August 20th, 2014 by UWBG Horticulturist
Arboretum Tree Removal Notification:
The week of 8/25/14, UWBG tree crew will embark on a project located in the Winter Garden (read about project below).
4 western red cedars will be removed due to negative impact to plant collections and garden encroachment.
All pedestrian path detours and other safety considerations will be handled by tree crew.
If possible, cedar logs will be salvaged for future park uses.
UW professor of landscape architecture and designer of our Winter Garden (1987), Iain Robertson, states it’s time to open up the “room” that has been closing in on the Winter Garden for over 25 years. Continuous growth of the “living walls”, predominantly western red cedars, is now negatively impacting many of the garden’s choice plant collections. Due to this encroachment, the garden “room” is feeling confining. Judicious consideration and deliberation has led to the following curation and horticultural decisions.
- Removal of 4 western red cedars to provide needed light and future growing space for plant collections. In all cases, the “room’s walls” will expand, yet filled in by existing trees in the background to continue to provide the experience of being in an enclosed space.Pruning of several other cedars to provide light and future growing space for plant collections.
- 2 on the west side in the “twig bed”
- 1 on the south side next to the Chinese red birch grove
- 1 on the east side growing over several camellias and other collections
August 8th, 2014 by UWBG Horticulturist
Does anyone reading this know where our arboretum’s “lost” Enkianthus grove is located? By “lost”, I mean extremely well-hidden under a dense canopy of western red cedars and other trees.
Enkianthus specimens previously “lost” in the overgrowth.
Enkianthus are shade-tolerant shrubs, but NOT “black-hole” shade tolerant. Like most living plants, they do need light to grow and thrive. It’s a bit embarrassing, but I can honestly say, during my 30 plus year tenure on the UWBG horticulture staff, I don’t recall ever working in the area for longer than maybe a day cleaning up after a storm or pruning a few of the bigger trees. And, we definitely did not pay any attention to the main attraction – a grove of over 50 Enkianthus specimens, mostly all E. campanulatus (red-vein enkianthus) and over 70 years old! Well, the answer to the question above is Rhododendron Glen, encompassing several grid maps (14-2E, 14-3E and 15-3E).
Accession number 2352-37, this Enkianthus campanulatus was planted in 1937.
Now for the good news. Thanks to funding designated for Rhododendron Glen, our horticulture staff has taken on the project to restore the grove for all to be able to once again, after a very long hiatus, enjoy its natural beauty and splendor throughout the year.
The project scope includes the following to improve the health and display of the Enkianthus grove:
- Increase light conditions through selective understory brush clearing, tree removals and pruning
- Open view corridors and a cleared natural pathway for visitors to walk from the upper Rhododendron Glen pond area down to the lower “Lookout” pond
- Improve health of the Enkianthus through practicing sound horticulture: mulching, watering and fertilizing the grove
For more information about the ornamental shrub, Enkianthus campanulatus, go to Wikipedia website below:
July 12th, 2014 by UWBG Horticulturist
Selected cuttings from the Washington Park Arboretum (July 7 – 20, 2014)
1) White Ash (Fraxinus americana)
- Tough, plentiful, and easily bent into curves, Ash is used in tennis racquets, billiard cues, skis, and baseball bats.
- White Ash is native to eastern and central North America.
- This cutting is from the cultivar ‘Rose Hill’, located in grid 47-3E near the Lagoons.
2) Common Box (Buxus sempervirens)
- Used for crocquet balls because of its hardness.
- Native to Europe, northern Africa and western Asia.
- The cultivar here is ‘Argentea’ from grid 5-B in our Boxwood Collection.
3) American Hop Hornbeam (Ostrya virginiana)
- The first ice hockey sticks were made from the dense wood of this small tree in the mid-19th century until the 1930s by the Mi’kmaq people of Nova Scotia.
- Ostrya virginiana is native to eastern North America.
- The Arboretum has two trees in grids 19-3W and 24-4W.
Close-up photo of Persimmon flowers
4) Persimmon (Diospyros virginiana)
- The “woods” of golf (drivers, not Tiger’s) were typically made from this American member of the ebony family from which it inherits its extreme density.
- Persimmon is most common in the southeastern United States.
- In the Arboretum, they are in grids 12-1W and 12-2W, north of the Boyer Street parking lot.
5) Sugar Maple (Acer saccharum)
- Commonly called “rock” maple by those who value its hardness and smooth grain.
- This native of eastern North America provides wood for bowling alleys, bowling pins, basketball courts, and baseball bats.
- The Arboretum has several cultivars in various locations.
June 29th, 2014 by UWBG Horticulturist
Selected cuttings from the Washington Park Arboretum (June 23 – July 6, 2014)
1) Erhetia dicksonii
Close up photo of Ehretia dicksonii inflorescence
- Ornamental tree from Asia with corky bark and fragrant white terminal cymes.
- Located along path heading up to Rhododendron Glen from Azalea Way, grid 15-1E.
- Go to link below for thorough description and uses.
2) Holodiscus discolor (Ocean Spray)
- My favorite summer flowering Pacific Northwest native deciduous shrub.
- In full flowering, cascading glory now throughout our native matrix.
3) Hypericum henryi ssp. uraloides
- The really big Azalea Way flower show may be over, but now it’s Hypericum time.
- This shrubby St. John’s wort is a huge attractant of many kinds of bees.
- Located in east-side bed J, midway down Azalea Way, grid 20-1W.
4) Illicium henryi (Henry Anise Tree)
Close up photo of Toona sinensis leaves and inflorescence
- A handsome evergreen woodland shrub or small tree from China.
- Waxy, bright rose-colored flowers. Leaves and star-shaped fruit give off a scent of anise when crushed.
- Located along forested Ridge Trail within the Asiatic Maple section, grid 25-1E.
5) Toona sinensis (Chinese Cedar)
- You can Toona piano, but you can’t Toona fish . . . or in this case, a tree.
- Deciduous tree from eastern and southeastern Asia with pinnately compound leaves and white flowering panicles in summer.
- Located in north Pinetum, grids 44 and 45-6W. For cultural, medicinal and commercial (timber) importance, go to link http://en.wikipedia.org/wiki/Toona_sinensis.
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