New Plantings in the Arboretum THE YEAR IN REVIEW

T e x t b y R a y L a r s o n P h o t o s b y N i a ll D u n n e

The bright red fruits of the tea viburnum (Viburnum setigerum) in the main Viburnum Collection.

t was another busy year for collections development and planting in the Arboretum—with a few long-planned projects completed and others started, and with many smaller additions made throughout the gardens. Despite some Isetbacks due to the prolonged deep freeze and heavy snows in February, it was a positive year overall, with some notable improvements.

INVIGORATING THE VIBURNUMS and other re-introduced after having The Viburnum Collection is located to the west been impacted by the trail construction. of the Puget Sound Rhododendron Hybrid The Viburnum Collection is a core part of one Garden, in between Azalea Way and the of the Arboretum’s original taxonomic plantings Arboretum Loop Trail—and its gravel paths form from the 1930s and 1940s. In those days, the the only east-west connectors between the two Viburnum belonged in the Caprifoliaceae, major trails in that part of the Arboretum. Long or honeysuckle family, along with Lonicera one of our most comprehensive collections of a (honeysuckle), Weigela, Deutzia, Sambucus particular genus, the viburnums have recently (elderberry), Kolkwitzia (beautybush), Abelia and received some much-needed refreshment. Since others. Many from these genera can be the completion of the Loop Trail in late 2017, the found growing near the viburnums, especially collection has been pruned, thinned of excess and on the north side of what has historically been overgrown specimens, and—in the past year— called “Honeysuckle Hill.” In recent taxonomic expanded. Three phases of planting occurred in revisions, however, both viburnums and elder- the winter and spring, with new species added berries have been moved to the Adoxaceae

Winter 2020 v 3 (moschatel family), a much smaller family that also has opposite arrangement. (This type of family name shifting is one reason why laying out entire public gardens according to taxonomic theme has become outmoded.) The evergreen Viburnum awabuki ‘Chindo’ in .. While viburnums have fallen somewhat out of horticultural favor in recent decades, they are a large group comprised of many very useful and In three of the new beds, we added large attractive species. My goals with this collection examples of the wild-collected evergreen species have been to increase species diversity, grow Viburnum henryi. Two of these were transplanted more plants propagated from wild-collected from a shaded area along Azalea Way, while the seed, and showcase additional evergreen other was generously donated by local horticul- examples that are less familiar to the public. turist Riz Reyes from his former home garden. While the construction of the Loop Trail did All three of the plants are progeny of seed that affect some of the original plantings (which we Riz collected in , back in 2004, propagated for reintroduction), overall it has while an undergraduate student in the old UW helped us make improvements. Along with being Urban Horticulture program. Riz also donated somewhat out of the way, the old viburnum area a large example of Viburnum propinquum, grown had become very shaded over time. The Loop from seed collected during that same trip. The Trail not only made the collection more acces- plants are settling nicely in their new home, and sible to visitors, it also increased light exposure the new growth should be especially attractive to existing plants. Viburnums prefer sunnier next spring. conditions, and the trail has resulted in increased Viburnum henryi has long been one of my flowering and better fall color. favorite members of the genus. In 2006, I planted a two-gallon specimen—also from Riz—at the UW president’s residence and, over the years, have always been impressed with its attractive performance. The ’s willow-like emerge in bronze and burgundy before turning a glossy dark green, and its white, late-spring have a light honey scent. The species grows best in full sun in our climate and reaches six-to-eight feet tall in maturity

The yellow-fruited linden viburnum (Viburnum dilitatum in bright condi- ‘Xantocarpum’) planted in new beds along the Loop Trail. tions. In 2005, I planted another The trail also opened up some new oppor- specimen in my tunities for expanded planting beds. Using parents’ garden funds from a generous donor to the Arboretum in a shadier Foundation, we added new berms and beds north situation, and it of the existing collection along the trail. This has performed allowed for the planting of new species, as well steadily with little as many of the re-propagated plants. Another special care. But added benefit of the trail has been increased sun is where it visibility into the Viburnum Collection from Lake does best, and I chose bright Washington Boulevard. Fragrant snowball (Viburnum x carlcephalum) in bloom by the Loop Trail. 4 v Washington Park Arboretum Bulletin positions along the Loop Trail to highlight the these were propagated from existing ’s charms. plants prior to trail construction, but we also Elsewhere, we planted several other evergreen included some new acquisitions. We replanted types, including Viburnum awabuki ‘Chindo’— a several shrub honeysuckles, including Lonicera selection originally collected on Chindo Island, purpurascens, a Himalayan species that features South Korea. Along the trail in the origi- burgundy-tinted flowers and seems to be absent nal collection area, we planted Viburnum aff. from other arboreta in the U.S. We also replanted atrocyaneum (recently confirmed asV. propinquum) L. insularis, L. ferdinandii, L. discolor and others. from a Far Reaches Farm collection expedi- Unlike in parts of the eastern U.S., most shrub tion to , China. Closer to the Boulevard, honeysuckles have not shown invasive tenden- one of Dan Hinkley’s collections of Viburnum cies in the Pacific Northwest. cylindricum—a large-growing species native to We planted groupings of Weigela maximowiczii Southeast Asia—was added, along with several and W. japonica var. sinica, which are profusely species. flowering upright with creamy-yellow Examples of the deciduous species Viburnum and pink flowers, respectively. We also added cotinifolium, V. betulifolum (birchleaf viburnum), V. the white-flowering Deutzia × magnifica ‘Erecta’, dilatatum (linden viburnum), V. lantana (wayfar- which boasts handsome peeling bark and double ingtree viburnum), V. parvifolium, V. prunifolium flowers along arching stems. Rounding out the (blackhaw), V. setigerum (tea viburnum), and show are two different varieties of Philadelphus several others were interspersed along the trail coronarius (sweet mock orange), a P. coronarius as part of a planting of more than 50 individual hybrid, and a golden-leaved selection, ‘Aureus’. specimens. We also added three evergreen companions for Providing some contrast to the viburnums texture and structure: the conifers Chamaecyparis in this area, we planted a wild-collected Acer taiwanensis and Cephaloptaxus fortunei, and the saccharum var. leucoderme (chalk ), a broadleaf evergreen Phillyrea angustifolia var. southern variant of the sugar maple that’s shorter rosmarinifolia, an osmanthus relative. than its northern cousin but features the same Planting in this area was supported by several outstanding fall color. We also planted a speci- volunteer work parties from the Seattle office men of Magnolia aff. insignis, grown from seed of the company DocuSign, as well as continued collected by Dan Hinkley in the mountains of major donor support for our Lake Washington northern . Boulevard and Loop Trail improvements.

HONEYSUCKLE ARBORETUM CREEK PROJECT FAMILY Thanks to the same donor, another large project Just a bit to the occurred along the Lake Washington Boulevard north of the corridor: the planting of an area of mostly native Viburnum species adjacent to Arboretum Creek—on the Collection, west side of the road, opposite the Viburnum along the trail Collection. Over many months in 2018 and on the east side 2019, invasive plants were removed from this of Yew Hill, we area, existing shrubs and were pruned, and refreshed mulch was laid down. another newly This project enabled us to complete the first opened-up area round of native plantings between the Boulevard with plants from and Creek in January. Here we installed the honeysuckle many tough but attractive species, includ- family. Most of ing Philadelphus lewisii (western mock orange), Acer circinatum (vine maple), Holodiscus discolor Fruits of Lonicera purpurascens in the Honeysuckle Collection. Winter 2020 v 5 from China with white blossoms and purple , will close out the flowering in late June. Quercus rugosa, a small, hardy evergreen oak from the southern U.S. and Mexico, provides a backdrop to the new bed, while expanding the species diversity of the adjacent Oak Collection. Orange flags marking new native-shrub plantings The plantings are relatively small now, but over along Arboretum Creek. the next few years will fill out and become more prominent at this busy intersection. (oceanspray), Physocarpus capitatus (Pacific ninebark), and Malus fusca (Pacific crabap- MEDITERRANEAN MAGIC ple), along with a few conifers such as Tsuga Early spring also saw additions to the heterophylla (western hemlock) and Thuja plicata Mediterranean Garden—a small collection of (western red cedar). Adjacent to the Boulevard, plants native to Mediterranean regions around we planted two larger examples of ‘Starlight’, a the world, originally developed in the late 1940s. hybrid of Cornus nuttallii (Pacific dogwood) and Located along Arboretum Drive, just south of C. kousa (Kousa dogwood) that combines the the Fiddleheads Forest School, this area has shape and large flowers of our native dogwood relatively well-draining and was, histori- with the disease resistance of the East Asian cally, one of the brighter and drier sections of the species. We plan to add more ornamental Arboretum. Over the years, however, the garden shrubs and trees to the vicinity this winter, has become shaded by the continued growth of now that additional areas have been cleared of nearby conifers. Beginning in 2015, some trees invasive plants. at the south and west sides were thinned to let in more light, and the sun-loving Mediterranean BOULEVARD & FOSTER ISLAND ENTRY species have benefited. Also as part of the larger Lake Washington We’ve also added several new plants, Boulevard Corridor project, we planted a new donated by the Arboretum Foundation from its bed along the Loop Trail next to where the Mediterranean-themed display garden at the Boulevard intersects with Foster Island Road. 2019 Northwest Flower and Garden Festival. We The semi-circular bed stretches back from incorporated two olive cultivars, Olea europaea the rock work on the east side of the trail and ‘Manzanillo’ and ‘Mission’, near the O. europaea will add a long season of late-winter to early- ‘Frantoio’ that was installed in 2016. While the summer interest at this Arboretum entry plants are settling in well so far, it might be several point. We planted two specimens of the late- years before we can offer “Arboretum Olive Oil” winter bloomer pauciflora (buttercup in the Gift Shop to complement the Arboretum winterhazel) along the rockery, plus three Honey! Cupressus sempervirens ‘Glauca’, a cultivar early spring-blooming Camellia japonica of the Italian cypress, was also added. ‘Showa-no-Hikari’. This camellia bears single, yellow-centered, whitish-pink flowers streaked PACIFIC CONNECTIONS ENTRY GARDENS with dark-pink patterns. We continued to add plants to the Pacific Next to bloom in the bed are three Connections Garden, including new species Rhododendron ‘Wilbrit’, an older, moderate- in all five of the entry gardens surrounding the sized cultivar featuring dark-green, rounded central meadow. To provide more evergreen leaves and pink flowers.Rosa wardii var. culta, a interest and contrast in the Cascadia Entry single-flowered, creamy-white shrub rose (also Garden, we planted two cultivars of our native growing in the larger bed just to the southeast) hemlock species, Tsuga mertensiana (mountain will continue the bloom season. Finally, two hemlock) and T. heterophylla (western Philadelphus purpurascens, a mock orange species hemlock). ‘Iron Springs’ is a dwarf version of 6 v Washington Park Arboretum Bulletin dark and twiggy Pittosporum crassifolium— a new species for us—were added as well. (I Drimys winteri var. chilensis blooming along continue to be impressed with the diversity the Loop Trail in Pacific Connections. of the Pittosporum genus, and especially with species from New Zealand.) the western hemlock with a more open AN EXPANDED AUSTRALIA DISPLAY form than the straight The biggest addition to Pacific Connections species. (An example Garden—since the 2013 planting of the New of the original 1968 Zealand Forest—was a major expansion of the introduction of ‘Iron Australia Entry Garden, which took place in late Springs’ can be May. This was the result of a generous donation found in the rockery from Daniel Springer in honor of his mother, south of the educa- longtime Arboretum volunteer Jenefer Hutchins. tion greenhouse by The vehicle turnaround just north of the main the Graham Visitors Australia Entry Garden bed was largely devoid of Center; another plantings since the creation of the New Zealand grows in the hemlock Forest and, in recent years, the area’s two grove in the Magnolia major native trees—a bigleaf maple and Pacific Collection.) madrone—had either severely declined (in the ‘Sherwood Compact’ case of the former) or died (the latter), partly 'Ada Hoffman' blooming in the is a slow-growing, due to construction impacts. The other signifi- Chile Entry Garden. blue-foliaged cant plantings in the area—two majestic Parrotia cultivar of the mountain hemlock. We also persica (ironwood) within the turnaround— planted Acer circinatum ‘Sunglow’, a golden- had remained in excellent condition and were leaved selection of our native vine maple, in a retained. The rest of this area, along with the recently expanded section of the Cascadia Entry northern half of the bed on the south side of Garden along Arboretum Drive. the turnaround, were planted with species and In the Chile Entry Garden, we added three cultivars native to Australia. From the earli- specimens of Crinodendron hookerianum (Chilean est planning of Pacific Connections, this area lantern ) and one of the cultivar C. hookerianum had been imagined as an expansion of the Entry ‘Ada Hoffman’. Both are small evergreen trees Garden, showcasing Australia’s many garden- that bear stunning lantern-shaped flowers in worthy plants. spring and summer—red on the straight species and light pink on the cultivar. In the China Entry Garden, another winter- Eucalyptus and blooming Callistemon in the newly expanded blooming Edgeworthia chrysantha ‘Nanjing Gold’ Australia Entry Garden. was planted closer to the path; a narrow-growing selection of the dove tree, Davidia involucrata ‘Iseli Fastigiate’ was added north of the inter- pretive shelter; and Viburnum cylindricum was planted in a tough spot on the southwest side of the shelter to close off an unwanted social trail. The New Zealand Entry Garden also saw some additional plantings of Olearia × haastii and Podocarpus nivalis. Three specimens of the

Winter 2020 v 7 Three different smaller Eucalyptus trees— conifers into the E. parvula, E. rubida and E. perriniana—were display. This rare installed to anchor the adjacent plantings of many conifer species is forms and selections of , Callistemon endemic to the (bottlebrushes), Leptospermum, Podocarpus and Siskiyou Mountains Tasmannia, as well as examples of Prostanthera in southwest cuneata (alpine mint bush), microcarpa Oregon and the and myricoides. Over one hundred plants northern ranges of were installed, and they are settling in. California. It has Western spice bush The floral display will start in early fall— a weeping habit (Calycanthus occidentalis) with many of the Grevillea selections blooming when mature. We in bloom in late summer. through the winter—and then continue in have one larger spring and summer with the red, yellow and example that was planted in the Entry Garden lime-green flowers of the bottlebrushes. Alpine ten years ago and are looking forward to having mint bush—on the Great Plant Picks list (www. a small grove of this iconic conifer alongside greatplantpicks.org) for the Pacific Northwest— other mid- and higher-altitude evergreens in will chime in from late spring to early summer the forest garden. with small, orchid-like white flowers. So will Also along the northern portion of the the alpine tea trees Leptospermum rupestre and forest, we planted several additional Calycanthus L. namadgiensis, with their profusions of white occidentalis (western spice bush), Gaultheria flowers. It should be quite a show in the coming humifusa (alpine wintergreen), and Quercus years as the plants fill in. vacciniifolia (deer oak). In the southern half of Further plantings in the fall of 2019 near the forest garden, we added some Cercis occiden- the east and northern edges of the turnaround talis (western redbud) and Amelanchier alnifolia included , Eucalyptus perriniana (western serviceberry), along with examples of and E. parvula. Later in 2020, once they grow Arctostaphylos and Ceanothus. Two other new a little larger in our nursery, we will begin to additions are the large herbaceous perennial add more specimens of snow gum (Eucalyptus Aralia californica (elk clover), which features pauciflora var. niphophila). ball-like clusters of white summer flowers and dark-purple fall berries, and the dwarf silk PACIFIC tassel, Garrya buxifolia, which grows to about half CONNECTIONS the size of its coastal cousin, Garrya elliptica. We FOREST hope to plant many more of these two in the near PLANTINGS future, as they are common components of the The Pacific Siskiyou region. Connection forest In the Gateway to Chile, we planted more displays also saw wet-tolerant species that can handle the seeps the addition of and clayey soils of this area. Two Podocarpus many new species. salignis (willow-leaf podocarp) and a Fitzroya In the Cascadia cupressoides (alerce) were added to bare areas Forest, near the on the slope, along with several Gunnera tincto- circular stone bench ria and G. magellanica. These species have proved at the garden’s high more adaptable to the wet conditions than some point, four Picea of the original plantings of 2010. Podocarpus 'Iron Springs' western breweriana (Brewer’s salignis, in particular, has impressed us with its hemlock in the Cascadia Entry Garden. spruce) were planted unusual evergreen texture—more like the tropi- to bring more cal members of the genus—and its moderate,

8 v Washington Park Arboretum Bulletin attractive growth. An Araucaria araucana wetlands along the Loop Trail. Like its American (monkey puzzle) was added to a drier position cousin, N. sinensis also produces outstanding fall in the rockery near the benches at the northeast color and can tolerate wetter soils. corner of the Gateway, along with the large, late Several trees re-propagated during the summer-flowering perennialLobelia tupa. Loop Trail project, including the crabapples Farther to the northwest, along the Loop Trail, Malus × spectabilis ‘Riversii’ and Malus baccata several more Chilean species were added to help ‘Pyramidalis’, were planted between Lake fill in areas exposed during trail construction. Washington Boulevard and the Loop Trail, just These included two Drimys winteri var. chilensis, north of the expanded parking lot 19 (the “Birch along with Azara alpina, a lower-growing Lot”). A hornbeam from Taiwan, Carpinus member of this genus of attractive broadleaf kawakamii, was added to the hornbeam area west evergreens—and another new species for us. of Duck Bay, and another Taiwanese species, A little farther north along the trail, in the Sorbus randaiensis, was planted in the Brian future China Forest, we added more plants Mulligan Sorbus Collection. Both these speci- native to Emei Shan, in Sichuan Province. This mens were grown from seed collected in the wild included two maple species, Acer campbellii ssp. by Dan Hinkley. flabellatum and A. davidii, as well as an attrac- Cyclocarya paliurus (wheel wingnut) was tive birch, Betula aff. utilis, with reddish-brown added to the collection just north of Yew peeling bark. All three are from various collect- Hill. And Alniphyllum fortunei, a spring-flower- ing trips by Dan Hinkley. New understory plants ing relative of Styrax—another donation by Far include Helwingea chinensis, Mahonia (Berberis) Reaches Farm, based in Port Townsend—was gracilipes, and Stachyurus aff. retusus. planted in upper Rhododendron Glen among We added many new plants to the larger New a grove of hydrangeas and rhododendrons, Zealand Forest—the fruits of previous seed- overlooking the seasonal stream. collecting efforts in that country—and we’ve been acquiring additional examples of existing plants DANIEL J. HINKLEY ASIAN MAPLE that have performed well in that garden. We are COLLECTION also excited to have several species of plants With fall rains arriving early in September, from graduate student Kyra Matin’s spring 2019 planting was able to resume in earnest. The collecting work in New Zealand now germinating first installations occurred in the Asian Maple (see page 25). We hope to begin planting these Collection, in anticipation of its dedication in out in the next year or two. October to renowned plantsman and major Arboretum supporter Dan Hinkley (see page 16). A SAMPLING OF NEW TREES It is fitting that Dan joins two other profound Spring planting in the Arboretum concluded contributors to the Arboretum—Brian Mulligan with the addition of many trees throughout the (Sorbus) and Joseph Witt (Winter Garden)— grounds, including two specimens of Nyssa in having collections named after him. sinensis—an Asian relative of the southeast We planted five new trees in the main collection U.S. native, N. sylvatica (black tupelo)—in the area. Three of them were grown from seed collec- tions made in recent years by Dan: Acer henryi, from The new semi-circular planting bed at the intersection of Lake Hubei province, China; and A. aff. caudatifolium Washington Boulevard and Foster Island Road (see page 6). and A. serrulatum, from the mountains of Taiwan. Also new to the area are selections of Acer pentaphyllum and A. davidii ssp. grosseri. As companion plants for the , we added wild-collected examples of Hydrangea aspera and H. longipes from Dan’s expeditions.

Winter 2020 v 9 REJUVENATING RHODODENDRON GLEN One area where several other Mahonia × savilliana were planted in the fall is Rhododendron Glen. The Glen has seen a lot of changes this past year, and many more are on the way—thanks to a generous gift from Mary Ellen and Gordon Mulder (see “Restoring Rhododendron Glen,” by Jane Stonecipher, “Arboretum Bulletin,” Spring 2019). While planning for larger improvements to the Glen’s upper pond and creek is well under way, immediate progress to planting areas has been ongoing since last February. Hydrangea longipes in the "China Wedge" In the upper Glen, increasingly dense canopy at Pacific Connections. had reduced flowering in many prized understory plants and led to the loss of others. In June, after Both have attractive lacecap flowers and large, careful planning—including consultation with fuzzy leaves. rhododendron experts—we thinned some trees

HEIGHTENED HYDRANGEA We planted hydrangeas in other parts of the Arboretum this fall, too. In the main hydran- gea section, within the Camellia Collection, we continued to add several Hydrangea macrophylla, H. serrata, and H. aspera varieties. One that I’m particularly impressed with is Hydrangea macro- phylla ‘Jogosaki’, a double-flower lacecap type that features lilac florets that bloom over a long The round-leafed Rhododendron williamsianum period. This is planted adjacent to the Franklinia in Rhody Glen. alatamaha along Arboretum Drive and should and removed some others. A few trees were left as reach six feet tall in time. snags to support wildlife habitat and the growth In the so-called “China Wedge,” where of flowering vines. The increase in light has been the main, descending trail of the New Zealand dramatic, and many of the mature plantings are Forest does a final switchback north towards the now more visible. Lookout Gazebo, we planted more specimens of During the spring and summer, invasive Hydrangea aspera and H. longipes to complement plants such as bindweed were removed, and existing plantings native to Emei Shan. other rampant growers such as Vinca minor were These join other new plantings native to reduced. Rockeries were uncovered, and other that mountain, including Viburnum betulifolium declining plants were removed or pruned. and Mahonia (Berberis) × savilliana. The latter is In the fall, we got down to some serious a naturally occurring hybrid between Mahonia planting business in the upper part of the Glen. (Berberis) gracilipes and M. eurybracteata. Readers Here we have added several large-leafed of my 2018 “year in review” column might Rhododendron species such as R. rex and R. sinofal- remember me mentioning we had seedlings of coneri. Species newer to cultivation, including this hybrid in our nursery, and I’m excited to the blue-green-leaf species R. yuefengense and R. add the plant’s attractive, blue-green foliage platypodum, were planted in groups—along with and late-summer flowers here—and to various companion plants such as Mahonia eurybracteata, plantings in the Arboretum. a late-spring bloomer with blue-green foliage,

10 v Washington Park Arboretum Bulletin After removing bindweed and periwinkle from Rhododendron Glen, we installed new specimen shrubs and woodland plants.

M. × savilliana, and several fern species. Other TOP LEFT: New planting of Beesia calthifolia blooming rhododendron plantings included R. williamsia- in Rhody Glen. num, with its compact habit, rounded foliage, and rose-pink flowers; and R. orbiculare, a RIGHT: Mahonia × savilliana in Rhody Glen. larger-growing species with near-circular leaves and pink flowers. The Rhododendron Species Botanical Garden in Federal Way, Washington, very gener- SEED COLLECTION ously donated many of these plants, and we look IN THE SISKIYOUS forward to adding to the diversity and breadth of the collection in the next year. Dan Hinkley also donated new rhododendron species from his collecting trips, along with many companion plants. In addition, Far Reaches Farm contrib- uted many other woodland perennials, shrubs and small trees to the project. We are fortunate to Photo courtesy Joe Abken have such a generous and knowledgeable horti- cultural community in the region. Other than In early October, the UW Botanic Gardens under- private donations, the UW Botanic Gardens has took a joint seed-collecting trip in the Siskiyou no dedicated funding for plant acquisition, and Mountains with representatives from the we are grateful to our donors—including these Heronswood Garden in Kingston, Washington and other gardens and nurseries—for support. and the Kruckeberg Botanical Garden in Shoreline, The Rhododendron Glen project is one of the Washington. Pacific Connections Garden horticul- most exciting collections projects in recent years, turist Joanna Long joined me, Heronswood curator and I’m very much looking forward to continued Nathan Lamb and taxonomist Ross Bayton, and development and enhancement of the area. Be Kruckeberg executive director Joe Abken on the sure to visit often to check on the progress of this five-day sojourn. and other gardens. We appreciate your contin- We gained valuable insights into the flora and ued support and hope you visit and enjoy the landscapes of the area and collected seed from Arboretum throughout the year. more than 90 different taxa. With help from these partners, we will be growing the plants on in the Ray Larson is curator of Living Collections at the coming years for inclusion in the Cascadia Forest. University of Washington Botanic Gardens and We are excited to add more diversity of species to curator of the Otis Douglas Hyde Herbarium, the display, and to establish a closer approximation the Arboretum’s herbarium housed in the Center of the landscape character of the Siskiyous. It was a for Urban Horticulture. very successful and informative trip. m

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