We always take a tree walk or two when we attend national conferences. Many of the bare root and container liners sold to our customers are grown on to landscape-ready size and planted in big cities like San Francisco, Seattle, Chicago, and New York City. Regardless of destination, each tree planted contributes to the beauty and livability of these great urban centers.
The Women in Landscape Architecture Walk (WILA) took participants past many remarkable trees that soften the hard edges of downtown San Francisco. Thanks to our many fine customers in Northern California, we found a good number of trees that may well have taken root right here in Boring – Lindens, Ginkgoes, Hornbeam, River Birch, etc. More than 100 walkers joined the annual walk via Zoom audio and earbuds that made it possible to hear every word spoken by our tour guides. As was the case at last year’s WILA Walk in Nashville, it was inspiring and very informative to hear from women landscape architects who led or took part in SOMA district landscape projects large and small.
Trees profiled here are currently available, as noted in the descriptions. Space here is limited, but you can find more images from our San Francisco ramblings on our Facebook and LinkedIn pages. We invite you to join us there!
Greenspire® Linden
Tilia cordata ‘Greenspire’
Proven workhorses of the urban forest, Lindens continue to prove themselves as top performers and contributors to the urban canopy, regardless of geography. Spotted on the WILA walk, these appear to be Greenspire® Lindens that are delivering bright yellow fall color along with their many ecosystem services. The standard of comparison among the Lindens, this 1961 introduction of Princeton Nursery is undoubtedly the most widely planted cultivar, and for good reason. It has a strong central leader, very uniform branch arrangement and maintains a symmetrical, pyramidal form as it reaches a height and spread of about 40’ x 30’. (Bare root, container, NWST)
Rotundiloba Sweetgum
Liquidambar styraciflua ‘Rotundiloba’
Glossy, bright green leaves are thick and deeply lobed, with rounded tips rather than sharply pointed as is typical of the species. Fall color ranges from yellow and orange to red and purple tones. Pyramidal form and medium stature of 45’ tall x 25’ wide at maturity make it a pedestrian and traffic-friendly option. The only sweetgum generally regarded to be completely fruitless, it has occasionally been observed to produce a few fruits. In general, it is an ideal candidate for city streets where fruit might be messy or inconvenient and where growing conditions call for a tough urban performer. (B&B and NWST)
Presidential Gold® Ginkgo
Ginkgo biloba ‘The President’
Though we don’t know the cultivar of the Ginkgoes pictured, we’re certain that Presidential Gold® Ginkgo would be an ideal candidate for this Rincon Place streetscape and other urban sites. Outstanding in the nursery row and then in the landscape, this robust selection offers a strong central leader and full branching at a young age. As it matures, it develops a dense upright crown and a broadly pyramidal to oval shape. Fall color of this seedless male selected by Dr. Michael Dirr is bright yellow in the fall.
Typical of the species, it thrives in city growing conditions. In general, ginkgoes are tolerant of compacted soils (acid or alkaline) and aren’t bothered much by air pollution, heat or cold, diseases or pests. Trees growing in this park designed by Pamela Burton & Co. demonstrate that ginkgoes perform well in urban canyons that are shaded by tall buildings for much of the day. (Bare root, container, VigorLiner® and NWST)
Heritage® River Birch
Betula nigra ‘Cully’
Twin groves of River Birch anchor two corners of Salesforce Park, softening the hard urban edges of the metal and glass skyscrapers that surround them. They’re among 600 trees and 16,000 plants that grow four stories above street level in a 4.5-acre park that spans four city blocks, perched atop San Francisco’s Salesforce Transit Center. The river birches are featured in The Wetland Garden, an area designed to “polish greywater and temporarily store, filter and clean runoff water” and to “provide habitat for butterflies, bees, birds and other creatures,” according to the park’s Garden Guide.
Heritage® Birch is the most widely planted of the River Birch cultivars, thanks to its lighter colored bark and large, glossy, light green leaves. Exfoliating bark of this bronze birch borer-resistant tree exposes mottled patches of cream, orange and pinkish tan colors. Mature height and spread are approximately 40’ x 30’. Widely adaptable, it performs well in California’s nearly frost-free Mediterranean climate and in much colder regions through USDA Zone 4.
Pyramidal European Hornbeam
Carpinus betulus ‘Fastigiata’
Columnar hornbeams line the curving pathway that circles the 4.5 acre rooftop park atop the Salesforce Transit Center. A stalwart performer on the street, this widely adaptable shade tree lends a formal look to boulevard and park plantings. Tightly columnar in youth, it widens with age to a height and width of 35’ x 25’. Symmetrical and formal in appearance, it is easily sheared and makes an excellent all-season screen, thanks to its dense, twiggy branch habit.
Heat and drought resistance, tolerance of urban air pollution, and adaptability to wet soils recommend Pyramidal Hornbeam for challenging planting sites. Shade tolerance makes it a good choice for urban canyons where the shadows of tall buildings limit direct sunlight. (NWST)
Landscape design by PWP Landscape Architecture, Berkeley, California, and landscape construction by McGuire and Hester, Alameda, California.
Bloodgood London Planetree
Platanus x acerifolia ‘Bloodgood’
In California, London Planetrees and native California sycamores are go-to solutions for tough urban settings. Here on Howard Street in the Yerba Buena district, these street trees form a cool, leafy tunnel that protects pedestrians and bicyclists from hot sun while producing oxygen and filtering harmful particulates from the air.
A popular tree for malls, parks, boulevards, parking lots and shopping centers, this big shade tree has stood the test of time and has become the standard against what other cultivars are judged. Introduced in 1900 by Meehan Nursery, Pennsylvania, it continues to be widely planted thanks to its ability to thrive in tough urban settings. Naturally shedding bark creates a dappled brown and cream pattern that accentuates sunlight filtering through the foliage. Notable for resistance to anthracnose, the cultivar grows in 30 years to a height and spread of approximately 50’ x 40’, and larger over its long lifespan. (Bare root, NWST)
