Mulberry

(Morus ssp)

Dormant Northrop
Dormant ‘Northrop’

Cultivars tested

‘Illinois Everbearing’, ‘Northrop’

Description and site preference

Type and size – trees up to 80 feet unpruned
Hardiness zone – 4-9 (extremely variable by cultivar)
Exposure – full sun
Soil – prefers deep loam
Drainage – well-drained

Economic factors

Years to harvest – 3-4 with transplants
Maintenance – mostly pruning for manageable harvest
Life of planting – 50+ years
Machine harvest potential – by tree shaking
Suitable markets – local, fresh, frozen, dried and wine

Dormant Illinois Everbearing
Dormant ‘Illinois Everbearing’

Notable features

Nutritional highlights – most are high in anthocyanins (potent antioxidants)
Adaptability – varies by cultivar
Pest issues – minimal
Invasive potential – can be invasive, but already naturalized
Environmental benefits – produces large amounts of pollen to support pollen collecting insects and bees

Integration characteristics

Shared management – minimal, specialized needs
Equipment sharing – pruning only
Shared processing – intermediate
Co-marketing – low, best for local markets

Integration potential – challenging

Mulberry could be part of an integrated system or grown in separate blocks. Combining tree fruits and hedge-grown fruits in an integrated system is ecologically beneficial but will require special design features to maintain good airflow and harvest convenience and reduce shading issues.

History and background

The Morus genus has 10-16 species of deciduous trees commonly known as mulberries, native to many temperate regions of the world. Three species are grown for their fruit. The red or American mulberry (Morus rubra L.) is native to the eastern U.S. The white mulberry (Morus alba L.) is native to eastern and central China. It was introduced to America for silkworm culture in early colonial times and has become naturalized. The black mulberry (Morus nigra L.) is native to western Asia.

Named for the color of its buds, the white mulberry is the most cold-hardy of the three species, with some cultivars unfazed at -25 degrees F. This naturalized species has hybridized with the native red mulberry, which is less winter hardy but can tolerate sub-zero temperatures. The black mulberry, which is a small tree that lives longer, is said to have the best quality fruit, is the least winter hardy and will not tolerate temperatures below zero (Zone 7). Cultivars for the northern growing areas (Zones 4-6) are either white or crosses between white and red. A more in-depth discussion can be found in Uncommon Fruits for Every Garden by Lee Reich.

Observations at Carandale Farm

Over 10 years, three mulberry cultivars have been observed in the Carandale test plot. In 2003, two plants of a white fruiting cultivar (M.alba) were ordered from Raintree Nursery and two plants of Illinosis everbearing (M. alba x rubra) were ordered from One Green World .

  • All four trees survived transplanting and grew well.
  • In August, deer pruned back the season’s new growth (before the permanent deer fence was installed). No damage was observed elsewhere in the test plot, so the mulberry must have been a delicacy.
  • The trees responded with a flush of new growth that apparently could not acclimate before winter — all four trees winter-killed. One of the white variety did re-sprout from the root, but never bore fruit, probably because it was grafted on a male root stock. (Mulberry can be either monoecious or dioecious.)
  • In 2006, five replacement plants of ‘Illinois Everbearing’ were ordered from Northwoods Nursery (see One Green World) and planted at two locations.
  • The plants grew but were never vigorous. Adaptation was especially poor at one location. One died, so growers removed the remaining two plants at that location and replaced them with another cultivar, ‘Northrop’, purchased from St. Lawrence Nurseries in 2008.
  • Northrop was described as a very hardy (M. alba) cultivar from Potsdam, New York. It has adapted well and started fruiting in 2011. The fruit is smaller than ‘Illinois Everbearing’, more like the naturalized species that grow in fence lines, but fruit quality is good. It ripens uniformly and is easily removed from the tree. Carandale suspects that it is a naturalized seedling from that region.
  • The remaining ‘Illinois Everbearing’ trees have been producing some fruit. Fruit is large and attractive, but growers have not been impressed with the flavor and its large, firm and tasteless core. Fruit clings to the tree, requiring multiple harvests that would reduce suitability for commercial production.

Discussion

Mulberry is like blackberry harvested from a tree, but sweeter, without thorns and with a little less flavor. The naturalized white mulberry is adapted to cooler regions of the temperate zone (at least to Zone 4). The fruit may lack the sweet-tart blend that gives black mulberry superior flavor, but it is an acceptable alternative.

Mulberry is also a dependable fruiting plant. It is one of the last trees to begin growth in the spring, so flowers are hardly ever damaged by late-spring frosts. Adapted clones are tolerant of poor soils, drought and urban pollution, but adaptability does seem to vary. ‘Northrop’, which is probably a pure strain of white (M.alba), is vigorous in the test plot. ‘Illinois Everbearing’, a cross between white and red, is struggling.

Mulberry could be harvested mechanically with tree shaking systems similar to those used to harvest tart cherries for processing. White mulberries dislodge easily when shaken (‘Illinois Everbearing’ does not). Riper berries would make a good juice, especially blended with a more tart fruit. Less ripe berries can be used for pies, tarts and other baked items. Mulberry is also becoming popular for winemaking.

References

Wikipedia entry on Mulberry
Uncommon Fruits for Every Garden, by Lee Reich
California Rare Fruit Grower, Inc., information on Mulberry

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