May Color Appears at the Washington Park Arboretum

May 15th, 2015 by UWBG Horticulturist
Selected cuttings from the Washington Park Arboretum (May 11-24, 2015)

Selected cuttings from the Washington Park Arboretum (May 11-24, 2015)

1)  Cytisus x praecox ’Luteus’           Warminster Broom

  • This broom is a hybrid of C. multiflorus and C. purgans and is located on Arboretum Drive in the Legume Collection.
  • Many of the brooms are blooming now or soon to bloom, including the pineapple broom, Argyrocytisus battandieri, whose fragrance earned it its common name.

2)  Erica arborea var. alpina           Tree Heath

  • While non-alpine tree heath can reach heights in excess of 20 feet, the alpine variety is the “short” one, reaching only 10 to 15 feet.
  • Alpine tree heath has white flowers versus light-gray, and the scent is reminiscent of honey.

3)  Hydrangea luteovenosa           Sweet Hydrangea

  • In full bloom now, this semi-trailing Hydrangea is located on the Ridgetop Trail in Rhododendron Glen.
  • Though widely distributed in western Japan, this species of Hydrangea is critically endangered in Korea.

4)  Rhododendron ‘Snow Lady’ x Rhododendron degronianum ssp yakushimanum

  • Hybrids are often created to blend two or more outstanding traits from two separate taxa into one single plant, e.g. flower color and leaf indumentum.
  • There are several areas in the Washington Park Arboretum, including Azalea Way, Loderi Valley, Rhododendron Glen and the Puget Sound Rhododendron Hybridizers bed, showcasing many hundreds of hybrids of Rhododendron.

5)  Syringa reflexa           Nodding Lilac

  • The buds of Syringa reflexa start out a rosy–red before opening to pink and eventually fading to almost white.
  • The specific epithet “reflexa” refers to the nodding habit of the flower heads.
  • Lilacs are located throughout the Washington Park Arboretum, though many are found just south of the Woodland Garden along Azalea Way.

The Boys and Girls and Their Boats

May 1st, 2015 by UWBG Horticulturist
Selected cuttings from the Washington Park Arboretum (April 27 - May 10, 2015)

Selected cuttings from the Washington Park Arboretum (April 27 – May 10, 2015)

Opening Day crew races through the Montlake Cut, and the 1936 USA Olympic gold in rowing may never have happened without these following trees:

1)  Thuja plicata        Western Red Cedar

  • UW’s world-renowned boat maker, George Pocock followed the lead of Native Americans and used this Pacific Northwest giant for the hulls of his Pocock Classics.
  • The skin is made from a single plank of 3/32″ thick cedar and offers a combination of stiffness and springiness that eliminates the need for the extra weight of a hull.

2)  Pinus lambertiana        Sugar Pine

  • Keels of Pocock’s boats were made from this soft, even-grained Oregon native.
  • Sugar pine has very low shrinkage when it dries, so hull warping and cracking was kept to a minimum with this choice wood.

3)  Xanthocyparis nootkatensis        Alaska Yellow Cedar

  • Cheeks (two lowest timbers at the head rails) and washboards (thin planks fastened to the side to keep out water) were made from this honey-colored wood.
  • Pocock was especially fond of the way Xanthocyparis aged with Thuja plicata.

4)  Picea sitchensis       Sitka Spruce

  • Hand-carved seats and gunnels (uppermost plank in a hull) were made from these giants from Vancouver, BC.

5)  Picea engelmannii        Engelman Spruce

  • Oars used in rowing competitions are made from Engelman Spruce.
  • The oar consists of three bonded pieces made from one single plank of Engelman spruce split to make mirror-imaged sides, and another piece is cut for the center.

Resources:  http://www.pocockclassic.org, http://shipwrightjournal.blogspot.com

April Color Appears at the Washington Park Arboretum

April 19th, 2015 by UWBG Horticulturist
Selected cuttings from the Washington Park Arboretum (April 13 - 26, 2015)

Selected cuttings from the Washington Park Arboretum (April 13 – 26, 2015)

1)  Acer cissifolium        Vine-leaf Maple

  • A three-leaf maple native to Japan.
  • The extraordinary racemes of tiny flowers give the tree a cloud-like appearance.
  • Located in the Asiatic Maple Collection.

2)  Acer rubrum        Red Maple

  • This popular street tree is native to eastern North America.
  • On this sample the petals have fallen, leaving the elongating peduncles and their tiny, immature samaras.
  • Located in grid 3-5E on Arboretum Drive.

3)  Cornus florida        Flowering Dogwood

  • Named for its showy bracts.
  • Native to the eastern United States.
  • These cuttings are from ‘Royal Red’ near the south end of Azalea Way and from an unlabeled white cultivar near the north end.

4)  Cornus nuttallii        Pacific Dogwood

  • A west coast native named for Thomas Nuttall– a British botanist and explorer.
  • Natural seedlings are scattered throughout the Arboretum.
  • This is the provincial “flower” and floral emblem of British Columbia.

5)  Cornus nuttallii x florida    ‘Eddie’s White Wonder’

  • So named because it was one of a few survivors of a flood at Henry Eddie’s nursery near Vancouver, B.C.
  • It is a hybrid of Cornus nuttallii and C. florida.
  • Several specimens are growing along Azalea Way.

Core Collection Highlight: Viburnum

April 5th, 2015 by UWBG Horticulturist
Selected cuttings from the Viburnum Collection at the Washington Park Arboretum (3/30/15-4/13/15)

Selected cuttings from the Viburnum Collection at the Washington Park Arboretum (3/30/15 – 4/13/15)

Our Viburnum Collection is recognized as one of the top three national collections. Our taxonomic display currently is home to over 100 different kinds and 330 living specimens.
[Description references: “Viburnums — Shrubs for Every Season” by Michael Dirr.]
Here are a few samples of this diverse and ornamental shrub.

1)  Viburnum carlesii var. bitchiuense        Bitchu Viburnum

  • Wonderfully fragrant flowers in early spring.
  • Closely allied to V. carlesii.  Botanists still debate whether to “split” or “lump”.
  • Located across from the Graham Visitor Center in full flower. Grid: 40-3E

2)  Viburnum macrocephalum       Chinese Snowball Viburnum

  • 6’-10’ rounded shrub.
  • Known for 3″ – 8″ wide, hemispherical cymes, hence the name “Snowball”.
  • Located along maintenance facility mixed-shrub border fence. Grid: 43-5E

3)  Viburnum propinquum

  • Large evergreen shrub with glossy three-veined leaves.
  • Known to be tender in cold Pacific Northwest winters.
  • Located in the Rhododendron Glen parking lot landscape. Grid: 12-8E

4)  Viburnum x rhytidophylloides ‘Alleghany’        Lantanaphyllum Viburnum

  • National Arboretum introduction in 1958.
  • Handsome dense evergreen shrub with abundant inflorescences.
  • Located in Viburnum Collection. Grid: 25-5W

5)  Viburnum utile        Service Viburnum

  • Rare in commerce, but important evergreen species for breeding.
  • Dirr doesn’t think it has much ornamental value. I (David Zuckerman) disagree.
  • Located in Viburnum Collection. Grid: 26-4W

March Color Appears at the Washington Park Arboretum, Part II

March 23rd, 2015 by UWBG Arborist, Chris Watson
Selected cuttings from the Washington Park Arboretum (March 16-30, 3015)

Selected cuttings from the Washington Park Arboretum (March 16 – 30, 3015)

1)  Acer tegmentosum  ‘Joe Witt’        Stripebark Maple

  • A small- to medium-size tree with distinct striped patterns along the bark and branches
  • Named for a former Washington Park Arboretum curator
  • Located in the Joe Witt Winter Garden

2)  Berberis x media  ‘Arthur Menzies’        Hybrid Mahonia

  • Multi-stemmed shrub with prominent winter flowers
  • Loved by hummingbirds as a source of winter nectar
  • Located in the Joe Witt Winter Garden

3)  Ceanothus  ‘Puget Blue’        California Lilac

  • A fast growing, medium-sized shrub
  • Known for small dark, evergreen leaves and purplish-blue late spring flower
  • Located along the fence in the Graham Visitors Center’s parking lot

4)  Magnolia x kewensis  ‘Wada’s Memory’        Hybrid Magnolia

  • Selected from a group of seedlings from nurseryman, Koichiro Wada
  • Known for large and abundant spring flowers
  • Two specimens flank Arboretum Drive near the Hydrangea Collection

5)  Nothofagus antarctica  ‘Puget Pillar’        Southern Beech

  • A medium-sized deciduous tree native to Argentina and Chile
  • Known for a somewhat fastigiate growth habit
  • Located along the shore near Duck Bay

Early Spring Has Begun!

March 6th, 2015 by UWBG Horticulturist
Selected cuttings from the Washington Park Arboretum (March 2 - 16, 2015)

Selected cuttings from the Washington Park Arboretum (March 2 – 16, 2015)

1)  Acer triflorum        Three Flower Maple

  • A small, slow-growing deciduous tree 20’ to 45’ where it is native in Manchuria and Korea.  An excellent landscape tree boasting light grey vertically-furrowed bark and vivid red and orange fall color.  The name refers to its flowers, which are borne in clusters of three.
  • Discovered by noted plant explorer, Ernest H. Wilson in 1917.
  • Located in the Asiatic Maples Collection.  Grid: 26-B

2)  Corylopsis sinensis var. calverescens        Winter Hazel

  • A medium-sized deciduous, broadly vase-shaped shrub in the Witch Hazel family.
  • Bean describes it as flowering in April.
  • Located in the Witt Winter Garden.  Grid: 34-1E

3)  Magnolia x loebneri‘Ballerina’        Magnolia

  • This small deciduous tree is a hybrid between M. x loebneri ‘Spring Snow’ and M. stellata ‘Water Lilly’.
  • The specific epithet honors Max Loebner, a German horticulturist, who made the first cross of this hybrid in the early 1900s.
  • Located on the west side of Arboretum Drive in the Magnolias Collection.  Grid: 28-4E

4)  Rhododendron thomsonii ssp. thomsonii        ‘Glory of Penjerrick’

  • A large evergreen shrub with a rounded crown noted for very early bloom time.
  • An early hybrid used as parent for many subsequent Rhododendron hybrids.
  • Located west of Azalea Way, north of the path to the Wilcox foot bridge.

5)  Sorbus caloneura        Whitebeam

  • This small upright deciduous tree is native to southeastern China and Tibet.
  • The leaves are heavily pleated, giving them the appearance of beech leaves.
  • Fruit are extremely hard and persist well into winter.
  • Located at the south end of the Sorbus Collection.  Grid: 20-4E

February Color Appears at the Washington Park Arboretum

February 22nd, 2015 by UWBG Horticulturist
Selected cuttings from the Washington Park Arboretum (February 17 - March 1, 2015)

Selected cuttings from the Washington Park Arboretum (February 17 – March 1, 2015)

1)  Camellia japonica      ‘Nina Avery’

  • Due to this year’s mild winter thus far, many plants here have begun flowering much earlier than normal, and Camellias are certainly no exception. Many specimens can be seen in bloom along Arboretum Drive near Rhododendron Glen.

2)  Camellia x williamsii      ‘Mary Christian’

  • Soon after C. saluenensis began to flower it was crossed with C. japonica, notably by J. C. Williams at Caerhays. One of the first plants raised there was named ‘Mary Christian’.
  • Trumpet-shaped, single, carmine-pink flowers are currently on display.

3)  Larix kaempferi      Japanese Larch

  • The needle-shaped leaves of L. kaempferi are just beginning to emerge.
  • Native to Japan and able to reach 80-100 feet in height, this species was introduced by John Gould Veitch in 1861.
  • A member of the family Pinaceae, this specimen is located in the Pinetum near the Stone Bridge.

4)  Magnolia      ‘Royal Crown’

  • This is a popular clone with dark red-to-violet flowers, white on the inside. It was first hybridized by D. Todd Gresham of Santa Cruz, California, who sometimes referred to plants of his cross as the “svelte brunettes” because of the dark color and sleek form of the flowers.
  • Located along Arboretum Drive within the Magnolias.

5)  Symphoricarpos orbiculatus      Coralberry

  • A dense, bushy shrub with ornamental fruit currently on display.
  • Native to the United States.
  • Specimen located within the Viburnums.

February Color Appears at the Washington Park Arboretum

February 4th, 2015 by UWBG Horticulturist
Selected cuttings from the Washington Park Arboretum (February 2 - 15, 2015)

Selected cuttings from the Washington Park Arboretum (February 2 – 15, 2015)

Donald Culross Peattie in the Washington Park Arboretum

Staff horticulturist, Ryan Garrison recently listened to an audio version of Donald Culross Peattie’s book, “A Natural History of North American Trees.” He very much enjoyed its mix of science and literary art, and would like to share a few gems about trees in the collection with you.

1)  Carya ovata – Shellbark or Scalybark Hickory
“To everyone with a feeling for things American, and for American history, the Shagbark seems like a symbol of the pioneer age, with its hard sinewy limbs and rude, shaggy coat, like the pioneer himself in fringed deerskin hunting shirt. And the roaring heat of its fires, the tang of its nuts – that wild manna that every autumn it once cast lavishly before the feet – stand for the days of forest abundance.” 1

2)  Pseudotsuga menziesii – Douglastree; Douglas, yellow, or Red Spruce; Oregon Pine
“In the literature of forestry it has wavered between Douglas Fir and Douglas Spruce, though it is no Spruce and no true Fir, as botanist see matters. Some years ago the Forest Service officially settled on “Douglas Fir” and if this impaction seems to you to clear up matters, you may use it with the blessings of the Government Printing Office. The least misleading of proposed names is Douglastree, since it leans on no analogies and still does honor to that noble pioneer among explorer-botanists of the Northwest, David Douglas.” 1

3)  Sequoia sempervirens – California Redwood, Coastal Sequoia, Sempervirens, Palo Colorado
“Your footfalls make no sound on the needles and moss that have lain there for centuries. Your body casts no shadow in that green, lake like diffused light. The goose honking of a car, the calling of a child, fade into the immensity of silence. Time, the common tick-tock of it, ceases here, and you become aware of time in another measure – out of an awesome past. For this forest has stood here since the Ice Age, and here, together with this transfixed past, is the future too, for these immense lives will outlast yours by a thousand years or so.” 1

4)  Sequoiadendron giganteum – California Bigtree; Sierra Redwood; Mammoth-tree
“The summers are exceedingly dry; if rain does fall it is apt to come with violent thunderstorms and lightning bolts that have been seen to rive a gigantic Sequoia from the crown to its roots. Those who know the species best maintain that it never dies of disease or senility. If it survives the predators of its infancy and the hazard of fire in youth, then only a bolt from heaven can end its centuries of life. Perhaps, if this majestic tree had a will, it would prefer to go this way, by an act of God.” 1


1 Peattie, Donald Culross, and Paul Landacre. A Natural History of North American Trees. Boston: Houghton Mifflin, 2007. Print.

January Color Appears at the Washington Park Arboretum (Part II)

January 25th, 2015 by UWBG Horticulturist

Witt Winter Garden

Selected cuttings from the Washington Park Arboretum (January 19-31, 2015)

Selected cuttings from the Washington Park Arboretum (January 19-31, 2015)

1)  Cornus sanguinea ‘Midwinter Fire’         Bloodtwig Dogwood

  • Young stems of this cultivar are orange-yellow with the sunny side turning carmine red.
  • Stem color of species is gray to purple, while the color of C.s. ‘Midwinter Fire’ is yellow-green in summer changing to winter colors rapidly at leaf drop in fall.

2)  Hamamelis x intermedia ‘Pallida’             Witch Hazel

  • This hybrid of H. japonica and H. mollis was selected for its pale sulfur-yellow flowers which tend to glow in the low light levels of morning and evening.
  • Cultivars of witch hazel can have flower colors from pale yellow to deep red, some being quite fragrant while others are much less so.

3)  Lonicera standishii                   Honeysuckle

  • This semi-evergreen shrub bears fragrant flowers from early winter to early spring.
  • Lonicera standishii is native to China.

4)  Ruscus aculeatus                    Butcher’s Broom

  • Lacking true leaves, what you are seeing are called “cladophylls” which are simply flattened stems.
  • The flowers of this plant are dioecious, only 2 mm across and are located in the center of the cladophylls.
  • Butcher’s Broom is native to Europe, Turkey, North Africa and the Azores.

5)  Viburnum tinus ‘Pink Prelude’                Laurustinus

  • This species has been cultivated in England since the 16th century.
  • V.t. ‘Pink Prelude’ has white flowers that age to pink.
  • The flowers of laurustinus are followed by small, but showy metallic-blue fruit.

January Color Appears at the Washington Park Arboretum

January 11th, 2015 by Kathleen DeMaria, Arboretum Gardener
Selected cuttings from the Washington Park Arboretum        (January 5 - 18, 2015)

Selected cuttings from the Washington Park Arboretum (January 5 – 18, 2015)


“Piercing, sucking and galling!”

1)  Mites (on Sasa Bamboo and Skimmia)

  • Stippling and yellowing of leaves are often indicative of the presence of mites.
  • Feed by piercing underside of leaves and sucking chlorophyll out decreasing photosynthesis, reducing plant vigor and compromising the appearance.
  • Mites are not insects; they are arachnids.

2)  Galls (on Willow and Rose)

  • Abnormal plant growths caused by various organisms (insects, mites, fungi, etc.)
  • Galls are formed by increased production of normal plant hormones as response to feeding, egg-laying or disease infiltration and are often not harmful to the plant.
  • Galls can be on leaves, stems, twigs, buds, flowers and roots

3)  Blights (on Hazelnut and Cherry)

  • Refers to a symptom affecting plants in response to infection by a pathogen.
  • Blights come on rapidly and can cause complete chlorosis and browning of plant tissues such as leaves, branches and twigs; plant death is not uncommon.
  • Aided by cool, moist conditions and limited air flow to plants…perfect for the Pacific Northwest!

4)  Phylloxera (on Oak)

  • Microscopic, yellow sucking aphid relatives that feed on leaves and buds.
  • Yellowish spots on leaves in spring turn to brown by summer and defoliate.
  • Repeated defoliation abates photosynthesis and can lead to plant death.

5)  Armillaria root rots (shown on Bigleaf Maple, but many trees are susceptible)

  • Fungus cause stunted leaves, chlorotic needles, dieback of twigs and branches and eventually death.
  • Identified by white mats of fungal mycelium between the inner bark and wood and honey-brown mushrooms growing on or around the base of the tree.
  • A big threat to the lumber industry as the wood is unsalvageable.