Once desirable ash tree now urban pariah

Not so long ago, ash trees topped the list of preferred trees in communities all over the Twin Cities. Tough, fast growing and beautifully shaped, they were the landscaper's darling.

Then came the emerald ash borer, which is expected to kill millions of ashes in Minnesota.

Now, Bloomington is about to add the beleaguered ash to the same list of prohibited trees that includes invasive buckthorn and the female ginkgo biloba tree, which bears fruit that smells like vomit or feces.

The city's Planning Commission will take up the issue tonight. It is expected to go to the City Council in July.

"It just makes sense," said Bob Hawbaker, city planning and economic development manager. "This is one of those 'well, duhhhhh!' ordinances. One hundred percent of the ash trees are going to be dead."

The discovery of the borer in a St. Paul neighborhood three weeks ago has hastened the ash's fall from preferred urban tree to pariah. Though individual trees can be effectively treated with chemicals to prevent them from dying, treatment is expensive and must be given year after year.

Experts hope a stingless wasp that is a natural enemy of the borer eventually can be used as a control. That's being tried in Michigan. But if a wasp release happens here, it is likely a year or more away, said Geir Friisoe, plant protection division director for the Minnesota Department of Agriculture.

Hawbaker said Bloomington is moving now to limit damage in the city. He takes no joy in the action and says he has an ash tree outside his own home that he would hate to lose.

"This is just one of those clean-up ordinances," he said. "There isn't a landscape installer or architect that will put up an ash tree now."

Aimed mainly at developers

Though Hawbaker said the city's ordinance is intended mainly to make sure invasive, messy and dangerous trees aren't planted in new developments, it affects homeowners too. It says simply that "it shall be unlawful to plant any of the following trees within the City of Bloomington." Besides two types of buckthorn and the stinky gingko, trees on the list are boxelder (which is weedy), Eastern cottonwood (brittle, with woolly seed masses that can clog screens and machinery vents) and Lombardy poplar (short-lived and prone to disease).

A homeowner who planted one of those trees could be told by the city to remove it. But most nurseries have stopped selling ash trees anyway, and no one from the city is driving around to see what kind of trees people are planting, said Bloomington city forester Paul Edwardson.

Many cities have similar regulations, though lists of preferred trees are more common than prohibited ones. Woodbury specifies 21 tree varieties that are permitted in new developments; ash trees were removed from that list three or four years ago. In Apple Valley, boxelders, poplars, willows and silver maples are not permitted to be planted as replacement trees. In Edina, cottonwoods are not supposed to be planted anywhere in the city, and evergreens, boxelders and silver maples are barred by ordinance from boulevards.

'My American right?'

As a commercial landscape contractor and tree grower, Dave Kleinhuizen says trees are his passion. The owner of Margolis Co. of Roseville understands but also resents the restrictions cities put on tree planting. Cities, he said, are haunted by their experience with Dutch elm disease.

"Cities don't want the cost of [tree] removal down the road," he said. "But hey, if it's my property and it's my tree, shouldn't I be able to do with it what I want if I'm willing to inject my tree to try to prevent emerald ash borer? Isn't that my American right to do so?"

Kleinhuizen still has ash trees growing on his farm, and he said some landscape designers still ask for them. Though many cities stopped planting ash trees years ago as they watched emerald ash borer creep ever closer, Kleinhuizen said he sold ash trees to contractors as recently as 2007. Bachman's, which stopped producing ash trees in 2002 but sold them by special order until this year, discarded its remaining stock when the borer was discovered.

Arborists say diversity will be the key to trying to replace ash trees in the urban forest. Ironically, ashes -- which were planted in large numbers along boulevards as replacements for elms that were ravaged by Dutch elm disease -- could be replaced by disease-resistant elms.

"We're going to see the transition back to elms," Kleinhuizen said. "There are some fantastic American elms that have come through breeding programs."