The hybrid A. x prunifolia is a shrub with attractive white flowers and purple fruits that can spread vegetatively as well as by seed. It originated in North America and is now grown widely as an ornamental in other parts of the world. It h...
The hybrid A. x prunifolia is a shrub with attractive white flowers and purple fruits that can spread vegetatively as well as by seed. It originated in North America and is now grown widely as an ornamental in other parts of the world. It has not been widely reported as an invasive species, but Wiegers (1983; 1984) describes how it has spread rapidly in Phragmites australis reed beds in the Netherlands since 1900. Ozinga et al. (2007) record it among the small number of invasive plant species in the Netherlands. It shows invasive tendencies in Latvia (Rutkovska and Jursevska, 2008), is listed as an agricultural weed in Canada (Darbyshire, 2003), as a ‘garden thug’ in the UK (Clement and Foster, 1994) and as a threat to grasslands in Australia (Barker et al., 2006). It is a black-listed species for Norway (Gederaas et al., 2007). It appears in global lists of environmental or invasive weeds (e.g. by Cronk and Fuller, 1995), and clearly has the potential for invasive behaviour. Being widely grown as an ornamental is a further cause for concern.
Aronia x prunifolia is a natural hybrid between Aronia melanocarpa and Aronia arbutifolia (Wiegers, 1983; USDA-ARS, 2009). It has been placed in various other genera, including Crataegus, Aronia, Mespilus, Sorbus and Pyrus (IOPI, 2009). USDA-NRCS (2009) and Phipps (1989) refer to it as Crataegus persimilis Sarg.; others, including Weakley (2007), as A. prunifolia. Not all sources equate C. persimilis or Crataegus prunifolia with A. x prunifolia. IOPI (2009) fails to suggest the synonymy and further equates only certain C. prunifolia (with authorities as in the Identity section of this datasheet) with C. persimilis. Weakley (2007) recognises that the taxon is a hybrid, but because of long establishment and ability to reproduce freely, suggests it be treated as a species – A. prunifolia (Marshall) Rehder. A number of horticultural variety names are listed by different horticultural suppliers.
A. x prunifolia is a rounded shrub or small tree, 2 to 4 m high with erect stems. It can spread vegetatively by suckers from the base. The leaves are alternate, simple, oblanceolate to obovate, 8-10 cm long, bright green above, paler and moderately pubescent below, turning bright red at the end of the season. The inflorescence is a corymb of 10-25 flowers, each about 1 cm across with five sepals and five white petals. Stamens white, numerous. The ripe fruits are dark purple, 7-12 mm in diameter. There are one to five seeds per fruit of the parent species of A. x prunifolia, which are flattened, broadly crescent-shaped, and amount to about 600,000 seeds per kg (about 2-3 mm long) (Gill et al., 2008). Presumably the seeds of A. x prunifolia are similar.
USDA-ARS (2009) indicates quite wide distribution for A. x prunifolia in eastern USA and Canada. USDA-NRCS (2009) does not list A. x prunifolia and gives a much more restricted distribution for Crataegus persimilis in northeastern USA and just Ontario in Canada. These are generally regarded as synonymous, but there is perhaps some confusion of identity here.
Its distribution as an ornamental plant is certainly very much wider than is indicated in this datasheet. It is widely grown as an ornamental and almost certainly occurs in most, if not all, European countries and many of the states of USA and Canada not listed here, and in the more temperate countries of Asia (there are local names in Korea and China). However, information on its distribution is not readily confirmed.
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
It is believed to have been introduced to Europe from North America before 1700. Preston et al. (2002) recorded that it was introduced to the UK by 1791 and first noted in the wild in 1934. The first specimens recorded in the Netherlands are from 1875 (Wiegers, 1983) and it has spread rapidly in reed beds there since 1900. No other records have been located on the history of its spread outside the USA.
The risk of introduction is clearly very high considering its widespread availability as an ornamental. However, it has probably already been introduced to most countries with a suitable climate and the main risks are from escape from cultivation and naturalization, as has apparently occurred in the Netherlands.
In the Netherlands, A. x prunifolia forms a dense scrub in Sphagnum bogs, Phragmites reed beds and in species-poor marshy Betula woodland along with Alnus glutinosa (Wiegers, 1984; Sýkora, 2006; W Tamis, Institute of Environmental Sciences, University Leiden (CML), The Netherlands, personal communication, 2009). Apart from growing in bogs, it occurs along forest trails, in heather (often in the vicinity of estates), scrub and woodland edges. In the UK, it is recorded from woodlands, plantations, hedgerows, parks and roadsides (Preston et al., 2002).
Chromosome number of both the parents of A. x prunifolia i.e. Aronia melanocarpa and Aronia arbutocarpus, is 2n=34. It is possible that the hybrid is an allotetraploid, but this has not yet been confirmed (W Tamis, Institute of Environmental Sciences, University Leiden (CML), The Netherlands, personal communication, 2009).
It is not clear to what extent this hybrid arises in the wild. It seems likely that most, if not all, of the plants in cultivation originate from North America although new hybrids are known to have been created by horticulturists. The fact that plants can be grown from seed and that it breeds true and appears stable suggests that the original hybridization took place a long time ago (VanDusen Botanical Garden, 2009). In the wild, it spreads both by seed and also from suckers from the roots. In cultivation, it may also be propagated vegetatively from cuttings or grafting. The flowers are fragrant and attract bees and butterflies, and are presumably cross-pollinated, although at least one of the parents (A. melanocarpa) is described as self-pollinated. The seeds need stratification (exposure to low temperature (1-50C for 40-60 days) before they will germinate (Gill et al., 2008). Germination can occur at a range of pH values from 3 to 7 and the pH of ground water at sites in the Netherlands infested by the weed may vary from 3.3 to 6.3 (Wiegers, 1984).
Physiology and Phenology
A. x prunifolia is a typical temperate perennial, losing its leaves in winter, re-foliating and flowering in the early spring and flowering from April to July in the USA, fruiting from August to October. The fruits persist into mid-winter, but not much longer. Studies in the Netherlands showed plants up to at least 13 years old (Wiegers, 1984).
Wiegers (1984) recorded some correlation with high ammonium levels (1-4.5 mg/l).
In the Netherlands it is associated in the wild with Betula, Alnus, Phragmites and Sphagnum. Wiegers (1984) described a range of associations on infested sites in the Netherlands.
A. x prunifolia is a typical deciduous temperate plant being frost-hardy, and requiring stratification for germination. Although it is recorded from very wet, acid Sphagnum bog situations in the wild, it is curiously also able to survive in quite dry, well-drained situations and is recorded as drought-tolerant and suitable for ‘xeriscaping’ as an ornamental (Dave’s Garden, 2009). It prefers full sun or only partial shade.
It tolerates a wide range of pH from highly acidic (pH 3.3) (Wiegers, 1984) to slightly alkaline (pH 7.8) (Dave’s Garden, 2009).
Wiegers (1984) recorded that it is found over a wide range of conditions from more or less oligotrophic to slightly brackish and moderately eutrophic conditions.
In the USA, it is regarded as hardy in USDA Hardiness Zones 4a (minimum temperature -300C) to 8b (minimum temperature - 90C) (Dave’s Garden, 2009).
A. x prunifolia has few serious natural enemies, but there is some susceptibility to leaf spots and twig/fruit blight (Kemper Center for Home Gardening, 2009). It can also be host to mistletoe Viscum album (Barney et al., 1998).
A. x prunifolia is listed as an agricultural weed in Canada, although it is not clear what crops are affected (Darbyshire, 2003). It is also listed as a threat to Australia’s grazing industries (Barker et al., 2006).
In the Netherlands, A. x prunifolia has invaded Sphagnum bog and Phragmites reed beds, modified the habitat and threatened a variety of native species. Occurrence in reed beds interferes with normal mowing management and ‘under its rapidly spreading canopy nearly all other species become suppressed, and the characteristic reed marsh vegetation is in imminent danger of disappearing’ (Wiegers, 1983).
Impact on Biodiversity
In the Netherlands, A. x prunifolia has invaded Sphagnum bog and Phragmites reed beds, modified the habitat and threatened a variety of native species (Wiegers, 1983; W Tamis, Institute of Environmental Sciences, University Leiden (CML), The Netherlands, personal communication, 2009).
Apart from its value as an ornamental, the fruit of A. x prunifolia is high in vitamin C and exceptionally high in antioxidant phytochemicals, especially anthocyanins; all members of the flavonoid category of antioxidant phenolics. The berries can also be eaten fresh, but are very astringent and bitter and are mainly used in jams, jellies, wine and juice (Dave’s Garden, 2009; Fruit Bearing Trees, 2009).
The rich antioxidant content of Aronia spp. may be beneficial as a dietary preventative for reducing the risk of diseases caused by oxidative stress. Preliminary results show benefits of Aronia anthocyanins in colorectal cancer, cardiovascular disease, chronic inflammation, gastric mucosal disorders (peptic ulcer), eye inflammation (uveitis) and liver failure (Wikipedia, 2009). These results probably refer to work with the parent Aronia species, but seem likely to apply also to A. x prunifolia.
Aronia arbutifolia (‘red chokeberry’), one of the parents of the hybrid A. x prunifolia, differs in having leaves densely pubescent beneath, sepals glandular, and red berries. The other parent, Aronia melanocarpa (‘black chokeberry’), is a smaller shrub, rarely exceeding 1 m, with smaller leaves, glabrous beneath, larger flowers that are 1.5 cm across, glabrous sepals, and black fruits.
Weakley (2007) noted that these three Aronia taxa are distinguished from other Crataegus by the dark trichomes on the upper midribs, especially towards the base of the leaves. Unlike Crataegus they do not have spines.
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
In the Netherlands, mowing, burning and grazing have been used for control, but no detail is available.
There are no reports of chemical control of this species, but Aronia melanocarpa is noted as susceptible to 2,4-D, dicamba and picloram (Benton District Soil and Water Conservation, 2009).