New Plantings in the Arboretum THE YEAR IN REVIEW T EX T BY R AY L A R SON P HO T OS BY N IA ll D UNNE 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 species 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 genus 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 plants 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 leaf 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 flower.. 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 Sichuan, China 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 shrub’s willow-like leaves emerge in bronze and burgundy before turning a glossy dark green, and its white, late-spring flowers 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 plant’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 as V. 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 Hubei, 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 deciduous species. flowering upright shrubs 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 maple), 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 Vietnam. 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 trees 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 sepals, 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 soils and was, histori- with the disease resistance of the East Asian cally, one of the brighter and drier sections of the species.