolly Spragins, co-chairs of the “Rising from Ashes” exhibition, say they expect up to 30,000 people to view the work of their 29 designers. After two weeks at the Morton Arboretum, the exhibition will visit furniture companies and conservation centers around Illinois through next spring. The featured pieces can be sold, but Spragins says they have to stay in the show – so designers who make a sale must craft duplicates for their customers. The exhibition comes with the support of urban wood utilization groups like the Illinois Emerald Ash Borer Wood Utilization Team, which received a $100,000 Forest Service grant last year. Similar grants have gone to groups in Michigan that seek to combine urban wood utilization with education about the ash borer.

No one’s saying the emerald ash borer is a good thing. In addition to quarantines and monitoring, scientists are looking for solutions –some ideas that have been batted around include introducing parasitic wasps that eat ash borer larvae, cross-breeding American ash trees and their more resistant Chinese counterparts, or injecting trees with pesticides. But as long as the trees are falling, why not keep their beauty – and their carbon – around in the form of artistic design? It’s a simple case, in Horigan’s words, of making lemonade out of lemons.