Spring Pruning at the Arboretum

March 30th, 2011 by UWBG Arborist, Chris Watson

Recent Arboretum visitors may have noticed some unusual pruning, specifically in our Holly and Camellia collections.  The camellia specimens, located near the Lookout parking lot, will be re-propagated and planted in a different location to make space for the Pacific Connections New Zealand focal forest.  Large heading cuts were made to induce new epicormic growth, or watersprouts, which are ideal for propagation.  Cuttings for propagation will be taken later this summer.

The hollies can be found along the south side of Boyer Ave. near Lake Washington Blvd.  These hollies have been struggling since they were transplanted several years ago.  While not quite as radical as the camellia pruning, some might be surprised to see this style of pruning in the Arboretum, myself included!  However, in his book Hollies: The Genus Ilex, Fred Galle refers to a style of pruning called “hatracking or coatracking…best done in early spring, so new growth begins to cover the bare stems the first season…In two years the plants will show no signs of being severely pruned.”  We hope that this harsh pruning will induce a flush of new growth that rejuvenates these declining specimens.  Stay tuned for updates.

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Cherry Blossom Season is Here!

March 25th, 2011 by UWBG Horticulturist

Most visitors experiencing the beauty of our historic Azalea Way flowering cherries from now through May probably have no idea of how intensive maintaining their health and prolonging their longevity truly is for the UW Botanic Gardens horticulture staff.   Just ask our Integrated Pest manager, Ryan Garrison. Ryan with staff support spends many a day throughout the year monitoring and controlling the numerous diseases and insect pests our 175 plus cherries are prone to suffer from. Our rainy climate doesn’t help one bit either, especially when dealing with our most notable disease during blossom time;  a fungus known as Cherry Blossom Brown Rot. Yucko!  The good news is any new cherries we plant need to show a reasonable level of resistance. The not so good news is many of our older earlier bloomers, the ones extremely susceptible to the brown rot fungus,  need to be protected with fungicide applications during their bloom period.  As with all of our pest issues, we start with cultural and mechanical control efforts before resorting to chemical controls. The following Integrated Pest management (IPM) program discusses our best management practices for the control of blossom brown rot.  If you are interested in planting cherries for your home garden, I’ve included a list of cherries recommended for our PNW climate, all have good to excellent resistance to blossom brown rot.

Cherry Blossom Brown Rot - causal fungal agent known as Monolinia fructicola. The fungus overwinters on infected twigs and dried fruit on the tree or ground.  The fungal spores are spread in the spring by wind and rain through the blossoms, causing twig dieback.  As part of the UWBG IPM program, moving toward our goal of eliminating the use of all synthetic pesticides is our ultimate goal.

IPM relies on many strategies to manage plant health care. 

  • Proper ID of the pest and its life cycle
  • Regular monitoring of the plants
  • The use of physical, mechanical, cultural, and biological controls
  • Chemical controls used as a last resort*
  • Least toxic chemicals used

* All spray applications are in compliance with WSDA pesticide regulations.  Sign postings are located at all entrances and Graham Visitor Center. Spray applications are scheduled based on timing and weather. We do our best to apply when public are not present. For more information, pls contact, David Zuckerman at 206-543-8008 or dzman@uw.edu

The cherries are pruned in early fall  to remove infected twigs and improve air circulation.  Tree rings are given a fresh coat of mulch in the fall to bury any infected plant material that may be on the ground.  In our Cherry Replacement program we are only using cultivars that are resistant to Blossom Brown Rot.

Cherries recommended for the PNW:

    • Prunus ‘Berry Cascade Snow’
    • Prunus ‘Kwanzan’ syn. ‘Sekiyama’
    • Prunus ‘Pink Flair®’
    • Prunus ‘Royal Burgundy’
    • Prunus ‘Shirofugen’
    • Prunus ‘Shirotae’
    • Prunus ‘Snow Goose’
    • Prunus subhirtella var. ascendens
    • Prunus x yedoensis ‘Shidare Yoshino’

 

 

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Arboretum Foundation urges UW Interim President Wise to Maintain Washington Park Arboretum Funding

March 22nd, 2011 by Tech Librarian, Tracy Mehlin

Rhododendron hybrid by Ethan WeltyIn late February UW Interim President Phyllis Wise sent a report to the Washington State Legislature regarding potential budget cuts at UW specifically naming the Washington Park Arboretum. In response the Arboretum Foundation Board sent President Wise a letter urging her to maintain funding at current levels. Local writer Valerie Easton provides background information on this issue and contact details for state legislators. More from the Foundation.

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CUH Update – March 2011: Ramping up

March 21st, 2011 by Soest Gardener, Riz Reyes

Narcissus in Soest Garden

We all await the arrival of the most promising time of year as the garden slowly wakes up and showcases it early season splendor. March is when bulbs burst into bloom, spring ephemerals shyly shine and the winter shrubs are putting forth yet another splendid show of unrivaled color and, in most cases, outstanding fragrance.

Trillium chloropetalum in Bed 7 of the Soest Garden

Azara microphylla in full bloom scenting the Fragrance Garden with its chocolate/vanilla perfume.

It’s all  such a great distraction from  the financial woes and the economic downturn we’re all facing. Recent news of budget cuts and even threats to potentially eliminate the Arboretum from the University have caused us to be a little more on edge. Here’s a link to an article written by Valerie Easton on her blog about this situation. It’s really quite unsettling and as a gardener here, while we’re suppose to worry about a very busy spring season ahead, we’re all wondering if we’ll even have jobs come July. We’ve basically been learning to work with what little resources we’ve got and simply trying to stay motivated to get as much work done as possible.

Edmonds Community College students enjoy the sunshine as they install container plantings in the Soest Garden

Stepping back from our multiple tasks and looking out into the landscape, we’re simply in awe. This time of year has the potential to bring out the joy of what makes our profession so wonderful and unique. Bring out the sun and spirits are high!

We had the pleasure of hosting a group from Edmonds Community College’s Horticulture Department who dressed up some containers here at the Center for Urban Horticulture. In collaboration with garden designer, Wendy Welch and her fabulous container gardening class, we were treated with sunshine and an opportunity to see these young garden artists at work as they implement one of their designs as a series for our containers in the Soest Garden.

Here’s a note from Wendy about her student’s work:

“For their final project of the winter quarter Horticulture students from EDCC’s Container Gardening class designed and planted three containers in the courtyard at CUH. The long list of requirements for their designs included, a strong “winter picture”, at least one main element that is attractive year round, and at least two years of viability as a combination. All 22 students presented designs and then voted on the one they felt was the strongest. Jill Nunemaker’s design with Acer circinatum ‘Pacific Fire’, Sorbaria sorbifolia ‘Sem’, warm-colored cultivars of Heuchera and trailing Kininikinnick, won the vote by a landslide. Next years class will evaluated the success of these pots over time, as can all of you.”

Jill Nunemaker with her design, which includes a striking vine maple Acer circinatum 'Pacific Fire'

Seattle Garden Club also took part in a work party as members helped out in planting, transplanting and mulching within the Fragrance Garden. The site is now home to a few new plants with a few more still to come as we define the space a little more and more summer color will be more obvious with several perennials included this spring.

March is also the time we start to focus on WEEDS!!!! The gradual rise in temperatures and increased day length means the prolific germination of weed seeds that have been resting all winter. In a valiant effort in reducing our use and need for chemicals, we’ve been experimenting with various treatments such as torching (basically burning a plant with a flame) and a horticultural grade vinegar. We’ve seen signs of effectiveness, but we just need a few clearer and sunnier days to really see it take effect.

Anything we can do now to get on top of the big push of spring is crucial. With two gardeners left to oversee CUH grounds, it’ll be more challenging than ever, but everyone seems to be having patience and accepting the fact that some areas aren’t tended to right away, but for the most part, the gardens are looking great and visitors have been so pleased and enchanted by it all!

Chin up!

Riz

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Sonic Tomography at the Arboretum

March 18th, 2011 by UWBG Arborist, Chris Watson

The University of Washington Botanic Gardens would like to thank Tree Solutions, Inc. for bringing the latest technology in tree risk assessment to the Washington Park Arboretum.  Tree Solutions assessed a large western hemlock (Tsuga heterophylla) using sonic tomography, a device which measures sound waves to detect decay and other abnormalities in wood.

Assessing the risk associated with trees is a vital component to maintaining the urban forest.  Visually assessing a tree can often give more than enough information.  However, what cannot be seen can yield valuable information to the risk assessor or manager.

It is normal for trees that appear healthy to have decay inside the trunk and limbs.  It is the extent of this decay, along with the overall vitality of the tree that determines management (pruning, cabling, removal).  Traditional methods of assessing internal decay include sounding the tree with a mallet, increment borer, and drilling.  A more sophisticated method is the resistograph, which determines the decay extent using a very fine drill bit and produces a printed record.

Among the very latest technology is the minimally invasive procedure (i.e. no drilling!), sonic tomography.  Sound waves sent through the tree are measured by sensors placed around the assessed part, which feed into a computer.   The computer analyzes the input producing a color image which accurately shows healthy wood and decayed wood.  This detailed information greatly helps in determining management of the Arboretum main attraction…the trees!

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March Color Appears at the Washington Park Arboretum (Part II)

March 17th, 2011 by Pat Chinn-Sloan

Selected cuttings from the Washington Park Arboretum for the 2nd half of March 2011

  1. Buxus sempervirens ‘Belleville’ (Common Box)
  2. Corylus avellana ‘Contorta’ (Harry Lauder’s Walking Stick)
  3. Photinia davidiana var. davidiana
  4. Ribes sanguineum ‘Henry Henneman’
  5. X Sycoparrotia semidecidua

Complete details.

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Over 100 New Accessions Added in 2010

March 15th, 2011 by Tech Librarian, Tracy Mehlin

UW Botanic Gardens Collection Manager, Randall Hitchin, reported that the majority of new plants added in 2010 represent plants that have never grown at the Arboretum before and one-third of specimens grew from wild collected seeds. The annual Curatorial Report for 2010 gives a summary of the plant collection statistics, including the total number of specimens and number of plant families represented. The full report is linked below.

UWBG Curatorial Report 2010

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Hollies in Good Condition After Relocation

March 15th, 2011 by Tech Librarian, Tracy Mehlin
Ilex opaca in WPAA mature Ilex opaca tree that stayed behind in the Pacific Connections Garden 

UW Botanic Gardens Collection Manager, Randall Hitchin, reports the majority of the hollies transplanted in 1999 are in good or excellent condition. More than 150 plants were moved in order to make room for the new Pacific Connection Garden.

The Arboretum has one of the most diverse holly collections in the United States. The collection grows on the west side of Lake Washington Blvd just south of Boyer Ave.

2010 Holly Collection Summary for the Washington Park Arboretum

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March 2011 Plant Profile: The Genus Helleborus

March 9th, 2011 by Soest Gardener, Riz Reyes

The popularity of this tough and resilient perennial has made it one of the most revered and sought after of all winter blooming plants in our climate. The range of varieties and different color forms now available is quite remarkable and being able to select just one for your garden is near impossible.

Helleborus x hybridus Winter Jewels™ Black Diamond

By far the most popular and well known are the diverse hybrids of Helleborus x hybridus (often incorrectly dubbed as Helleborus orientalis) or the Lenten Rose. These represent the wide range of colors and forms that currently exist and some of the finest examples come from a breeder who generously donated some of their previous breeding stock to UW Botanic Gardens, which are all now in full bloom at the Center for Urban Horticulture. Ernie and Marietta O’byrne of Northwest Garden Nursery developed the fabulous Winter Jewels Series. Thousands of crosses comprised of hybrids bred from at least 16 different species make up several color strains to showcase much improved flower forms, exquisite colors and unusual markings.

Here’s just an example of their work and what’s currently blooming now:

Helleborus x hybridus Winter Jewels™ Jade Star flower reverse

Helleborus x hybridus Winter Jewels™ Onyx Odyssey reverse

Helleborus Winter Jewels™ Painted

Helleborus x hybridus Winter Jewels™ Golden Lotus

When it comes to early bloom, prolific flowers and sturdy, disease-free foliage, the new hybrids coming out of Europe are tough to beat. The “Gold Collection”, again a complex series of hybrids are actually identical clones propagated vegetatively (via tissue culture) to ensure uniformity. In varying shades of pure white, cream, to deep saturated pinks, these have proven to be vigorous and excellent garden or container perennials. ‘Joseph Lemper’ our January 2010 Plant Profile) along with ‘Jacob’ are two selections of Helleborus niger that are a part of this Gold Collection. Then you have the exquisite quality of varieties such as ‘Ivory Prince’ and ‘Pink Frost’ that are flying off the nursery tables at nurseries in mid-winter.

Helleborus 'Josef Lemper'

A brand new hybrid that was new for us last year is getting established and looking quite lovely is Helleborus x ‘Rosemary’. An unusual cross between H x hybridus and H. niger bringout the fine qualities of both plants.

Then you have the sturdiness and dependability of species such as Helleborus argutifolius, the Corsican Hellebore, which opens later in the spring with pale green flowers. A selection called ‘Silver Lace’ is lovely with finer dissected foliage and a more compact habit. Helleborus foetidus you can find growing in the Fragrance Garden despite its unpleasant smell if admired up close, The foliage is exquisitely elegant, narrow and finely dissected.

Hellebores will be the highlight of an early spring plant sale taking place here at CUH being run by the Northwest Horticultural Society. Proceeds from the sales go to support the Miller Horticultural Library and there will be plant vendors from all around the Puget Sound region selling plants and, yes, they’ve been asked to also bring their blooming hellebores to entice you! There will be demonstrations, displays, and even a talk by renowned plantsman, Dan Hinkley.

For more information, please visit our page dedicated to this event!

This is the perfect month to see these wonderful jewels in person as the weather begins to warm, the earliest of bulbs begin to pop and the color heralding the arrival of spring.

Common Name: Lenten Rose, Christmas Rose
Family: Ranunculaceae
Location: Throughout CUH
Origin: Original species come from Eastern regions of Europe. Mostly hybrids.
Height: 10″-18″ tall
Spread: mature clumps can get 2.5ft. wide
Bloom Time: Mid-Winter-Early Spring
Bloom Type/Color: Flowers composed of persistent sepals often marked or fully double with central nectaries. Flowers are out to downfacing opening sequentially.
Water/Soil: Moist to moderately dry. Drought tolerant once established.

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2011 Urban Forest Symposium

March 8th, 2011 by Tech Librarian, Tracy Mehlin

Arboretum Drive by E. WeltyTrees and the Urban Infrastructure

Plant Amnesty and the University of Washington Botanic Gardens are reprising their highly successful Urban Forestry Symposium, an all day event at the Center for Urban Horticulture. The past two symposiums have focused on the value and preservation of trees; this year’s event will delve into the nitty gritty of how can trees and urban infrastructure co-exist. The event will bring together highly-regarded “tree people” from a variety of fields that affect urban trees, including ecologists, arborists, landscape architects, and utility planners. The symposium promises to be highly informative, with sessions covering topics ranging from foundational values to technical solutions and political strategies. Inspirational keynote speaker Chris Maser has been called “Gandhi of the forest”. He is a research ecologist and courageous writer who rethinks the future beyond simple slogans – using hard science and the wisdom of the ages he can and will show us how the urban forest can be designed to effectively serve the citizens of the city. Additional presentations and panels promise to be lively.

Where:                UWBG Center for Urban Horticulture, 3501 NE 41st Street, Seattle 98105

When:                  Monday, May 9, 2011 from 9 am to 4 pm

Cost:                      $55.   Lunch is an additional $15.  Bringing your own sack lunch is also an                                     option.  There will be a free lunch for the first 50 registrants.

Credits:                Credits available for ISA, WALP, WSNLA, APLD WA and ASLA members.

Contact:               Jean Robins at 206-685-8033, jrobins@uw.edu

Complete informationRegister online or print and return this registration form.

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