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
May 6th, 2015 by Soest Gardener, Riz Reyes
The peony has been a staple in gardens for hundreds of years and the UW Botanic Gardens has a wonderful representation of the genus this month at both the Washington Park Arboretum (WPA) and the Center for Urban Horticulture (CUH).
This month we are highlighting a spectacular peony that’s currently in bloom in the Pacific Connections Entry Gateway. Visitors stopped in their tracks by the large, dinner plate-sized blooms which emit a wonderful scent. This is a pink form of the typically white flowered P. rockii. Found in Northwest China in Gansu Province. This species is characterized by a deep purple pattern in the center of each petal.
This type of peony is referred to as a “Tree Peony” by most gardeners. Although it’s not technically a tree, it is a woody shrub that does not die back and should not be cut down in the autumn like the more common bush peonies many people know. But like the bush form, it takes a few years before the plant is established and starts blooming well.
Both types are generally planted in the fall, but potted plants can be purchased and planted just about any time of year (except when the ground is frozen).
Genus species: Paeonia suffruticosa subsp. rockii
Common Name: Rock’s Peony, Joseph Rock Peony, Ziban Mudan
Location: WPA – Pacific Connections – China Entry Garden
Origin: NW China, Gansu Province
Height and Spread: 5-7′ height x 6′ width spread on mature, undisturbed plantings
Bloom/Fruit Time: April-May
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
March 3rd, 2015 by Soest Gardener, Riz Reyes
The manzanita is one of the most iconic of all West Coast native trees and shrubs, yet they are rarely ever seen in gardens. Like their famous relative, Arbutus menziesii (The Pacific Madrone), they’ve earned a reputation of being slow and difficult to establish. But with a strong emphasis in introducing more of our native flora into our gardens and the constant demand for drought tolerant plantings, the wide range of Manzanita species and hybrids have really started to come to the fore and gardeners are rediscovering their unique and stately presence in the landscape.
We have several specimens slowly getting established the Center for Urban Horticulture’s McVay Courtyard and one of the standouts is A. densiflora ‘Sentinel’. An upright grower discovered in Sonoma County, CA, it is one of the faster growing selections and it is also one of the most adaptable of the genus. The clusters of pink-to-white, urn-shaped flowers appear in later winter into spring like many in the genus, but the year round attraction is the evergreen foliage and the smooth and dramatic trunks with the often peeling, russet red bark. The older the specimen, the better they become.
Manzanitas require full open sun and very well drained soil that’s relatively lean. Avoid adding too much organic material to your soil and though they are drought tolerant, regular irrigation and fertilizer the first 2-3 years will get them going. They highly resent heavy root disturbance so take care when planting and avoid having to transplant it once its established in the ground. Staking of younger plants during planting is beneficial until they fully root in and settle.
Genus species ‘Cultivar’: Arctostaphylos densiflora ‘Sentinel’
Common Name: Sentinel Manzanita
Location: McVay Courtyard – CUH
Origin: CA, USA
Height and Spread: 4-6′ height x 6′ wide
Bloom/Fruit Time: Late February-March
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
December 1st, 2014 by Soest Gardener, Riz Reyes
Looking nondescript throughout most of the year, the so-called “Christmas cactus” puts on a tremendous show as the holidays arrive in November and December.
As part of the Cactus family, they are actually epipthytic plants (similar to air plants) that grow on rock crevices and trees in the wild and require a well drained potting mixture and specific dry rest periods in order to initiate flowering when grown as a house plant.
Most receive a Christmas cactus as a blooming gift for the holidays. They can be enjoyed anywhere in the home where it receives bright, indirect lighting, humidity and very sparse (about once every two weeks) watering. Following the tremendous floral show, plants will rest and watering is greatly reduced further until about March or April when they can be re-potted if desired (although they prefer the tight confines of being potbound in a small container). New growth resumes and regular watering and fertilizing (all purpose fertilizer is fine) can take place (once every week or two). They can also sit outdoors up against the house protected from direct light during the summer and can be treated like other container plants.
To initiate flowering again:
Water is withheld as days get shorter and temperatures begin to drop. They need a cycle of normal daylight and then complete darkness for 12-14 hours for about 6 weeks. All this usually begins around September into October where you can either start bringing them indoors in a room that will be completely dark for that period of time or they can stay outdoors and make sure street lights aren’t disrupting this dry/dark period. If temperatures are expected to drop below 55F, then the plants should be brought inside.
After this treatment, buds should have formed and regular watering and care (once every one or two weeks) can resume as they begin to open and flower.
A bright, deep pink Schlumbergera begins to show off amongst the tropicals just as you enter the Douglas Conservatory.
species: × buckleyi (T.Moore) Tjaden = S. russelliana × S. truncata; S. Buckleyi Group is the most common.
Cultivar: Assorted named cultivars exist, but often offered by color only
Common Name: Thanksgiving/Christmas Cactus, Zygo-Cactus
Location: CUH Douglas Conservatory Entry
Origin: Wild species originate from SE Brazil
Height and Spread: 1.5-2′ high with stems that can drape 3-4ft. long
Bloom/Fruit Time: November-early January
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