June 15th, 2014 by UWBG Horticulturist
1) Hydrangea macrophylla ‘Madame Emile Mouillere’
- A blizzard white beauty all summer, long considered the best white mop head.
- A charming companion to evergreen shrubs.
- A beautiful 70-year old specimen graces the Hydrangea Collection along the Arboretum Drive.
2) Leucothoe davisiae (Sierra Laurel)
- Native to the mountains of northern California and southern Oregon.
- One of 4,000 species in the Ericaceae family.
- A 20-year old specimen can be found in the Rhododendron Glen.
3) Rosa moschata ‘Plena’ (Double Musk Rose)
- Cultivated in European and American gardens for centuries.
- Grown for its strong, clove musk fragrance and abundant alabaster white flowers.
- A 65-year old specimen is flourishing by the entrance to the horticulture headquarters.
4) Stewartia pseudocamellia var. koreana (Korean Stewartia)
- Native to Japan and Korea, this tree has garnered the Royal Horticulture Society’s Award of Garden Merit.
- The flowers are white with orange anthers, shaped like those of the related camellia.
- A graceful 64-year old specimen is growing beautifully at the south end of Arboretum Drive.
5) Philadelphus lewisii (Lewis’ Mock Orange)
May 29th, 2014 by UWBG Horticulturist
Selected cuttings from the Washington Park Arboretum (May 27 – June 8, 2014)
1) Crataegus crus-galli Cockspur Hawthorn
- Native to eastern North America, this small deciduous tree has a pleasant habit and is now showing off its small white flowers, but don’t get too close! The rigid thorns can be up to three inches long.
- Hawthorns are classified within the plant family Rosaceae, and are allied to Cotoneaster, Mespilus, and Pyracantha.
- This specimen is located on the east side of Lake Washington Boulevard, just north of the Boyer Parking Lot.
2) Deutzia x hybrida ‘Magicien’
- Named after Johann van der Deutz, a friend of Thunberg in 18th century Amsterdam, Deutzia contains some of the most beautiful shrubs currently in flower. It is a member of the family Hydrangeaceae.
- This specimen is located near the east side of our field nursery, along the Broadmoor fence.
3) Kalmia latifolia Mountain Laurel
- Native to eastern North America, Kalmias are a small group of shrubs within the family Ericaceae. They were named by Linnaeus in honor of Peter Kalm, one of his pupils. The Arnold Arboretum near Boston boasts a great hedge of K. latifolia that are over 200 yards long.
- These cuttings were taken from specimens on Arboretum Drive near the Woodland Garden.
4) Ostrya carpinifolia European Hop Hornbeam
- A member of the family Betulaceae, the genus Ostrya contains about ten closely related species native to various parts of the northern hemisphere. O. carpinifolia is native to southern Europe. Female catkins develop into hop-like fruits in the summer.
- This specimen is located within our Hornbeam Collection near the terminus of Foster Island Road.
5) Viburnum dilatatum Linden Viburnum
- An upright, deciduous shrub native to Japan and China, V. dilatatum is displaying its small flowers borne in domed, terminal corymbs, similar to those of ‘lacecap’ hydrangeas.
- This cutting was taken from a specimen within our Viburnum Collection, just west of the “True Ashes”.
May 18th, 2014 by UWBG Horticulturist
Selected cuttings from the Washington Park Arboretum (May 12 – May 25, 2014)
“That’s Ancient History”
1) Cedrus libani (Cedar of Lebanon)
- The Cedar of Lebanon has been prized for its high quality timber, oils and resins for thousands of years.
- It was used by the Phoenicians and Egyptians and was mentioned in the Epic of Gilgamesh.
- Because of its significance, the word “cedar” is mentioned 75 times in the Bible, and played a pivotal role in the cementing of the Phoenician-Hebrew relationship.
2) Helleborus niger (Black Hellebore, Christmas Rose)
- Helleborus niger is commonly called the Christmas rose due to an old legend that it sprouted in the snow from the tears of a young girl who had no gift to give the Christ child in Bethlehem.
- During the Siege of Kirrha in 585 B.C., Hellebore was reportedly used by the Greek besiegers to poison the city’s water supply. The defenders were subsequently so weakened by diarrhea that they were unable to defend the city from assault.
3) Laurus nobilis (Bay Laurel, Sweet Bay)
- Bay Laurel was used to fashion the laurel wreath of ancient Greece, a symbol of highest status. A wreath of bay laurels was given as the prize at the Pythian Games because the games were in honor of Apollo, and the Laurel was one of his symbols.
- In the Bible, the Laurel is often an emblem of prosperity and fame. In Christian tradition, it symbolizes the resurrection of Christ.
4) Rhododendron ponticum
- Xenophon described the odd behavior of Greek soldiers after having consumed honey in a village surrounded by Rhododendron ponticum during the March of the Ten Thousand in 401 B.C.
- Pompey’s soldiers reportedly suffered lethal casualties following the consumption of honey made from rhododendron deliberately left behind by Pontic forces in 67 B.C. during the Third Mithridatic War. Later, it was recognized that honey resulting from these plants has a slightly hallucinogenic and laxative effect.
5) Taxus baccata (English or European Yew)
- One of the world’s oldest surviving wooden artifacts is a Clactonian yew spear head, found in 1911 in Essex, U.K. It is estimated to be about 450,000 years old.
- A passage by Caesar narrates that Catuvolcus, chief of the Eburones poisoned himself with yew rather than submit to Rome (Gallic Wars 6:31).
May 3rd, 2014 by UWBG Horticulturist
Selected cuttings from the Washington Park Arboretum (April 28 – May 11, 2014)
1) Rhododendron spp. Azalea
- Azaleas are in the genus Rhododendron, with evergreen azaleas in the subgenus Tsutsusi and deciduous azaleas in the subgenus Pentanthera.
- The Olmstead Brothers originally planned for 11,000 azaleas to be planted along Azalea Way. More than 3,100 have been planted and over 2,000 remain.
- Azalea Way contains 21 species of azalea and more than 200 hybrids.
2) Tsuga heterophylla Western Hemlock
- Our native western hemlocks are currently laden with new female cones which are deep purple when immature.
- Currently, a scientific experiment is being conducted as a collaboration between the Washington Park Arboretum and the University of Massachusetts, using the collection of T. heterophylla and T. canadensis.
- We are studying the predator/prey relationships among the hemlock Wooly Adelgid, eastern and western hemlocks, and the predator species that prey on the Adelgid.
3) Syringa oblata var. dilatata, S. patula Lilac
Close-up photo of newly-forming female cone on Larix decidua
- Our Lilac Collection contains more than 14 species along with several more hybrids.
- Our primary lilac display is on Azalea Way, just south of the Woodland Garden.
4) Larix decidua, L. kaempferi Larch
- Now is a great time to admire many conifers for their display of young and old cones on the same branch.
5) Rhododendron ‘El Camino’ Halfdan Lem hybrid
- Our Puget Sound Rhododendron hybrid bed is located on Azalea Way south of our Lilac Collection.
- This bed contains plants from local hybridizers dating back to the early 1940s.
April 24th, 2014 by UWBG Horticulturist
Earth Day 2014
On Saturday, April 12th, over 220 people joined together at Washington Park Arboretum to celebrate Earth Day with SCA! The day began with Seattle mayor Ed Murray, SCA founder Liz Putnam, current SCA student Diana Furukawa, and others celebrating the day and imploring volunteers to consider the effects of climate change and to take action in their communities. SCA youth lead eight volunteer groups around the park. Together volunteers accomplished the following:
- 14,044 sq ft invasive plants removed
- 40 cubic yds mulch spread
- 205ft trail maintained (graveled)
- 94 plants potted
Check out amazing photos from the day here!
Check out the project map:
Text and photos contributed by SCA
April 24th, 2014 by UWBG Horticulturist
A mature western hemlock, Tsuga heterophylla, is scheduled for removal on Wed, April 30. It is located in Rhododendron Glen, north of the Glen pond.
- Fungal conks seen growing on the trunk is an indicator that a rot inducing pathogen is present.
- Its hazard potential is great due to extensive internal decay.
- A wild-life snag will be left in place.
Each tree requires evaluation to determine the best course of action for the site.
Conks growing on hemlock trunk
April 20th, 2014 by UWBG Horticulturist
Selected cuttings from the Washington Park Arboretum (April 15 – 28, 2014)
1) Melicytus angustifolius
- This southern hemisphere Violaceae relative thrives in rocky places in mountains or on coasts, or in evergreen forests.
- Is ‘dioecious’ or ‘of two houses’ in Greek translation; male and female flowers are present on separate plants.
2) Erica arborea var. alpina
- Found along the southern end of Arboretum Drive, this is one of the older collections in the Washington Park Arboretum, dating back to 1947.
- This form, var. alpina, is a smaller shrub, very hardy, and with brighter green foliage, making an imposing highlight among smaller heaths and heathers.
3) Poncirus trifoliata (syn. Citrus trifoliata)
- Bitter, non-edible yellow fruits that resemble a small orange
- Two large specimens in the Arboretum found in grid 8-1W and 12-B, north of the large parking lot off of Lake Washington Bouvelard.
4) Viburnum carlesii var. bitchiuense
- This spicy smelling Viburnum is the intoxicating fragrance you’ll be hit with the moment you walk out the front door of the Graham Visitor’s Center.
- Listed on the IUCN Red List of Threatened Plants in 1997, our cultivation of this plant helps to preserve a propagation source for future plants.
5) Phyllocladus alpinus
- This New Zealand conifer can photosynthesize through highly modified, leaf-like shoots called phylloclades as well as through leaves.
- The newly-formed seed cones are berry-like, with a fleshy white aril.
- Male and female flowers are separate, but borne on the same plant.
April 6th, 2014 by UWBG Horticulturist
Selected cuttings from the Washington Park Arboretum (4/1/14 – 4/14/14)
1) Berberis x lologensis
- A natural hybrid of B. darwinii and B. linearifolia originally found near Lake Lolog, Argentina in 1927
- If you can get past the thorns, enjoy the rich, spicy fragrance.
- Located in grid 14-6E near Arboretum Drive.
2) Acer tegmentosum ‘Joe Witt’
- This striped-bark maple is named for former Arboretum Director Joseph Witt.
- Located in the Witt Winter Garden and on Arboretum Drive in the Peonies.
3) Magnolia salicifolia ‘Else Frye’
- Selected by Joe Witt for its larger flowers and named for the wife of T.C. Frye.
- See Arboretum Bulletin Summer 1961, Summer 1962, and Winter 1962 for articles about this tree and the Fryes.
- The original tree is in the Magnolia Collection, grid 26-2E.
4) Magnolia x kewensis ‘Wada’s Memory’
- Part of a collection of plants purchased from Koichiro Wada in Japan in 1940.
- Selected by Arboretum Director Brian Mulligan for its unusually large flowers.
- The original tree is in grid 11-6E in the Hydrangeas.
5) Quercus suber (Cork Oak)”
Close-up photo of Quercus suber (Cork Oak)
- Evergreen oak native to southern Europe. A tree of incalculable social value, it produces the cork of
- Located in the Rock Roses on Arboretum Drive.
- This cutting includes the distinctive acorns – extremely rare in the Pacific Northwest.
March 21st, 2014 by UWBG Horticulturist
Selected cuttings from the Washington Park Arboretum (March 17 – 30, 2014)
1) Acer rubrum (Red Maple)
- Specific epithet, rubrum (red), refers to foliage in fall; however, flowers are red too
- One of the earliest trees to flower, appearing in March, well before the leaves
- Located at south end of Arboretum Drive East, against the Broadmoor fence
Close-up photo of the Acer rubrum (Red Maple) flowers
2) Camellia japonica ‘Jupiter’
- Carmine-red flowers with prominent yellow stamens on white filaments
- Located along Ridgetop Trail at head of Rhododendron Glen
3) Chaenomeles sp. (Flowering Quince)
- Old-fashioned, early spring flowering shrub
- OK, so this specimen is not the reddest available, but the best I could find.
- Located behind the Stone Cottage along the public path
4) Grevillea victoriae (Mountain Grevillea)
- This proteaceous plant’s foliage was the feature cutting for the first half of March 2014; now it’s the red flowers.
- Located in the Pacific Connections – Australia Entry Garden
5) Rhododendron strigillosum
- Early maroon-red flowering rhododendron
- Twigs and leaf stalks on young growth covered with long bristles
- Specimens located in the Witt Winter Garden, Woodland Garden and Sino-Himalayan Hillside
March 20th, 2014 by UWBG Horticulturist
Most visitors experiencing the beauty of our historic Azalea Way flowering cherries from now through May probably have no idea of how intensive maintaining their health and prolonging their longevity truly is for the UW Botanic Gardens horticulture staff. Just ask our Integrated Pest manager, Ryan Garrison. Ryan with staff support spends many a day throughout the year monitoring and controlling the numerous diseases and insect pests our 175 plus cherries are prone to suffer from. Our rainy climate doesn’t help one bit either, especially when dealing with our most notable disease during blossom time; a fungus known as Cherry Blossom Brown Rot. Yucko! The good news is any new cherries we plant need to show a reasonable level of resistance. The not so good news is many of our older earlier bloomers, the ones extremely susceptible to the brown rot fungus, need to be protected with fungicide applications during their bloom period. As with all of our pest issues, we start with cultural and mechanical control efforts before resorting to chemical controls. The following Integrated Pest management (IPM) program discusses our best management practices for the control of blossom brown rot. If you are interested in planting cherries for your home garden, I’ve included a list of cherries recommended for our PNW climate. All have good to excellent resistance to blossom brown rot.
14 new cherries will be planted along Azalea Way, Spring of 2014! Thanks to the UW being awarded funds from the Nationwide Cherry Blossom Tree Planting Initiative grant co-sponsored by the Consulate-General of Japan in Seattle and other supporting local community organizations.
Cherry Blossom Brown Rot - causal fungal agent known as Monolinia fructicola. The fungus overwinters on infected twigs and dried fruit on the tree or ground. The fungal spores are spread in the spring by wind and rain through the blossoms, causing twig dieback. As part of the UWBG IPM program, moving toward our goal of eliminating the use of all synthetic pesticides is our ultimate goal.
IPM relies on many strategies to manage plant health care.
- Proper ID of the pest and its life cycle
- Regular monitoring of the plants
- The use of physical, mechanical, cultural, and biological controls
- Chemical controls used as a last resort*
- Least toxic chemicals used
* All spray applications are in compliance with WSDA pesticide regulations. Sign postings are located at all entrances and Graham Visitor Center. Spray applications are scheduled based on timing and weather. We do our best to apply when public are not present. For more information, pls contact, David Zuckerman at 206-543-8008 or email@example.com
The cherries are pruned in early fall to remove infected twigs and improve air circulation. Tree rings are given a fresh coat of mulch in the fall to bury any infected plant material that may be on the ground. In our Cherry Replacement program we are only using cultivars that are resistant to Blossom Brown Rot.
Cherries recommended for the PNW:
- Prunus‘Berry Cascade Snow’
- Prunus ‘Kwanzan’ syn. ‘Sekiyama’
- Prunus‘Pink Flair®’
- Prunus‘Royal Burgundy’
- Prunus‘Snow Goose’
- Prunus subhirtella var. ascendens
- Prunus x yedoensis ‘Shidare Yoshino’