Elaeagnus umbellata (autumn olive)

E. umbellata is a deciduous shrub which has been introduced from its native Asia to Europe and North America for revegetation, wildlife cover and environmental benefits, but in many areas it has escaped and become naturalised and invasive especially in disturbed sites and areas near cultivation. Due to its high seed production and high germination rates, this species has the potential to rapidly colonize new areas. Additionally, it is a hardy, nitrogen-fixing species that resprouts quickly after burning or cutting. This species has become particularly invasive in central and northeastern states of the USA and it is beginning to spread across Europe. Currently, E. umbellata is considered one of the most troublesome invasive plants in central and eastern USA (USDA-NRCS, 2016). It is related to other invasive species Elaeagnus angustifolia and Elaeagnus pungens, the former being a serious weed in western North America.

Elaeagnaceae is a small family of flowering plants including just 3 genera (Elaeagnus,Hippophae and Shepherdia) and about 45 species of thorny and mostly deciduous shrubs and trees native to temperate regions of the Northern Hemisphere, Malesia and Australia (Zheng et al., 2006; Stevens, 2012). All genera are associated with nitrogen-fixing actinomycetes of the genus Frankia in their roots (Stevens, 2012).

E. umbellata is a deciduous shrub 2-4 (-5) m tall and 10 cm in diameter with slender, spreading branches, more or less spiny with thorns about 2.5 cm long. The bark is removable in longitudinal strips exposing the white hardwood underneath. An important distinguishing characteristic is that shoots and young branches are clothed with very attractive white silvery scales (lepidote), but which disappear with the rains. Leaves in clusters, elliptic to ovate-oblong, 4-8 cm long and 1-2 (-2.5) cm wide, upper surface sparsely white and covered with small scaly leaves (lepidote), lower surface densely white lepidote, apex acute to sometimes obtuse, petioles 0.5-1 cm long, densely white lepidote. Fragrant flowers appear in bunches of 1-7 in axillary umbels, white to light yellow, 8-9 mm long and 7 mm in diameter, perianth densely scaled, four-lobed; androecium comprising 4 stamens, very small, attached to the mouth of the corolla tube; gynoecium, simple, with one pistil, its average length being 7 mm, pedicels 3-6 (-8) mm long, elongating up to 12 mm long in fruit; hypanthium slender, gradually narrowed at base, 5-7 mm long; calyx lobes narrowly ovate, ca 3-5 mm long. Fruits, ovoid to globose, 3-9 mm long and 5 mm broad; epicarp, thin, covering the whole fruit; mesocarp, pulpy and juicy; pedicel, 5-6 mm long; freshly picked fruits, coral pink, seeds, 7-8 mm long and 2-3 mm in diameter, saffron yellow and approximately 26 mg in weight. Adapted from PIER (2008) and Parmar and Kaushal (1982).

E. umbellata is native to tropical and temperate Asia, from Afghanistan to Japan, traversing northern India and northern China. It is sympatric with other Elaeagnus species such as E. angustifolia, but tends to occupy different habitats. It has been introduced in North America, Europe, and Australia (USDA-ARS, 2016). 

E. umbellata was introduced intentionally to temperate regions in Europe and North America. It was first introduced to the UK in 1829 (Bean, 1973). It was introduced into the USA in 1830 from China and Japan (Sather and Eckardt, 2001). It has been actively promoted by state and federal agencies for shelter belts, erosion control, strip mine reclamation, wildlife habitat, and was widely marketed as an ornamental. The shrub has now become a noxious weed and invasive species in many states from the east coast to the central prairies. This species is also spreading across Europe.  Currently it is listed as invasive in France, Italy, Belgium and the Azores (Christenhusz and Uffelen, 2001). It does not appear to be invasive in the UK, where it was not recorded in the wild until nearly 150 years after introduction, and did not naturally regenerate in trials where it was used as a nurse plant for walnut (Clark et al., 2008). In Costa Rica it can be found naturalized and spreading in disturbed sites, thickets, and along roadsides (Christenhusz, 2009). 

The risk of new introductions of E. umbellata is very high. This species is listed as invasive in the USA (USDA-NRCS, 2008) and Europe (DAISIE, 2016) and it also received a high score in a weed risk assessment for the Pacific (PIER, 2008). It could become an invasive weed in other temperate areas where it is not yet present, such as parts of Australia, New Zealand, South Africa and South America. Further introductions in Europe should also be monitored, as well as habitats at risk where already present.

E. umbellata is known to invade pine plantations in the USA.

E. umbellata is closely related to another Asiatic native, E. angustifolia, which is also invasive in the USA. E. angustifolia leaves remain silvery until the leaves are shed in autumn, while in E. umbellata the silvery scales which cover young leaves in spring wear off during the summer so that the leaves turn greener.

In its native range, E. umbellata can be found in thickets, sparse woods, forest edges, hillside wastelands, riversides and seashores in subtropical and temperate regions of Japan, Korea and China at elevations of 20 to 3000 m. It is common in humid temperate areas with 1000-4000 mm annual rainfall in Japan, but it can grow even in semi-arid areas of Nei Menggu, Gansu and Shaanxi, China, where annual rainfall is around 400 mm.

Outside its native range, it can be found naturalized in disturbed sites, thickets, along roads and also planted in gardens and parks (Christenhusz, 2009; USDA-NRCS, 2016). In North America, typical habitats include disturbed areas, roadsides, pastures and fields and it invades grasslands and sparse woodlands, pine plantations, ravines, grazed upland oak forest, and the edge of hill prairies in Illinois and central USA (Ebinger and Lehnen, 1981; Owens and Cole, 2003). In New England, USA, it is found on abandoned fields, abandoned gravel pits, early-successional forest, pasture, planted forest, railways, roadsides, paths, urban areas, and is probably most prolific on disturbed or ruderal sites (Munger, 2003). In southern Ontario, Canada, it is found in dry to mesic sandy, forested and open to sparsely shaded habitats, though is most invasive in areas of dry sandy soils and is generally not invasive on fine-textured, periodically wet soils (Catling et al., 1997). Its shade tolerance is disputed, being reported various as shade intolerant or tolerant, though it appears that it has at least some ability to establish under a forest canopy but is not well-adapted to low light conditions as it is generally absent from dense forest and restricted to open-canopy areas (Munger, 2003). PIER (2008) noted it as dominating in almost any landscape type, from fencerows to meadows to open woods, even sand dunes and mine spoils. Munger (2003) noted special risks for natural communities of sandy, infertile habitats throughout the Great Lakes region.

The species-specific rust Aecidium elaeagni-umbellatae was found attacking E. umbellata in China (Huang et al., 2004). This and further pests and pathogens from the native range could be tested as biocontrol agents. Zheng et al. (2006) report that 10 fungi have been found on members of the genus Elaeagnus, including Aecidium elaeagni which may be host-specific to Elaeagnus spp. and Septobasidium albidum which has a host range that includes E. umbellata as well as species in other genera. Also, 22 arthropods belonging to 10 families of five orders are reported, and the moth, Teia prisca may be specific to E. angustifolia. All natural enemies are listed along with whether they are known to attack the three main invasive Elaeagnus spp., E. angustifolia, E. pungens and E. umbellata.

In Ontario, Canada, use of E. umbellata as a nurse tree for walnut had mixed effects, as analysis found “generally better walnut growth when interplanted with other woody species, but autumn olive (Elaeagnus umbellata), the species that stimulated the best walnut growth, grew invasively throughout the study area, thus ruling it out as a nurse species” (Pedlar et al., 2006). Costs for control are not known.

E. umbellata grows vigorously and is competitive against native species, growing rapidly into impenetrable, thorny thickets, suppressing and/or displacing native and/or more valuable species and supplanting native habitat. Due to nitrogen-fixation, it can affect nitrogen cycling and availability in soils (Baer et al., 2006), and this may adversely effect native communities that may depend on infertile soils. There are also probable allelopathic effects from leaf litter on emergence of seedling of native tree seedlings in central USA (Orr et al., 2005).

Many studies have been undertaken in Illinois, USA. Woody plant invasions including E. umbellata, Rosa multiflora and Ulmus pumila exceeded 6500 stems/ha in successional old fields, and greater than 16,500 stems/ha in sown tallgrass prairie (Zimmerman et al., 1993), with Munger (2003) presenting data showing E. umbellata densities of 5225 stems/ha in pine plantations, increasing to almost 34,000 33,975 stems/ha in a hardwood ravine and almost 68,000 stems/ha in an oak (Quercus spp.) forest. Densities of 125,000 stem/ha were recorded in the understorey of a yellow-poplar-sweetgum plantation from nearby plantings in the early 1970s (Munger, 2003). Yates et al. (2004) found densities of three invasive plants, E. umbellata, Lonicera japonica and Rosa multiflora were up to 180,000 stems/ha, but only E. umbellata was established in both interior and edges of study sites and as such, E. umbellata posed the most ecological damage because it is well established throughout and should be given a high priority when implementing management and control efforts.

The only social impacts are positive, such as from the aesthetic value as an ornamental species.

E. umbellata can fix nitrogen and it is tolerant to salt winds, this species is therefore used for fixation of coastal sand dunes in Japan, and is frequently planted mixed with Pinus thunbergii as a soil improving tree. E. umbellata is also planted in eroded areas of mountainous zones to re-establish and develop vegetation. In China it is occasionally cultivated in gardens (Zhang, 1997). The wood is not valuable. The fruits are sweet to acidic and are good to eat along with its seeds, having a good keeping quality and can be stored up to 15 days at room temperature, rich in protein and their use should be encouraged. The fruit are eaten in India, with a single bush yielding about 650 g of fruits in 2-3 pickings (Parmar and Kaushal, 1982). Medicinal products are used in China to treat asthma, diarrhoea (Uehara, 1977), and other plant parts having various additional uses such as pulmonary infections and in cardiac ailments.

E. umbellata was being promoted in North America until recently for the purpose of attracting wildlife, and due to its drought and disease resistance and tolerance of poor soil, it has also been widely planted on poor sites and roadsides to prevent soil erosion. It is also being promoted as a possible source of pharmaceutical compounds, as the edible fruit is exceptionally high in the antioxidant carotenoid lycopene and several other carotenoids, and lycopene has been associated with prevention of certain chronic diseases including prostate cancer (Fordham et al., 2003). Naturalised populations were assessed for their potential to supply fruit for nutraceutical use and could be a commercially viable crop, especially on low-fertility and sandy soils that may be unsuitable for other agricultural uses (Black et al., 2005). The plant is very ornamental because of its silvery foliage and flowers. It is a very hardy plant and grows successfully under dry conditions. It can therefore, be planted as a protective hedge around fields as a well as around houses and gardens.

E. umbellata has been promoted as a beneficial wildlife species and was widely planted in wildlife management areas in the USA as an important wildlife food during periods of seasonal food scarcity, fruits consumed by a variety of wildlife, including very many different birds, raccoons, skunks, opossums and black bears and white-tailed deer browse the foliage (Munger, 2003).