Invasive 'burning bush' getting genetic makeover

The burning bush shrub, whose blazing autumn hues illuminate many eastern U.S. landscapes, may soon be getting a makeover to curb its voracious appetite for other plants' land, sunlight and soil nutrients.

After almost a decade of work, a University of Connecticut scientist and his research team have pinpointed the genetic combination to grow a seedless, non-invasive version of burning bush without sacrificing its stunning fall colors and durability.

In short, they've neutered the incorrigible plant to make it behave.

Horticulture experts say the newly published findings by Dr. Yi Li and others at the New England Invasive Plant Center in Storrs could be a boon for landscapers and gardeners, who've pushed annual sales of burning bush — also known as winged Euonymus alatus — past $38 million nationwide.

Those sales figures come despite its listing as an invasive plant in 21 states, and outright sales bans in Massachusetts and New Hampshire. And since UConn will hold the patent with Li, the university also could receive significant royalties if the non-invasive burning bush is a big seller.

"It's a great use of science and a win for everybody if they can take a popular, invasive plant and render it sterile so it's still sellable," said Robert Heffernan, executive director of the Connecticut Green Industries Council. "People do love this plant and they ask for it. That brilliant red color in the autumn makes it look like it's absolutely on fire."

The durable and dense ornamental bush is a popular foundation planting or landscaping border because it thrives in many soils. It also stands up to varying weather, is unfazed by road salt and fertilizer, and is unpalatable to most insects and animals.

But there's a price to pay.

It produces thousands of seeds that easily waft away in the wind, or are carried away by rainwater and birds. Then, they take root in open woodlands and elsewhere. With its thickly matted roots and heights averaging 6 to 9 feet — and up to 15 feet if left unpruned — it makes such dense thickets that other plants have trouble competing for soil and sun.

Burning bush is native to eastern Asia and was introduced in the U.S. in the mid-1800s.

It's now most common in New England and many East Coast states, though it can also be found as far south as Georgia and as far west as Illinois.

Many governments have stopped planting it on state-owned land since its invasive tendencies became evident in recent decades, but earlier plants thrive still along many highways and in open woods where they've taken root.

Li and other UConn scientists have been studying ways to produce sterile cultivars of burning bush since receiving a grant in 2003 from the U.S. Department of Agriculture to start the research.

The work was tedious and painstaking: getting into thousands of the small seeds, removing bits of their tiny nourishing tissue, then treating it with special growth regulators and growing it in Petri dishes. Through trial and error, they finally hit on the right combination.

"It was difficult, but we were confident that it would work and we should not give up," said Li, whose research was published in this month's issue of the international academic journal HortScience.

They've used their findings to grow 12 small sterile burning bush plants so far, though there's no firm estimate on when the research will be used to bring the new cultivar to the widespread retail market.

Heffernan, of the Connecticut Green Industries Council, said the process usually takes a few years.

Many landscapers have skipped burning bush and started using alternatives such as red chokeberry, native winterberry, silky dogwood or native highbush blueberry. And although Massachusetts and New Hampshire ban people from selling or importing the burning bush plant entirely, landowners there are not required to tear out plants already in place.

Until there's a guaranteed sterile version, though, that's exactly what some people are doing.

At the Chicago Botanic Gardens, workers have been removing burning bush plants over the last several years and replacing them with non-invasive plants as the budget has allowed.

Kayri Havens-Young, the gardens' director of plant conservation science, said she was familiar with Li's work at UConn and is excited about its potential as long as the new variety is truly seedless. Just reducing the number of seeds would not be adequate because burning bush's spread is so prolific.

"They're beautiful plants, but they don't stay where you plant them. Unfortunately, they're just not very well-behaved," she said.