Russian olive is a beautiful shrub, but in North America it’s declared unwelcome! This invasive shrub tends to out-compete native plants. In time, entire ecosystems are altered forever. So what makes Russian olive invasive? It hurts the environment!
- Interestingly, regular olive (Olea europaea) is also detrimental to the environment in some areas!
Impact on the environment: severe!
Local fauna and flora are affected by Russian olive as it spreads. This fast-growing plant crowds vegetation out and native plants have trouble germinating, growing, and spreading their own seeds.
Whenever a particularly severe frost spell or dry spell kills native plants off, this hardy and drought-resistant plant bounces back much faster.
Russian olive alters the soil around it
Russian olive tends to alter nitrogen reserves in the soil, fixating it in the roots and wood. This reduces the amounts of nutrients available for other plants who often can’t compete with the newcomer.
It does this by latching a special bacteria to its wide-ranging root system: Actinobacteria frankia. This bacteria captures nitrogen and makes it available to the shrub. It does this so effectively that the amount of nutrients in the soil is altered. Even nearby bodies of water are impacted, and the changes create a favorable environment for water flora-smothering algae.
Outgrowing native plants
Russian olive has been shown to outgrow and crowd out native willow, black cottonwood, poplar, elm, and even other invasive species such as saltcedar (also called tamarisk) and more.
In most cases, Russian olive grows dense and lush and keeps other seeds from germinating under it. Since the canopy of native species are more sparse and let the sunlight through, the following cycle develops:
- Russian olive seeds are brought by animals in their droppings.
- They germinate in part shade provided by native species.
- Russian olive grows and creates an impenetrable underbrush under the native canopy.
- Native seeds don’t have enough light, water and nutrients to sprout and grow.
- As older, taller native trees die off, Russian olive takes up the space.
Native trees are only left with perilous and unstable places to germinate like riverbanks and temporary islands within the riverflow.
Within a couple decades, the flora of an entire area can be replaced.
Russian olive is highly resilient
Russian olive is hardy down to -40°F (-40°C)! It also survives periods of drought and warm to hot temperatures too. It is an extremely vigorous tree that doesn’t have any natural competitors.
To sum it up, Russian olive:
- is very resistant to the cold,
- withstands hot temperatures,
- survives droughts and dry spells,
- grows back vigorously when cut down,
- fends off deer and grazing animals with thorns and spikes.
Additionally, Russian olive berries are prized by many bird species who eat them throughout the winter. Birds then expel the seeds near and far, and these germinate early and grow fast. One single fruit-bearing shrub can thus spread over vast distances.
- Russian olive spreads quickly because animals disseminate it in their droppings.
Fruits of the russian olive tree by Louis under © CC BY-SA 2.0
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