Weed & Pest
Re-vegetation after Russian olive removal requires long-term commitment
Douglas – “Controlling Russian olive is not hard,” Joe Scianna, manager and research horticulturist at United State Department of Agriculture Natural Resources Conservation Service (USDA NRCS) Plant Materials Center in Bridger, Mont., said, “It is the treatment afterwards that is the difficult part. It is going to take a long time to ensure that Russian olives do not come back, and people have to be willing to commit to this process.”
Studies conducted by Scianna; Roger Hybner, research agronomist at the Plant Materials Center; Robert Kilian, rangeland specialist in Miles City, Mont.; and Agriculture Research Service staff at Fort Keogh in Miles City concerning re-vegetation after Russian olive removal were presented to land managers at the North Platte Russian Olive Control Workshop on July 30.
“Researchers are still trying to determine the best way to re-vegetate after Russian olive removal in riparian corridors,” Scianna said. “However, the best thing that can be done after removal is follow-up control of the weeds that will inevitably come in, as well as the volunteer Russian olive plants.”
However, replanting native vegetation, such as bur oak, should not be the first thing land managers do after removal.
“Before fretting about replacing the vegetation, it is important to have good control of the weeds,” Scianna continued. “Dense Russian olive stands along rivers and streams suppress a lot of undesirable weeds, and the removal processes and equipment used to remove them create an ideal site for weed invasion.”
“I recommend that the first step taken by land managers is planning a weed control program,” he added. “Over time, probably the second year after removal, managers should think about planting some vigorous native plants to stabilize the site. This is not critical early on, but getting something planted when the weeds are under control is important. Just remember, this is a long term, slow fix.”
Managers will see volunteer Russian olive plants years after the mature trees have been removed.
At a seed storage facility in Sheridan, seeds stored in less than 70 degree temperatures with very little humidity still had a 77 percent germination rate after 28 years in storage.
“We assume that when Russian olive seeds are in the soil, they have a 20 year or better lifespan,” said the research horticulturist.
In his studies, Scianna investigated rooting depth in relation to transplant success in cottonwood trees. It was found that trees grown in 24- and 36-inch-deep pots had greater survival rates and earlier growth than seedlings grown in conventional 10-inch-deep pots.
In the presentation, data showed that trees with 36 and 24 inches of root had a 100 percent survival rate, while those with 10 inches of root had only a 67 percent survival rate.
Proper preparation of the pots is also imperative for the survival of the plant.
“When filling the pipes with soil, it is important to tamp the dirt down,” Hybner said. “Otherwise, there will be an air pocket in the middle, and it does not do the root any good to be growing in an air pocket.”
Care of the seedling after planting is also important.
“One of the biggest things a land manager can do for a tree is keep the area clean around it for at least the first three to five years,” Hybner continues. “This reduces competition for nutrients.”
The Montana-Wyoming Plant Materials Center is also currently looking at the impact of root length on bur oak survival and growth on dryland sites. This is the first year in the study, so no data is currently available.
USDA Natural Resources Conservation Service Plant Materials Center Manager Joe Scianna said bur oak growth is initially quite slow, so they are looking to see if plants will grow faster if they have long roots when first planted.
“Bur oak is a great native plant, but for the first three to five years, they do not display much height growth because all of their energy is going into developing a long taproot,” he said. “Most producers are not impressed with this when they consider using the plant as a windbreak. By cultivating them in the deep pots, we hope to circumvent the lag time in height growth.”