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Wisconsin Plant of the Week

Elaeagnus umbellata Thunb.

Elaeagnaceae (Oleaster Family)

Common Name:

autumn olive

10/02/2000

Autumn olive is a deciduous shrub or small tree to 5 m tall thatís been introduced as a landscape shrub and become naturalized in fields and sparse woodlands after disturbance. It threatens natural  communities by creating heavy shade, similar to that of buckthorn, which outcompetes native vegetation.

Fragrant pale yellow flowers bloom along last yearís twigs after the leaves emerge in spring. Flowers have with 4 petals with a floral tube about 1 cm long. Leaves are alternate, broadly elliptic, with smooth edges, a green upper surface and silver-white scales underneath.  The twigs are dotted with rust colored scales. The juicy palatable fruits are pink to red, also dotted with scales, and hang on stalks about 1 cm long.

Like in the legumes, certain soil bacteria induce nodules on the roots of Autumn olive.  The bacteria living in the nodules fix nitrogen from the air, which the plant can use, allowing it to thrive in poor soil.

Autumn olive has many characteristics of ecological invaders -- it grows rapidly in all soil types, tolerates a wide range of moisture conditions, sets a lot of seed with a high germination rate and which is transported by birds. It also spreads by sprouting vigorously after cutting or burning, so effective management requires cutting the stem and applying a herbicide like glyphosate.

It was introduced to the eastern US in the 1930ís and by 1970 had spread to Chicago, both naturally and by intentional plantings for wildlife forage and re-vegetation. Over the past 20 years itís become more common in Wisconsin, especially the southern counties, so that itís now a significant threat to natural communities.

The Oleaster family is a small family of shrubs and small trees, all with silver or rust colored scales or hairs on leaves, twigs and buds.  We have two similar genera: Shepherdia (buffalo berry) has opposite leaves and flowers with 8 stamens; Elaeagnus, has alternate leaves and flowers with 4 stamens.

  • Origin of the name: Elaeagnus, Gr., elaion, olive oil; umbellata, L. umbel, may refer to the flower cluster
  • Range:  Native to e. Asia; now in US, from ne, s to GA, w to WI, KY
  • WI Range:  Throughout southern WI, spreading north
  • Common associates: Common milkweed, gray dogwood, redtop grass
  • Wetland Indicator Status: (FACU)
  • Coefficient of Conservatism: C = * (S&W), C = * (MI)
     
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