Farm Horizons, November 2011

More elm trees, please

By Starrla Cray, Staff Writer

After Dutch elm disease wiped out 192,211 elm trees in the seven-county metropolitan area of the Twin Cities in 1977, many people became wary of the tall, fast-growing plant.

However, that doesn’t mean the elm tree doesn’t have a place in Minnesota landscapes.

“The key is diversity,” said Jim Wilson, owner of Wilson’s North West Nursery near New Germany. “There are very few trees that don’t have some problem.”

After the widespread loss of elms in the 1970s and 1980s, many cities planted an abundance of ash trees.

“The ash trees were used to replace the elms, because of Dutch elm disease, and now, because of emerald ash borer, elm trees are being used to replace the ash trees,” Wilson said. “It’s come full circle.” When Wilson opened his nursery in 1983, he didn’t grow any elm trees.

Now, they have at least 500.

“We’re probably growing more elms than we ever have,” he said, adding that city foresters are the nursery’s primary elm tree customers.

“The general public is coming on board, but it’s a slow process,” Wilson said.

Boom and bust

During the first half of the 20th century, elm trees were immensely popular, promoted for their tolerance to urban environments, long life, and resistance to pests.

Unfortunately, Dutch elm disease, which is caused by a wilt fungus that grows on the sapwood of elms, was found in the Netherlands in 1921.

At first, Minnesota was considered too far north for the elm bark beetle that transports the disease to thrive, but the first case was reported in 1961, according to the University of Minnesota Extension.

The disease was most likely brought to Minnesota from a state farther south, either on beetles or on wood contaminated with the fungus.

Dutch elm disease slowly gained a foothold, and by 1972, Minneapolis had 222 diseased elms. The number peaked in 1977, with 31,475 diseased elms. It then decreased due to disease-control programs, and by 1987, 2,280 trees in Minneapolis were infected.

The city spent $8 million in 1978 for elm disease control, including tree and stump removal, trimming, insect and disease control, inspection, and replanting.

Before the Dutch elm disease, Minneapolis had more than 200,000 elm trees, according to the U of M Extension.

Lesson learned

According to Wilson, most cities have learned not to plant any one kind of tree excessively.

Elm trees are also being developed for disease-resistance.

Wilson’s North West Nursery sells three hybrid elm varieties, including Accolade, Triumph, and Discovery.

Two American varieties – Valley Forge and Princeton – are also sold.

Many people are fond of the American elm’s large leaves, but Wilson said the hybrids are also in demand.

“We’re always trying new things, but we stick with the ones that have proven their hardiness,” he said. “The cold-hardiness becomes a big factor for us, here in Minnesota.”

Wilson said none of his trees have ever had Dutch elm disease, but that could be because trees are generally not affected until they are older.

“As the tree matures, the bark has more crevices for the beetle to hide in,” he said.

When Wilson purchases trees for his nursery, they are typically very young. He then grows them until a harvestable size.

“We plant new trees every year,” he said.

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