Threat of ban provokes need for sterile shrubs

March 14, 2011
Common cherrylaurel produces fragrant small white flowers and purple-black fruit in great numbers. (Photo by Ryan Contreras)
Common cherrylaurel produces fragrant small white flowers and purple-black fruit in great numbers. (Photo by Ryan Contreras)

CORVALLIS, Ore. – Popular non-native bushes and plants that grow aggressively and are considered to be invasive could eventually be replaced with their sterile offspring, thanks to an Oregon State University breeding program.

To help control invasive species such as the butterfly bush (banned in Oregon in 2010), Ryan Contreras and members of his lab at Oregon State University develop varieties of plants that have less potential to become invasive. For one popular landscape shrub, the cherry laurel, they hope to develop sterile varieties within five years. Oregon nurseries will evaluate the varieties, which would be available to consumers shortly thereafter.

Contreras hopes that the sterile varieties of cherry laurel will not produce fruit. "This would be good news for Oregon nurseries because they are required to hand strip fruit from plants that are shipped to California," he said. Fruitless varieties also won't attract another invasive species – the cherry fruit fly.

Oregon nurseries are a key component in the breeding and introduction process, Contreras said. "Their collaboration to evaluate how well the new varieties grow is indispensable."

The cherry laurel has been reported to be invasive, Contreras said. "That means it may have the potential to form monocultures and squeeze out neighboring native plants." Birds compound the problem when they eat the fruit and drop seeds into natural areas.

Homeowners like to grow cherry laurel in their yards as evergreen hedging and screening, Contreras said. The most popular variety, called 'Otto Luyken', is a bush that grows six to eight feet tall and produces a stalk of fragrant small white flowers and a purple-black fruit that looks like a berry, called a "drupe," with a hard pit like a peach.

"Within five years, we hope to have identified sterile forms and be in an evaluation phase," Contreras said. One technique his lab uses to breed sterile hybrids is to manually pollinate flowers of Portuguese cherry laurel with pollen from common cherry laurel, and vice versa. The hybrids will be observed at Oregon State University growing facilities for several years to identify promising varieties.

"We design our research program to help Oregon growers who want to create excitement and market what's new and hot," Contreras said. Growers also want people to know that in addition to the aesthetics of nursery crops, landscape plants contribute ecological benefits, such as erosion prevention and storm water treatment.

Contreras also works with a nonprofit national research institute, the Landscape Plant Development Center, which has research facilities in Minnesota as well as a 24-acre site in Aurora, Ore., donated by the J. Frank Schmidt and Sons Nursery in 1999.

In addition to his work on breeding for non-invasive varieties, Contreras conducts programs at OSU and the Center in Aurora to breed plants for water efficiency, disease resistance, aesthetics, texture and fragrance.

The downturn in the housing market has had a direct impact on the nursery industry and the amount of nursery stock sold, said Gary McAninch of the Oregon Department of Agriculture. Nursery and greenhouse crops make up 13 percent of the total agricultural commodity sales in Oregon, and sales were $562 million in 2010.

Author: Judy Scott
Source: Ryan Contreras