Montana Field Guide

PLANTS: Large shrubs or small trees that grow to 8 meters tall. Stems are thorny with a color and texture that is silvery-mealy becoming orange-brown. Source: Lesica et al. 2012

LEAVES: Alternately arranged. Blades are narrowly lanceolate with smooth (entire) margins, white-mealy, silvery beneath, and 3–10 cm long. Petioles are short. Source: Lesica et al. 2012

INFLORESCENCE: 1-4 stemmed (pedicillate) flowers grow in leaf axils or on short first-year twigs. Flowers have 4-sepals that are silvery on the outside and yellow within, and no petals. Sepals are 2-4mm long. The sepals and stamens form a tube (hypanthium) that surrounds but does not attach to the superior ovary (perigynous). The tube is 5–6 mm long, silvery. The fruit is olive-like, becoming green. Source: Lesica et al. 2012

Fruits mature in late summer.

Russian Olive – Elaeagnus angustifolia, exotic, undesirable, and Regulated:
* Tall shrubs or small trees with twigs that have white-mealy hairs (trichomes), becomeing orange-brown.
* Leaves are alternately arranged, narrowly lanceolate, white-mealy above, and silvery below.
* Twigs have thorns.
* Fruits are silvery-green and dry (olive-like).

American Silverberry – Elaeagnus commutata, native and desirable:
* Shrubs with twigs that have white-mealy hairs (trichomes), becoming gray.
* Leaves are alternately arranged, ovate to elliptic, white-mealy above, and silvery below.
* Twigs lack thorns.
* Fruits are silvery-green and dry (olive-like).

Silver Buffaloberry - Shepherdia argentea, native and desirable:
* Shrubs with twigs that have white-mealy hairs (trichomes), becoming gray.
* Leaves are oppositely arranged, oblanceolate, and white-mealy below.
* Twigs have thorns.
* Fruits are orange to red, juicy berries.

Canada Buffaloberry - Shepherdia canadensis, native and desirable:
* Shrubs with twigs that have brown-mealy hairs (trichomes), becoming gray.
* Leaves are oppositely arranged, narrowly ovate, and brown-mealy below.
* Twigs lack thorns.
* Fruits are orange to red, juicy berries.

In Montana Russian Olive grows in woodlands, thickets, riparian forests, and moist meadows around wetlands in the plains and valleys (Lesica et al. 2012). Plants grow in soils with low to moderate soluble salt concentrations, and are somewhat tolerant of saline soil (Lesica and Miles 2001; Lesica et al. 2012).

GROWTH CHARACTERISTICS
Observations of Russian Olive growing in moist, unshaded areas show it will frequently branch at ground level, only 10-20 cm above the surface (Lesica and Miles 2001). While in drier, shaded habitats plants branch well above ground-level. When damaged Russian Olive plants will sprout from the base.

In a study along the Marias and Yellowstone Rivers in Montana the growth rates of Russian Olive plants increased with age, regardless of age class (Lesica and Miles 2001). The relationship was statistically significant for juveniles, but not for mature plants. Growth rates varied from 0.1 to 2.7 cm per year, averaging 0.8 cm per year. Growth rates were greater on sites closer to alluvial ground water than on higher sites.

Russian Olive is a shade tolerant plant, meaning that seeds germinate and growth continues under shady conditions. Studies of older Russian Olive stands show a diversity in age classes indicating that germination is not driven by a disturbance event, such as is needed for cottonwoods. Its large sized fruits facilitate its establishment in shady and moist sites (Lesica and Miles 2001).

Russian Olive plants fix nitrogen in their roots by forming a symbiotic relationship with bacteria in the genus Frankia (Huss-Danell 1997).

PLANT COMMUNITY DYNAMICS
Montana is near the northern limit of Russian Olive’s naturalized range in North America. Russian Olive plants may affect native successional riparian processes in Montana (Lesica and Miles 2001).

Along the Marias and Yellowstone Rivers, Russian Olive was found to only establish on drier high terraces under the presence of a cottonwood overstory (Lesica and Miles 2001). Russian Olive recruitment appears to be facilitated by established cottonwoods. Speculated reasons include that the cottonwood overstory could make micro-climates more humid and cooler, or cottonwoods might help bring water from the water table up to the upper rooting zone through a hydraulic pump. Once Russian Olive is present observations found it will persist as the mature cottonwoods die out. In the absence of Russian Olive, the native succession would have led to a dominance of sagebrush steppe (Boggs 1984).

Annuals riverine floods deposit alluvial materials and change channel morphology creating new habitats conducive for cottonwood regeneration. Many rivers possess regulated flows hinder cottonwood regeneration, but not for Russian Olive. In Montana Russian Olive plants establish under existing groves of cottonwood, and not in adjacent areas indicating that they can change the riparian community but apparently not its extent (Lesica and Miles 2001).

Ecologically Green Ash (Fraxinus pennsylvanicus) and Russian Olive are similar (Lesica and Miles 2001). Green Ash also reproduces under the canopy of cottonwoods. Based on Montana data Russian Olive grows three times faster than Green Ash (Lesica and Miles 2001). This poses a question of whether Russian Olive can or would outcompete Green Ash in Montana.

ANIMAL INTERACTIONS
Beaver
Beaver may prevent cottonwood from developing a mature canopy of trees adjacent to rivers while not hindering the presence of Russian Olives (Lesica and Miles 2001). In a study along the Marias and Yellowstone Rivers beaver were found to damage 57% and 78% of cottonwood trees, respectively, while only damaging 15% and 18% of Russian Olive trees, respectively (Lesica and Miles 2001). The authors also found cottonwood trees were felled at their base while Russian Olive trees only had 1 or 2 basal limbs removed. Further, beaver damage primarily occurred near to active channels on both rivers. This agreed with another observation that Russian Olive plants lined the riverbanks, while cottonwoods were prevalent at greater distances from the rivers.

Birds
Many migratory birds eat Russian Olive fruits and help disperse these plants. In places where Russian Olive replaces cottonwood, cavity-nesting birds do not appear to use Russian Olive and may lose habitat over time (Lesica and Miles 2001).

Ungulates
The frequency (not quantity) of browsing by native and domestic ungulates on Cottonwood and Russian Olive branches was assessed along the Marias and Yellowstone Rivers (Lesica and Mills 2001). No significant difference in preference between Russian Olive or Cottonwood could be discerned; although, it appeared a higher proportion of browsing was found on Cottonwood trees.

FLOWER / FRUIT
* Flowers are bisexual or unisexual with a single pistil that has 1 style and 4 or 8 stamens (Lesica et al. 2001).
* Flowers on mature plants produce nectar and edible fruits (Lesica and Miles 2001).
* The Fruit is a solitary achene surrounded by the swollen hypanthium base which becomes mealy, and olive-like (Lesica et al. 2001). With maturity fruits become green, ovoid, and 8-15 mm long.

In a study along the Marias and Yellowstone Rivers in Montana Russian Olive generally began producing fruit at the age from 7-10 years (Lesica and Miles 2001). For trees greater than 10 years in age, 89% of them produced fruit. The average age at which Russian Olive plants first become reproductive is at about 10 years. Taking about 10 years to become reproductive, Russian Olive is considered to have a low recruitment rate.

Seeds germinate under a variety of moisture conditions at different times through the growing season (Lesica and Miles 2001). In greenhouse experiments nearly 90% of seeds from Montana plants germinated and emerged within 30 days when buried to one-inch depth (Hybner and Espeland 2014). However, when seeds were buried to depths of three inches, only a few germinated and none emerged from the soil. The study concluded that deeper buried seeds may lose viability or deteriorate from biotic conditions.

Russian Olive will likely continue to increase along Montana’s rivers because it is immune to beavers, is shade-tolerant, and can colonize a variety of moist habitats in the floodplains along our regulated and free-flowing floodplains. It may likely replace cottonwood trees along rivers where overbank alluvial deposition provides the only establishment for cottonwood seedlings (Lesica and Miles 2001). Russian Olive will tend to become dominant in reaches where the riparian zone is less dynamic and the stream is entrenched or channelized (Lesica and Miles 2001). Eradicating mature Russian Olive trees every 10 years or all trees every 30 years could be an effective strategy to control is populations and affects on native wildlife and plants (Lesica and Miles 2001).

PREVENTION
To avoid the development of new infestations Russian Olive should not be planted near to riparian areas, overflow areas, or irrigation ditches (Lesica and Miles 2001).

PHYSICAL and CULTURAL CONTROLS
Revegetation: Russian Olive is invasive, despite that it has a history of being used in restoration and other improvement-type land projects. There are many alternative species that should be used in conservation plantings and readers should consult Species Alternatives for Russian Olive in Conservation Plantings (Tober et al. 2006).

CHEMICAL CONTROLS [Adapted from Piper in Sheley and Petroff 1999]
The herbicide type and concentration, application time and method, environmental constraints, land use practices, local regulations, and other factors will determine its effectiveness and impact to non-target species. Strict adherence to application requirements defined on the herbicide label will reduce risks to human and environmental health. Consult your County Extension Agent and/or Weed District for information on herbicidal control. Chemical information is also available at Greenbook.

Useful Links:
Montana Invasive Species website
Montana Biological Weed Control Coordination Project
Montana Department of Agriculture - Noxious Weeds
Montana Weed Control Association
Montana Weed Control Association Contacts Webpage.
Montana Fish, Wildlife, and Parks - Noxious Weeds
Montana State University Integrated Pest Management Extension
Weed Publications at Montana State University Extension - MontGuides

Russian Olive is an invasive plant that can out-compete many native plants, especially in wetlands, riparian zones, and saline lowlands.

Where flooding is infrequent, Russian Olive plants establish under native cottonwood stands, eventually out-competing them as the stands age.

Stands of Russian Olive can become dense, suppressing understory vegetation.