The Brian O Mulligan Sorbus Collection

Sorbus anglica September 2010
 

Sorbus aria 'Salicifolia' September 2010

Sorbus bristoliensis May 2010

Sorbus cashmiriana May 2010

Sorbus forrestii September 2010

Sorbus forrestii May 2010

Sorbus gonggashanica September 2010

The Brian O Mulligan Sorbus Collection can be found at the Washington Park Arboretum in Seattle.  This collection is the most complete in North America, containing 77 different taxa (species, forms, hybrids & cultivars) divided into sections for simple-leaved & compound-leaved forms.  The collection was named in honor of Brian O Mulligan, Director of the Washington Park Arboretum from 1947 to 1972.  His interest in Sorbus guided the renovation & redesign of the collection.  According to Mulligan, writing for the Spring 1990 edition of the Washington Park Arboretum Bulletin, the 1st plantings of Sorbus were made in 1949 & 1950.  As of 1990, when the collection was renovated, there were 50 taxa.  Most of those were raised from seeds received from many arboreta & botanical gardens, mainly in Europe.  27 new taxa have been added since 1990, including several important Chinese species. 

Sorbus is a genus of 100 to 200 species of trees & shrubs in the family Rosaceae.  Sorbus species are commonly known as whitebeam (simple-leaved forms) & mountain ash (compound-leaved forms).  Sorbus aucuparia (rowan) is the most common species of mountain ash found in the Seattle area.  Unfortunately, it has become a weed that has given the genus a bad reputation.  Among the 100+ species are many that make excellent garden trees.  The City of Seattle approves Sorbus aucuparia 'Michred' & Sorbus x hybrida as street trees.  The Sunset Western Garden Book calls Sorbus, 'good small garden trees.'  The Hillier Gardener's Guide to Trees & Shrubs says, 'Sorbus is one genus that provides ornamental features throughout the year & does so without needing much care.'

Among the most beautiful & often-used species are Sorbus aria, Sorbus cashmiriana, Sorbus commixta & Sorbus hupehensis.  I believe Sorbus scalaris has the most beautiful flowers.  In my own garden are Sorbus 'Birgitta', Sorbus forrestii & Sorbus gonggashanica.  I have raised seedlings taken from Sorbus hupehensis & Sorbus rehderiana in the Brian O Mulligan Sorbus Collection.  But of course, with so many other species nearby, those are likely to be hybrids.  A blog devoted solely to Sorbus is Rowans, Whitebeams and Service Trees written by Dr Patrick Roper.

List of plants & their number in the Brian O Mulligan Sorbus Collection
Sorbus alnifolia  2
Sorbus anglica  2
Sorbus americana  2
Sorbus amurensis  1
Sorbus aria  2
Sorbus aria f. longifolia  2
Sorbus aria 'Lutescens' 1
Sorbus aria 'Salicifolia' 1
Sorbus aucuparia 1
Sorbus aucuparia 'Cardinal Royal'  1
Sorbus austriaca  2
Sorbus 'Birgitta'  2
Sorbus bristoliensis  1
Sorbus caloneura  2
Sorbus cashmiriana  3
Sorbus commixta  12
Sorbus commixta 'Embley'  1
Sorbus dacica  3
Sorbus decora  1
Sorbus devoniensis  3
Sorbus discolor 'Apricot Queen'  1
Sorbus domestica  3
Sorbus esserteauiana  1
Sorbus filipes  5
Sorbus folgneri x Sorbus alnifolia  1
Sorbus forrestii  3
Sorbus gracilis  1
Sorbus gonggashanica  1
Sorbus helenae 1
Sorbus himalaica  1
Sorbus x hostii  2
Sorbus hupehensis  2
Sorbus x hybrida  2
Sorbus x intermedia  1
Sorbus japonica  1
Sorbus javorkae  1
Sorbus koehneana  3
Sorbus kusnetzovii  1
Sorbus lanata  2
Sorbus latifolia  2
Sorbus megalocarpa  1
Sorbus x meinichii  1
Sorbus meliosmifolia  1
Sorbus microphylla  3
Sorbus minima  2
Sorbus mougeotii  1
Sorbus pallescens  3
Sorbus prattii  1
Sorbus pogonopetala  1
Sorbus porrigentiformis  1
Sorbus poteriifolia  1
Sorbus pygmaea  1
Sorbus randaiensis  1
Sorbus redliana  1
Sorbus reducta  1
Sorbus rehderiana     1
Sorbus rehderiana form     1
Sorbus rehderiana 'Joseph Rock'  1
Sorbus aff. rehderiana  3
Sorbus sargentiana  4
Sorbus scalaris  3
Sorbus scalaris hybrid  1
Sorbus scopulina var. cascadensis  5
Sorbus x splendida  1
Sorbus subcuneata  1
Sorbus subsimilis  1
Sorbus tamamschjanae  1
Sorbus thibetica  1
Sorbus x thuringiaca 'Fastigiata'  1
Sorbus torminalis  1
Sorbus turkestanica  1
Sorbus umbellata  1
Sorbus umbellata var. cretica  3
Sorbus ursina  2
Sorbus vestita  1
Sorbus 'Wilfrid Fox'  3
Sorbus zahlbruckneri