Permaculture Plants: Sorbus Species

Scientific Name: Sorbus species (there is a push to divide the Sorbus genus)
Family: Rosaceae (the Rose family)

Common Species:

• Whitebeam (Sorbus aria): good wood; up to 0.625 inch (16 mm) oval, red fruit; mealy but sweet
• Korean Mountain Ash (Sorbus alnifolia): good wood; up to 0.5 inch (13 mm) pink to purple fruit, mealy with a mild to spicy flavor
• American Mountain Ash (Sorbus americana)
• Rowan or European Mountain Ash (Sorbus aucuparia): good wood; bitter but edible fruit
• Showy or Northern Mountain Ash (Sorbus decora)
• Devon Sorb Apple (Sorbus devoniensis):0.6 inch (15 mm) fruits; almond flavor, mealy texture
• Service Tree or Sorb Tree (Sorbus domestica): good wood; 1.0-1.6 inch (2.5-4 cm) fruits shaped like small apples or pears depending on the variety, astringent until fully ripe, but then juicy, aromatic, and with a good flavor (tropical or pear-like). Cooking will remove the astringency of slightly under-ripe fruit.
• Tibetan Whitebeam (Sorbus thibetica): 0.75 inch (19 mm) fruits, almond flavor, mealy texture
• Wild Service Tree (Sorbus torminalis): good wood; 0.3-0.6 inch (10-15 mm) oval fruit with good flavor similar to a date (pictured at top)
• Yu’s Mountain Ash (Sorbus yuana): 0.75 inch (19 mm) pink to purple fruit with a spicy flavor

Description:
It has been only recently (in the grand scheme of time) that the fruits from these trees have been replaced by the more “common” fruits in grocery stores, like apples and oranges; however, the Sorbus fruits were once very popular in Europe and have many uses from fresh eating to preserves to flavorings for beers and wines.  The wood of European and some Asian species are very high quality, very hard woods. The trees can be coppiced, can be a windbreak, can attract wildlife, and are ornamental as well. It is time we reconsider these almost forgotten trees in our Forest Gardens.

History:
Native to temperate forests of the Northern Hemisphere, the Sorbus genus contains about 200 species. They have long been used for their fruits and their wood. In more recent times, many of the species have been used as ornamentals, and a number have been improved to yield more and better-tasting fruits.

Trivia:

• The Wild Service Tree’s fruits were fermented by the Romans to make a drink named cerevisia, which is the origin of the Spanish word, cerveza, or beer!
• The Wild Service Tree’s species name, torminalis, is Latin meaning “good for colic”, a reference to its historical medicinal use
• Many of the Sorbus species can pollinate each other and produce hybrids. Many of these hybrids are considered apomictic, that is they are self-fertile without the need of pollination. These plants are able to repoduce genetically identical copies of itself, i.e. cloning, through seed!

Primary Uses:

• Edible Fruit:
  • Raw – some improved varieties have good flavored fruit when raw. However, many of the fruits can be bletted – this is where the fruit is placed in a coold, dry place and allowed to significantly over-ripen, but not rot. The soft fruit will often have a sweet, tropical fruit flavor. Some trees will keep the fruit, and the bletting will start on the tree. Most fruits on the tree will turn sweeter after a frost.
  • Cooked – used in sauces and savory meals
  • Baked – used in pastries, tarts, pies, etc.
  • Preserved – used in Jams, Jellies, Preserves, etc.
  • Fruit Leather
  • Dried – miltiple references for drying these fruits with flavors ranging from prunes to dates
  • Primary or Secondary flavoring for Beers, Wines, Liquors, Cordials, etc. The Wild Service Tree was a traditional addition to beers before the spread of hops. Cider was, and still is today, flavored with fruits from the Service Trees.
  • Flour – the fruits from the Rowan (S. aucuparia), Whitebeam (S. aria), the American Mountain Ash (S. americana), and maybe other species as well, can be dried and ground into a flour and mixed with other cereal flours.
• Tea Plant – Rowan (S. aucuparia) flowers and leaves have been used a tea substitute

Secondary Uses:

• General insect (especially bees) nectar and pollen plant
• Wildlife Food – many animals will eat the fruit through Autumn and Winter
• Ornamental Plant- showy Spring flowers, bright Autumn reds and golds, bright fruit remaining after leaf-fall
• Windbreak Species
• Maritime Species – S. aucuparia, S. aria can tolerate salty conditions
• Pollution-Tolerant Species – these trees can live in areas with high air pollution
• Coppice Species – coppiced through Europe without a doubt, but I can find no time references instructing how long it takes to regrow before coppicing can occur again
• Wood Species – Rowan is very hard and used for mallet heads, hoops for barrels, cogs, furniture, etc.; Service Tree used for furniture, wine presses; Whitebeam is hard, heavy, and good for beams (hence the name!); Wild Service Tree used for turning, carving, crafts, etc.
• Firewood Species – vary aromatic
• Charcoal

Yield: Once producing, these trees can produce about 30 pounds (13.5 kg) per tree.
Harvesting: Early to mid Autumn. Pick when the fruits are fully ripe if possible and the fruit begins to soften. Most fruits will ripen indoors in need be, but wait until the fruit softens before eating or processing.
Storage: Used fresh. Will store for a few weeks in a cool location.

USDA Hardiness Zone:

• Whitebeam (Sorbus aria): Zone 5-9
• Korean Mountain Ash (Sorbus alnifolia): Zone 4-8
• American Mountain Ash (Sorbus americana): Zone 2-6
• Rowan (Sorbus aucuparia): Zone 3-7
• Showy Mountain Ash (Sorbus decora): Zone 2-6
• Devon Sorb Apple (Sorbus devoniensis): Zone 6
• Serice Tree or Sorb Tree (Sorbus domestica): Zone 4-10
• Tibetan Whitebeam (Sorbus thibetica): Zone 6
• Wild Service Tree (Sorbus torminalis): Zone 6
• Yu’s Mountain Ash (Sorbus yuana): Zone 3-8

AHS Heat Zone:

• Whitebeam (Sorbus aria): Zone 8-6
• Korean Mountain Ash (Sorbus alnifolia): Zone 8-3 or 10-1 depending on the source
• American Mountain Ash (Sorbus americana): Zone 6-1
• Rowan (Sorbus aucuparia): Zone 7-1
• Showy Mountain Ash (Sorbus decora): Zone 6-1
• Serice Tree or Sorb Tree (Sorbus domestica): Zone 8-6
• Yu’s Mountain Ash (Sorbus yuana): Zone 8-3 or 10-1 depending on the source

Chill Requirement: Likely considering where this plant originates, but no reliable information is available.

Plant Type: Small to Medium Tree
Leaf Type: Deciduous
Forest Garden Use: Canopy Layer, Sub-Canopy Layer
Cultivars/Varieties: There are a number of species and varieties available

Pollination: Most of the wild types require cross-pollination from another tree; some of the improved varieties (especially with the Service Tree) are Self-fertile, but will likely set more fruit with cross-pollination. Pollinated by insects.
Flowering: Late Spring to Summer (May-June), not frost sensitive

Life Span:

• Years to Begin Fruiting: 3-5 years, but 15 years for the Rowan (S. aucuparia)
• Years to Maximum Fruiting: No good information available
• Years of Useful Life: Many species are considered “short lived” with no specific dates, but the Rowan (Sorbus aucuparia) and the Whitebeam (Sorbus aria) are reported to live for well over 100 years of age. The Service Tree (Sorbus domestica) has been reported to live to 400 years. Coppicing greatly extends the life of a tree as well.

Size:

• Whitebeam (Sorbus aria): 40 feet (12 meters) tall and 25 feet (8 meters) wide
• Korean Mountain Ash (Sorbus alnifolia): 50 feet (15 meters) tall and 25 feet (8 meters) wide
• American Mountain Ash (Sorbus americana): 10-30 feet (3-9 meters) tall and wide
• Rowan (Sorbus aucuparia): 20-40 feet (6-12 meters) tall and 15-35 feet (4.5-11 meters) wide
• Showy Mountain Ash (Sorbus decora): 20-35 feet (6-11 meters) tall and wide
• Devon Sorb Apple (Sorbus devoniensis): 20 feet (6 meters) tall and 13 feet (4 meters) wide
• Serice Tree or Sorb Tree (Sorbus domestica): 30-35 feet (9-11 meters) tall and 20-30 feet (6-9 meters) wide; can get to 60 feet (18 meters) tall
• Tibetan Whitebeam (Sorbus thibetica): 33-50 feet (10-15 meters) tall and wide
• Wild Service Tree (Sorbus torminalis): 50-65 feet (15-20 meters) tall
• Yu’s Mountain Ash (Sorbus yuana): 20-40 feet (6-12 meters) tall

Roots: It appears that most of the European species have deep taproots with shallow lateral roots. Little else can be found about the other species other than the Showy Mountain Ash (S. docora) from North America, and it has fibrous roots.
Growth Rate: Medium

Light: Prefers full sun
Shade: Tolerates light shade, but fruits less
Moisture: Prefers medium moisture soils (S. decora can tolerate more wet soils).
pH: 5.1-7.0 (prefers mild acidic to neutral soils, but can tolerate a pretty wide range of soils).

Special Considerations for Growing:

• These are not fussy trees.
• Susceptible to the bacterial disease, Fire Blight. Would need to prune to treat the infected trees (cut 6 inches (15 mm) below infection).

Propagation:
Seed, requires 3-4 months of cold stratification. Improved varieties are grafted.

Maintenance:
Minimal once established.

Concerns:
Like many species in the Rose family, the leaves and seeds contain a precursor to cyanide which could be life threatening if consumed in large amounts.

 

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Photo References:

• http://upload.wikimedia.org/wikipedia/commons/c/c8/Sorbus_aucuparia_kpjas_19082005_4.jpg
• http://drzewaikrzewyozdobne.home.pl/boryslawice/attachments/Image/drzewa_li__ciaste/Sorbus_aucuparia2.jpg
• http://www.erbe.altervista.org/images/sorbus_aucuparia_B.jpg
• http://davisla.files.wordpress.com/2011/04/sorbus-aria2.jpg
• http://www.pflanzen-bilder-kaufen.de/wp-content/uploads/Speierling-Baum-Frucht-rot-gelb_Sorbus-domestica01.jpg
• http://upload.wikimedia.org/wikipedia/commons/3/3f/Sorbus_domestica.JPG
• http://www.pariscotejardin.fr/wp-content/09092011-P1360512.jpg
• http://delta-intkey.com/angio/images/ebo04811.jpg
• http://delta-intkey.com/angio/images/ebo04851.jpg
• http://upload.wikimedia.org/wikipedia/commons/e/e3/Sorbus_torminalis_Weinsberg_20070929_5.jpg
• http://upload.wikimedia.org/wikipedia/commons/0/05/Sorbus_alnifolia_’Submollis’_JPG1Ta.jpg
• http://farm3.staticflickr.com/2801/4471786077_a5362e8bfb_o.jpg