Supposedly sterile olive trees trying to go forth, multiply

Monday, May 3, 2004 | 11:27 a.m.

The Clark County School District has a horticultural mystery to solve.

At Leavitt Middle School on Lone Mountain Road, 33 olive trees have pollinated and produced fruit -- even though they were guaranteed to do neither.

In 1990, in an effort to reduce the airborne pollen that triggers seasonal allergies for tens of thousands of residents, Clark County banned the planting of "olea europaea," the common European olive tree, as well as fruitless mulberry trees.

Producers of two patented varieties of olive trees, the Swan Hill and the Wilsoni, applied for exemptions to the statute and are on the county's list of approved trees.

Both varieties produce less than 15 percent of the pollen of the common European olive tree, as required by county statute.

Invoices for the landscaping at Leavitt show the district bought Wilsoni olive trees, said Robert Folle, compliance manager for the Clark County Department of Air Quality Management.

For now the air quality management department has made no finding of fault, Folle said.

"All of our information shows the correct trees were ordered from a certified nursery," said Folle, who is investigating after an area resident complained to the county about the trees. "At this point we don't know if we're dealing with some sort of mutation or whether the wrong trees went in to begin with. We've talked with the growers, and for some reason an unknown number of the trees fruit and pollinate anyway."

Complicating the investigation is the fact that the air quality department doesn't have a biologist or horticulturalist on staff to inspect the trees, Folle said. The engineered varieties appear identical to the regular olive trees, Folle said.

That makes it difficult to tell -- without a laboratory test -- whether the correct trees are being planted, Folle said. It has been suggested that the county simply ban all olive trees outright to avoid confusion, Folle said.

"We have so many landscapers opening up shop all the time, a lot of them don't know what the rules are," Folle said. "They go to California or Arizona for their supplies and we don't know what they've planted until it's already in the ground."

David Karnosky, a forest geneticist and professor at Michigan Technological University, said if the Wilsoni trees were grown using grafts, it's possible that the root stock overtook the top of the trees. But it's unlikely to happen to a large group of trees planted together, Karnosky said.

"It's much more likely a mistake was made in the nursery, either in the cultivating of the trees or in what was delivered," said Karnosky, who clones and cultivates poplar trees as part of his research. "The thought of 33 trees all throwing back is pretty wild."

Trees have genetic markers and it would be possible with a laboratory test to determine whether a tree is a common European olive or another variety, Karnosky said. The cost of such a test would probably vary from no charge to several thousand dollars, depending on whether or not a laboratory was already set up to handle the request, Karnosky said.

When Leavitt was built in 2001, some area residents were upset at having a school in their neighborhood, said Alan Paulson, coordinator of landscaping and grounds for the school district. To appease their concerns about appearance the district promised to provide extensive foliage, Paulson said.

That required the district to look for trees that would grow larger than those used at a typical school site, and the contractor handling the grounds recommended the Wilsoni, Paulson said.

If the air quality department demands the trees be removed it could cost the distict upwards of $60,000 to remove the existing trees and buy and plant new ones, Paulson said. If it turns out the contractor or the supplier made a mistake, the district will seek to recover its costs, he said.

There have been no problems reported with trees planted at other school sites, Paulson said.

The dropped fruit around Leavitt proved tantalizing to students, who used it to scrawl graffiti on the school building, steps and walkways, said Patrick Hayden, the school's principal.

The district has since sprayed the trees to discourage fruiting and pollination, Hayden said.

"We told our students to stop and we haven't had a problem since," Hayden said. "The trees are really beautiful; I hope they don't have to pull them out."