(Sorbus aucuparia)

European Mountain Ash, fruiting in its third year after planting

Cultivar tested

‘Rabina’

Description and site preference

Type and size – Oval or round tree, 20-40 feet
Hardiness zone – 3-7
Exposure – prefers full sun
Soil – loams, pH 4.5-7.0
Drainage – well-drained

Economic factors

Years to harvest – 2-3 years
Maintenance – minimal, remove suckers
Life of planting – 50+ years
Machine harvest potential – low to none
Suitable markets – too astringent for most markets

Dormant European Mountain Ash (note upright growth habit and suckering tendency)

Notable features

Nutritional highlights – While parts of the plant, including the fruit, have been used in folk medicine to treat colds, diarrhea and other minor health issues, there are toxicity concerns with the raw fruit
Adaptability – somewhat limited by soil and moisture needs
Pest issues – subject to fire blight that can be spread to other species
Invasive potential – not considered a threat
Environmental benefits – food for wildlife

Integration characteristics

Shared management – intermediate, similar to other tree species
Shared equipment – low, concern with spreading disease
Shared processing – intermediate, limited due to high astringency
Co-marketing – intermediate, limited product could be marketed through common outlets

Integration potential – considered unsuitable

Does not appear to be economically sustainable by itself (due to limited appeal) and could have negative impact on fruit system as a source of fire blight.

History and background

European mountain ash is not related to the true ash tree, which belongs to the genus Fraxinus, rather it is a species of Sorbus that is native throughout northern Europe and in the mountains of southern Europe and southwest Asia. It has become widely naturalized in northern North America, primarily as a small landscape tree and wildlife food plant. This 20-40 foot tree likes full sun and is winter hardy to -40 degrees F (Zone 3). It prefers well-drained loams but will grow in most soils as long as they have adequate moisture and are not water-logged.

Technically a pome fruit, like apples and pears, European mountain ash fruit is often mistakenly referred to as berries due to their small size. In Britain, the fruit is made into a slightly bitter jelly and eaten with game. The fruit, which is high in tannin and pectin, can be used in jams and other preserves — on its own or with other fruit. A contributor to Pomona (winter 2005, Vol. XXXVIII No 4, page 75) from Norway said, “Here, the juice of mountain ash berries is used by gourmets to make a very delicious jelly.”

Raw European mountain ash, which is too astringent to be eaten, contains parasorbic acid, which is a known carcinogen (Pieters and Vlietinck, 1991). While some sources claim that parasorbic acid has antibiotic properties (North Dakota Tree Handbook), these properties have only been observed in structural analogs of parasorbic acid synthesized by molds (Ciegler et al., 1971). Heat treatment (cooking, heat drying, etc.) and to a lesser extent, freezing, may neutralize parasorbic acid. The seeds probably contain hydrogen cyanide, also toxic (Plants for a Future).

Observations at Carandale Farm

Carandale ordered a European mountain ash selection from Northwoods Nursery (One Green World) in 2003. ‘Rabina’ was said to be an unusual and unique form of mountain ash from Russia, selected for its good tasting fruit as described in the Northwoods catalog.

• The trees initially adapted well to the test site.
• They started producing fruit by the third year.
• The fruit is borne on clusters called cymes (similar to aronia).
• The tree form is very upright.
• Root suckering is significant.
• Contrary to the description in the Nortwoods catalog, the fruit is very astringent (high in tannins), making it unpalatable as a fresh fruit.
• The fruit is abundant and attractive as a wildlife food source.
• The trees started to decline and suffered dieback after year seven.

Discussion

If ‘Rabina’ is one of the better selections, European mountain ash does not pass the tests for hardiness, fruit quality, processing versatility and disease resistance. It has nothing to contribute to an integrated cropping system and may, in fact, be detrimental due to its susceptibility to fire blight, canker and borers that could be spread to other less susceptible species.

Carandale does not recommend that European mountain ash as an economically sustainable stand-alone fruit crop. It has no fresh fruit appeal, would be difficult to process economically into appealing value-added products and does not have any known unique nutraceutical properties. Carandale will be removing this species from the test plot.

References

Wikipedia entry on European Mountain Ash
North Dakota Tree Handbook: European mountain-ash
Plants for a Future: Sorbus acuparia

Pieters, LAC and Vlietinck, AJ. 1991. “Naturally Occurring Carcinogens in Plant Foodstuffs.” In Poisonous Plant Contamination of Edible Plants, Abdel-Fattah M. Rizk, ed. CRC Press, p.16

Ciegler, A, RW Detroy and EB Lillehoj. 1971. “Patulin, Penicillic Acid, and Other Carcinogenic Lactones.” In Microbial Toxins Vol. 6, ed. Ciegler, A, et al. Academic Press, Inc., New York and London, p. 425-426. <http://naldc.nal.usda.gov/download/31546/PDF>, accessed 6/28/13.