Money may not grow on trees, but those on the Platte River Commons won't grow without it, either.

"The Commons trees are at a tipping point," an arborist told the Amoco Reuse Agreement Joint Powers Board last week.

"Eighty-five percent are in the poor to critical range," Bill Scott said.

That's not counting the 3 percent of the trees that are already dead, in part because of an ineffective drip irrigation system, Scott said.

Scott and Tom Heald of Arboriculture Education Associates reported their findings after the joint powers board asked them to check out the trees' health.

"To be honest with you, it's disheartening," said Heald, an educator with the University of Wyoming's Cooperative Extension Service.

He and Scott conducted a general survey and looked at the trees' structural and projected value, their condition, what was done wrong and how to fix it.

Alice Kraft, director of the Amoco Reuse Agreement Joint Powers Board, said the records of the trees and the irrigation system commissioned by BP during the remediation of the former refinery site are lost.

But lost records don't matter.

"The trees that are there are not going to be sustainable," Scott said.

Too many of a single or a few species will undermine the ability of all trees in an area to thrive, he said.

While native to Wyoming, cottonwoods predominate on the Commons; they, oak and green ash comprise 96 percent of the species, Scott said.

No more than 10 percent of any species should be planted in an area to create sustainability, he said. "When you have one species, you run the risk of prey and disease."

Many trees have both.

Cystopera canker is a fungal disease that chokes nutrients in the limbs, but it usually cannot take hold unless the trees are stressed because of lack of water, Heald said. "You would rarely see this in younger trees."

Oystershell scale insects bore into the bark and suck its nutrients, he said. "They work like a leech."

Many trees also suffer from scorch, the equivalent of sunburn, Heald said. "Scorch is the biggest indicator of a lack of water."

The trees also suffer from damage by construction, poor rangeland soil, grass growing near the trunks and an overall lack of water, he and Scott said.

If tree health wasn't enough to persuade the joint powers board to do something, the economics should, Scott said.

Based on established guidelines, the trees were worth $157,000 when they were planted a half-dozen years ago, and should be worth $300,000 now if they were in perfect condition, he said.

They're now worth $90,000, Scott said.

If the joint powers board turns around the decline, they could be worth $600,000 by 2030, he said. If it does nothing, they'll be worth $7,000, he said.

Heald added, "we're being generous here."

Their suggestion was simple, but costly.

The trees need immediate hand watering as a stop-gap measure, Scott said.

Long term, the joint powers board needs a comprehensive management plan and must replace the entire irrigation system to give deep-root watering, he said.

A new irrigation system will cost close to $500,000, Scott said.

Replacement trees will cost about $500 each, Heald added.

Scott Sissman, chairman of the Amoco Reuse Agreement Joint Powers Board, said the board's executive committee will work on a solution to the problem.

Despite pictures of diseased trees and costs of irrigation, Heald and Scott gave the board some hope.

"By 2014, it can be completely turned around," Scott said.

Reach Tom Morton at (307) 266-0592, or at tom.morton@trib.com. Read his blog at http://trib.com/news/opinion/blogs/morton and follow him on Twitter: @GTMorton

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