August 6th, 2015 by UWBG Horticulturist
If this year’s hot and dry summer is a climate change omen for Seattle and the greater PNW, then here’s the tree of our future: Lagerstroemia spp and its many hybrids and cultivars. Commonly known as crapemyrtles, these trees are tolerant of hot and dry summers and offer appeal throughout the seasons. They have lustrous foliage and large colorful flowers in the growing season (spring and summer); in the dormant season (fall and winter), the foliage and bark provide interest.
‘Sioux’ is a National Arboretum Fauriei Hybrid crapemyrtle introduction from the 1950s that produces an abundance of large, bright pink flower clusters during summer. Its foliage is the darkest green of any crapemyrtle and turns to a handsome purple color in fall. The bark is tan in color and the twigs have a reddish color. See National Arboretum link below for more information on the Fauriei hybrids.
Common Name: Sioux Crape Myrtle
Location: Center for Urban Horticulture, west end of Douglas Greenhouse parking lot
Origin: National Arboretum Introduction. Name registered May 1, 1992.
Height and Spread: 12′-15′ tall; 8′-10′ wide. Multi-stemmed small tree, large shrub
Bloom Time: Summer, extended out as long as temperatures remain warm.
Specimen at CUH
June 5th, 2015 by Jessica Farmer, Adult Education Supervisor
This small tree, commonly grown for its stunning reddish-brown bark, offers exceptional features throughout the year. Stewartia monadelpha, otherwise known as tall stewartia or orangebark stewartia, is just getting ready to come into bloom this month. Its white camellia-like flowers burst forth in early summer, followed by interesting brown seed pods and rich russet fall color. This species is planted in UW Botanic Gardens’ collections at both the Washington Park Arboretum and Center for Urban Horticulture.
Stewartia monadelpha is a member of the Camellia family. The small, white cup-shaped flowers last up to four weeks and have petals with smooth edges. This tree is best grown in partial shade but can handle full sun in the Pacific Northwest. It makes an excellent specimen tree for the home landscape.
Common Name: Tall Stewartia or Orangebark Stewartia
Location: Washington Park Arboretum: Camellia collection, Winter Garden; Center for Urban Horticulture: Event Lawn
Height and Spread: 20-25’ tall, 15-25’ wide
Bloom Time: June
Summer blooms of Stewartia monadelpha
Exfoliating bark of Stewartia monadelpha
Stewartia monadelpha fall color
Stewartia monadelpha in winter
March 23rd, 2015 by Soest Gardener, Riz Reyes
Wood Anemones are wonderful, easy to grow, spring ephemerals that require patience to get established, but once they get going, they form wonderful clumps in moist woodland conditions. What makes them sought after by gardeners is their ability to thrive in dry shade underneath mature trees. They have delicate fern-like foliage which set off the drifts of flowers that light up the spring landscape!
A. nemorosa flowers come in shades of blue, white, pink, with singles, doubles, and this most unusual form. This species has a remarkable tendency to mutate and the cultivar selection ‘Viridiflora’ (“green flower”) is a great example! What typically would be petals are actually modified leaves know as bracts. This creates an unusual moss-like texture and it’s absolutely charming combined with all the other plants in the garden as they burst into growth in spring. As with all wood anemones, they will begin to naturally die down in late spring and will rest until the following spring so be sure to mark where they are planted.
Genus species ‘Cultivar’: Anemone nemorosa ‘Viridiflora’
Common Name: Green flowered Wood Anemone
Location: CUH Soest Garden – Bed 7
Origin: Native to Europe, but selection may be of Garden Origin
Height and Spread: 4-5″ height x 24″ width spread on mature, undisturbed plantings
Bloom/Fruit Time: March-April
February 3rd, 2015 by Soest Gardener, Riz Reyes
Winter garden in the Pacific Northwest seems incomplete without this landscape standard. It has lush, glossy, evergreen foliage year round, takes dry shade conditions, and flowers in the wintertime with a powerful scent that perfumes the landscape. Sweet Box comes in two basic forms for the home gardener: the tall form and short form. The tall form (S. ruscifolia and S. confusa) get to about 2-3 feet in height and wide. The short form (varieties of S. hookeriana) makes somewhat of a groundcover with underground stolons that form a clump no taller than 12 inches and can spread about 3 feet.
In the garden, the ideal location for Sweet Box is under part shade with regular irrigation the first few seasons to get it established. It works well as a foundation planting up against the house and in mixed beds in a shaded woodland garden. Despite its common name and close relationship, Sweet Box can’t be treated like regular boxwood (Buxus sempervirens) and be sheared on a regular basis. To keep the size and shape in check, prune only the tall forms and prune shortly after they’ve finished blooming (March-April). This forces new growth and stems that will then flower the following winter. Pruning during the summer and fall will remove the new growth; therefore, the flower buds are sacrificed.
Sarcococca ruscifolia under an evergreen dogwood in the Fragrance Garden
Sarcococca hookerianna growing with Winter Daphne (Daphne odora ‘Aureomarginata’) for extreme fragrance
A close up of the flowers on S. ruscifolia
Common Name: Sweet Box
Location: Fragrance Garden
Origin: Eastern and Southeastern Asia, Himalayas
Height and Spread: Tall (2-3′ height x 3′ spread) – Short (1′ height x 3′ spread)
Bloom/Fruit Time: Late December-late February
December 31st, 2014 by Soest Gardener, Riz Reyes
The first of the year starts off with a bang with a most wonderful hellebore hybrid to ring in the new year showing the first blossoms of the season. Here at the Center for Urban Horticulture, we’ve acquired quite a selection of hellebores thanks to Skagit Gardens and Northwest Garden Nursery. ‘Shooting Star’ is one that’s been under our watchful eye for its third season now and we’ve been impressed with its excellent foliage and vigor along with the early flower power it possesses in the garden. We have it growing in three different locations at the Center for Urban Horticulture and each specimen is thriving, making it a stand-out in the winter landscape.
All types of hellebores are beginning to pop up at local nurseries. Many will be in full bloom, so you can select from hybrid seed strains or clones such as ‘Shooting Star,’ which will be all identical compared to the seed-grown strains. Hellebores make wonderful container plants and can be potted up or safely planted into the garden as long as the ground is not frozen.
‘Shooting Star’ opens to a pale blush pink with just a hint of green. As it ages, it slowly turns greener and the pink is accentuated. These “antiqued” blooms last into March.
Companions: Ophiopogon planiscapus ‘Nigrescens’ (black mondo grass), Cyclamen coum, Acorus gramineus ‘Ogon’ (sweet flag), Pulmonaria hyrbids (Lungwort)
Species: × ericsmithii
Cultivar: ‘Coseh 790’ Shooting Star USPP #22424
Common Name: Lenten Rose
Location: Douglas Parking Lot, Soest Garden South Slope, Miller Library North Foundation Plantings
Origin: Garden Origin
Height and Spread: 10-12 inches high and about 1.25 feet wide
Bloom/Fruit Time: Late December-early March
November 3rd, 2014 by Soest Gardener, Riz Reyes
Beautyberry is starting to put on quite a show and we have a species that isn’t common in Pacific Northwest Gardens. Callicarpa dichotoma is widely known on the East Coast and thrives in their summer heat and humidity. Having had an exceptionally lengthy summer here, our plants of ‘Early Amethyst’ look the best they’ve ever looked in the three years since they were planted out as small 1 gallon pots.
Combined with consistent moisture in full sun, they’re dripping in hot purple pink and look absolutely stunning in the autumn landscape! We hope the foliage has a chance to color up before a hard frost comes. Meanwhile, they are a sight to behold
Cultivar: ‘Early Amethyst’
Common Name: Beautyberry
Location: CUH Sidewalk Entry
Origin: China, Japan, Korea, Vietnam
Height and Spread: 4′ high x 4-5′ wide
Bloom/Fruit Time: September-frost
Growing with the bright gold, moisture loving Acorus gramineus ‘Ogon’
C. dichotoma ‘Early Amethyst’ with Persicaria amplexicaulis ‘Taurus’
October 1st, 2014 by Soest Gardener, Riz Reyes
A large indoor bulb that’s forced to flower in time for the holidays is often what gardeners think of when we say “Amaryllis.” Those large, almost dinner plate-sized flowers are actually the genus Hippeastrum. The true Amaryllis, depicted here, is a fall-blooming plant. Though its growth habit is similar to Hippeastrum, it can be grown outdoors in the Pacific Northwest
Native to South Africa, they thrive in Mediterranean type climates with full sun and well drained soil and are best left undisturbed once planted as they can take several years to flower from bulbs that are regularly available for planting in the spring.
Common Name: Naked Ladies
Location: McVay Courtyard
Origin: South Africa
Height and Spread: 15-18″ tall stems and forms clumps 3-5ft. in width over time
Bloom Time: August-October
July 1st, 2014 by Soest Gardener, Riz Reyes
Photo courtesy of Richie Steffen/Great Plant Picks
An evergreen hydrangea?!! You betcha!
There are very few evergreen vines for gardeners in the Pacific Northwest, but this gorgeous gem from Asia is becoming more readily available and it’s simply one of the coolest flowers you’ll ever get to witness opening.
From plump, peony-like buds, they begin to slowly crack open, a froth of fertile flowers begin to form and over the course of a few days, a flat umbel “lacecap” begins to form. People will begin to believe that it’s actually a hydrangea!
Hydrangea integrifolia is quite slow to establish (and re-establish, as we’ve learned after moving it to its new location at CUH three years ago) and may not even flower for the first few years of its life. Once it does, it puts on quite a show each summer. Dark green, glossy foliage remains year round. It’s a clinging plant that forms aerial roots on its stems. The aerial roots attach to a rough surface such as the bark of a tree or rough stucco wall; they don’t form tendrils or long whip-like shoots that wrap around supports so you have to carefully train them until they take hold. You could also let it sprawl on the ground as a ground-cover plant in a woodland garden.
They grow best in a protected spot in the garden such as a shady north-facing wall (such as our specimen here at the Center for Urban Horticulture), but they’re also quite at home tumbling over a stone wall in full sun with regular irrigation during the summer months.
Common Name: Evergreen Climbing Hydrangea
Location: Center for Urban Horticulture – Miller Library North Foundation Bed
Height and Spread: Can get 40′ tall and about 20′ wide
Bloom Time: Late June – July
May 6th, 2014 by Soest Gardener, Riz Reyes
Joseph Rock’s Peony has been prized by gardeners and avid collectors for decades. Botanist and plant explorer Joseph Rock earned the honor of having this exquisite flower named after him.
Peonies are divided into two basic types; the bush or herbaceous peony and the so-called tree peony. With similar flowers, the main difference between the two are their bloom times and their growth habit. Herbaceous peonies die back down to the ground each winter and bloom later in the season (May-June) whereas the tree peony, which isn’t really a tree, is more like a shrub with stems and branches that do not die back to the ground and flower mostly in May. Paeonia rockii is a tree peony.
Tree peonies are long-lived shrubs with exquisite flowers, but they take careful placement and a lot of patience until they’re well established.
They are best planted in the autumn so they are able to start forming new roots over the winter and it’s critical that they are planted in a location with full/part sun, well drained soil, good air circulation, and protected from strong winds that could damage the brittle branches. They can take several years to get established to consistently bloom each year and they also resent being transplanted.
Common Name: Joseph Rock’s Tree Peony
Location: Pacific Connections – China Entry
Origin: Gansu, China
Height and Spread: 6-8′ tall and about 5-7′ wide
Bloom/Fruit Time: Early-Mid May
A few selections of P. rockii can also be found growing at the Seattle Chinese Garden.
March 10th, 2014 by Soest Gardener, Riz Reyes
Photo by Mitch Evans
It may seem odd that we’re profiling a plant we currently don’t have yet at UWBG, but soon everyone will be able to see it in a very prominent spot at the Center for Urban Horticulture. After over 10 years in its place, the 2nd of two Parrotia persica (Persian Ironwood) in the Soest Garden will be removed to make room for a new tree that will take its place for the next 10 year cycle to cast part shade in Bed 2. Curation has selected the exquisite and rare Stewartia sinensis.
Many keen gardeners and horticulturists are familiar with the more common Stewartia pseudocamellia and the stunning bark of S. monodelpha. This Chinese stewartia seems to have been overlooked in the trade as descriptions state that the flowers are a hair smaller than that of S. pseudocamellia and monodelpha and the fact that it may be less hardy than the two species may also have contributed to its status as a collector’s item destined mainly for taxonomic collections. It has the same exquisite white blooms with the yellow stamens and the trunk of this small tree is truly exceptional with pretty peeling bark and a magnificent marbling pattern as the plant ages.
Be on the lookout for this stunning species. It will be years until it casts the kind of shade the underplantings of herbaceous perennials prefer, but the eventual effect will be quite dramatic.
Common Name: Chinese Stewartia
Location: Soest Garden Bed 2
Origin: Central China
Height and Spread: 20-25′ high x 15-20′ wide
Bloom/Fruit Time: June-July