Noxious Species of the Month

Russian Olive

This month’s invader is a species that can wear two masks, in one area it may be beneficially, while in another it can be horribly destructive. It was originally planted as an ornamental, as many of these noxious species are, but in northeast Wyoming most of this species did not spread widely. It was the few plants that grew by waterways and drainages were we see the species thriving and spreading. Of course I am describing the movement of Russian Olive. This invading tree can be overwhelming one area, and be helpfully in another with only a few miles separating the two stands. In this article, I will discuss the characteristics that will allow you to correctly ID this tree species and then look at some control options for this species when it occurs in select habitats.

Russian Olive is fast growing tree species that usually reaches heights of 15 to 25 feet. Its trunks and branches have large thorns and grow in a twisted irregular fashion. It has long thin leaves that are a chalky green on the top and gray on the bottom. It forms clusters of small yellow flowers that mature to fruits that are olive shaped that first appear gray then turn brown as they mature. It can have growth points on multiple areas on the twisted trunks, which makes control difficult. It was originally planted as a shade tree and in shelter belts for wind and snow protection. This tree is usually identified easily once you become familiar with the species. Hopefully this information along with the pictures provided will help you ID this woody weed.
Russian Olive is a prime candidate for integrated weed management, with each type of control alone will only work for short periods of time, while implementing multiple control types will really help with extended control of this noxious species. Mechanical means of chainsaw, tree shear, or mulcher will remove all above ground growth and will knock back the weed for 2-3 years, but without further treatment the infestation will only become denser in the coming years.

Chemically treatment with a triclopyr (Gralon, Element) herbicide onto the foliage will knock the species back, but in the case of larger infestations the likelihood of covering all foliage is low leaving some of the tree living, which quickly reinfests an area. This also usually takes a lot of herbicide when trying to cover all above ground foliage. Looking at a biological control aspect, there is currently no insect species for release, but some research in Wyoming has shown that goats in high densities can do a good job stopping above ground regrowth on new saplings. All this being considered, in most cases the ideal situation is that you mechanically remove the above ground portion of the tree, apply herbicide to the stumps immediately after cutting or shearing, and then bring goats in the following two summers to prevent new saplings from moving in. Hopefully this gives you an idea of what it takes to get rid of a large stand of Russian Olives, especially ones that are located in a riparian area.

When I talk about Russian Olives with some of our citizens in Campbell County, they begin to worry that I am going to head out to their ranch and make them cut down their shelter belt that has been there for 30 years. In most cases these trees are not an issue when they are on top of hills and ridges away from water sources. Monitoring low lying areas around their ranch is key to make sure seeds haven’t moved to those areas and are starting new infestations. They can stay in that shelter belt for 30 years, but if they get to an area with adequate water, they will spread like wild fire in a short amount of time. This is one of few noxious species that can be beneficial, but if you do find this tree in an area it has not been planted make sure to act quickly as you could have a mess on your hands in a hurry. If you have any questions about this noxious species or any other, please give us a call or stop by our office.