Restoration and Renewal in the Goodfellow Grove

May 11th, 2015 by Rosemary Baker

Salmonberry (Rubus spectabilis) and white western redbud (Cercis occidentalis alba) in April bloom

It’s spring and time for a full on revival in the Center for Urban Horticulture’s Goodfellow Grove!  Dedicated to the late Marilou Goodfellow, the Grove was designed to demonstrate the use of native plants in a transitional landscape and is aptly located between the formal ornamental gardens in and around the Center for Urban Horticulture and the “wilderness” of the Union Bay Natural Area.

As a former UW Botanic Gardens graduate student, a botanist and restoration ecologist, and landscape designer specializing in native plants with horticultural appeal, I am thankful for the opportunity as the new gardener assigned to the grove.

We are working on re-defining original beds and pathways, taming and radically renovating shrubs and trees, and will be installing beautiful true native/native cultivar wildflowers and groundcovers for the upcoming summer events season.  If you see me, ask me about wild foraging – there are some native edibles in the grove and even the weeds are delicious…








The serviceberry grove (Amelanchier x grandiflora) in full April


Cardamine oligosperma also known as bittercress or shot-weed is an edible green great for mixed salads

Weeding Strategies from a Professional

May 4th, 2015 by UWBG Communication Staff

Photo by vilseskogen

April showers bring May weeds? Shotweed, dandelion, buttercup, morning glory and SO MANY MORE weeds thrive in our mild maritime climate. Many home gardeners feel overwhelmed by unwanted plants crowding out desirable flowers or vegetables.  How do professional gardeners manage weeds? Kathleen DeMaria, Botanic Gardens  Horticulturist, shares her favorite tool and the strategy she uses in the New Zealand forest at the Washington Park Arboretum.

“If I could only have one gardening tool for the rest of my life it would be a digging fork with a ‘D’ handle. Not a curved fork like a pitchfork, but a smaller fork with four flat, thick, stainless steel tines. I prefer the D handle over the T handle because I feel I get more leverage with it and feels right with my wrist. I use it to loosen soil around an area before I weed or to turn over soil and break up heavy clumps. It is also great for getting to the base of a dandelion without snapping it or cutting it.”

“As far as philosophy and  technique, I like to use my fork to loosen an entire area and then use my hori hori to help me pull the weeds without leaving the roots in the soil. I tend to work on clearing one area at a time and then mulch the area right after I weed it to give me some extra time before the weeds come back. In spring I’m less systematic and go into triage mode and seek and destroy anything that is close to seeding or fully engulfing another plant.”

Exploding trees, now showing at your local Arboretum

April 1st, 2015 by Kathleen DeMaria, Arboretum Gardener

March did not go out like a lamb, nor did it end with a whimper. No, this lion ended with a grand BANG!

A lightning strike from the massive thunderstorm that roared through Seattle yesterday was a direct hit on one of our largest trees in the Washington Park Arboretum.

Lighting strike as seen from the Columbia Tower. Photo courtesy of KOMO

Lighting strike as seen from a helicopter and from the Columbia Tower. Photos courtesy of KOMO


A Grand Fir located in the Oak grove at the north end of the Arboretum was obliterated with one flash. All that remains of a tree that was easily over 100 feet tall is a jagged snag and a circular field of debris extending at least 150 feet in all directions.

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Electricity always takes the path of least resistance, so arborists in places where lightning is common will install tree protection systems. These usually are metal rods affixed to the top of the tree with a metal cable running down the tree to a ground rod buried deep in the soil. This system allows the tree to avoid catastrophic explosions like the one we had yesterday. Lightning is relatively uncommon in the Seattle area, so none of our trees have lightning protection systems.

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So why did the tree explode instead of just breaking or cracking? Good question. A lightning bolt is hotter than the surface of the sun and has a strong electric current. The current is carried through the tree by the sapwood below the bark. This sapwood is composed of mostly water and when the bolt’s heat and electrical charge hit the tree, the water boils instantly and turns to steam; just like a pressure cooker, except the tree doesn’t have a steam release valve on top. So the result of the excessive heat and  pressure causes the tree to explode. This is not common, but the results are spectacular!

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We will never know why this tree was hit, but we have had a day full of speculation and mitigating safety hazards. Was the lightning attracted to this metal bolt inside the tree from a former cable?

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Was it just a case of being in the wrong place at the wrong time? Was it the high volume of spring sap running? Was it because it was the tallest tree in an open area near water? Was it all of these factors and some unknown? We may never know but we will never forget.

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One odd bonus of this amazing event is that lightning strikes are one of a few (non-synthetic) ways to fix nitrogen in the soil. Along with nitrogen-fixing bacteria and algae, the heat of a lightning flash causes atmospheric nitrogen to combine with oxygen to form nitrogen oxides. These oxides then combine with atmospheric moisture and are then delivered to the soil by rain, where it is transformed by microorganisms into nitrates that can be taken up by plant roots. Fascinating.

We know you never need an excuse to visit the Washington Park Arboretum, but we plan to keep the debris field intact for a few more days so any curious onlookers can come and check out our exploding tree. For your own safety, please stay behind the barriers, and enjoy the show.




Fragrance Garden renovation enters phase two

December 3rd, 2014 by UWBG Communication Staff

The Fragrance Garden at the Center for Urban Horticulture is being refreshed with help from partner the Seattle Garden Club. The declining stripe bark maple will be removed and new scented plants will be added.

Fragrance Garden at CUH 11-2014Manager of Horticulture David Zuckerman said the Acer capillipes has been declining for years. David explained: “it may have verticillium wilt, but more likely to be causing the decline are symptoms of over exposure (sun, temps) during the course of its life in the entry garden. In general, stripe bark maples are forest edge trees, somewhat short lived and do not do well when grown in exposed conditions.”

A few of the new plants going in include:

  • Magnolia virginiana ‘Moonglow’
  • Itoh peonies
  • Berberis x media ‘Winter Sun’
  • Philadelphus ‘Belle Etoile’
  • Azara microphylla
  • Pieris japonica ‘Cavatine’
  • Chimonanthus praecox

Arboretum Loop Trail nears construction start

November 5th, 2014 by UWBG Communication Staff

By Audrey Wennblom

An artist's rendering of one of the bridges on the Arboretum Loop Trail. Image courtesy the Berger Partnership

An artist’s rendering of one of the bridges on the Arboretum Loop Trail. Image courtesy the Berger Partnership

At long last, the Arboretum Loop Trail (ALT) appears to be just a few months away from the start of construction. “Right now, it looks like the tentative start date would be late spring 2015,” said Raymond J. Larson, Curator of Living Collections for the UW Botanic Gardens. “The idea is to start after most of the rain has passed and to do construction over the drier months.’’

Depending on the the bids received, Larson said the project may be done in two phases. The first phase would be from E. Madison Street to the Boyer/Birch parking lot along E. Lake Washington Blvd. (across from the Holly Collection), he said. The second phase, in 2016, would be from the Birch Lot to the Graham Visitors Center. Larson said, however, that it could also happen all at once. “It depends on a variety of factors,” he said, “and the contractor selected.”

But before any work begins, “the first thing we will do in the field is contract out the transplanting of collections,” said David Zuckerman, Horticulture Manager for the UWBG. “This work will begin as early as this fall sometime, even if it’s just root pruning,” he said.

The ALT is expected to have several benefits for the Arboretum.  “First, it will get people into areas of the arboretum that are currently less well known and visited,” Larson said.  Most people don’t make it to the viburnum collection or know where it is, and don’t get through the Flats (where birches, poplars and the creek is) much of the year because the ground is too wet and there are no trails there, Larson said.  “The ALT will also open up a new route through the largely undeveloped southern hillside across from the Japanese Garden and will provide another way to access the Pacific Connections Gardens,” said Larson.  That is an area currently difficult to navigate and where it is easy to get disoriented (especially for new or occasional visitors), Larson said. Access is going to be much better and the park should feel bigger, he said.

The collections themselves will also benefit. “We will have many new planting areas that will be accessible and viewable,” Larson said.  Some of these will anticipate future phases of the Pacific Connections China and Chile ecogeographic gardens.  “Where the trail crosses through these areas we will be planting plants from those areas along the way,” Larson said.  Other areas will see the addition of a diversity of new plantings that strengthen existing collections (viburnums, oaks, rhododendrons, etc.). “There are going to be a lot of new plants going in, and areas with a lot of ivy and invasives will be refreshed,” he said.

All of this adds up to a better visitor experience—finding your way more clearly as you navigate through the gardens. The north end will be enhanced with better sightlines and a clearer, more obvious connection to the Graham Visitors Center, where the trail forms a loop with Arboretum Drive E, Larson said.  It should feel less hidden and more welcoming.  Some existing blind spots will be improved and in general areas should feel refreshed.  “We think this will be a popular walking and bicycling trail, and the loop connection should help people better experience more of the park,” Larson said.

More Information

Seattle Department of Planning and Development trail project page

Seattle Parks and Recreation trail project page

What to do with fallen leaves? Arborist Chris Watson considers the options

November 2nd, 2014 by UWBG Communication Staff

Beautiful fallen leaves from the Amelanchiers growing at the Center for Urban Horticulture. Photo by Larry Howard 2007

To rake or not to rake? When asked what homeowners should do with leaves falling from trees growing in city gardens, Chris Watson, the Arborist who cares for the trees at the Washington Park Arboretum definitively stated, “It depends!”

Is the best mulch for a tree its own leaves? Or does that spread disease and pests? Chris explained:

“From a nutrient cycling perspective, ideally the leaves would be left in place where they fall.  Much like a forest, this would reduce the need for additional inputs, such as fertilizer. However, the urban situation is quite different from a forest.  We have introduced plants, soils, pests and diseases, as well as the desire for aesthetically pleasing landscapes.  Leaves blow in the wind and have the potential to clog drains.  Also, the first best management practice for most foliar diseases is to remove all leaves when they fall to reduce inoculum.

“When leaf removal is necessary, I recommend composting leaf material if possible.  The compost can then be used to amend soils around landscape plants.  If leaves are diseased, they should be composted in a way that increases the temperature to sterilize pathogens.  This is difficult to do for the typical homeowner, so it may be best to place leaves in the yard waste bin where they will be processed in a suitable manner.”

Winter Garden Project: Remodeling the “Living Walls”

August 20th, 2014 by UWBG Horticulturist

Arboretum Tree Removal Notification:


The week of 8/25/14, UWBG tree crew will embark on a project located in the Winter Garden (read about project below). 

4 western red cedars will be removed due to negative impact to plant collections and garden encroachment. 

All pedestrian path detours and other safety considerations will be handled by tree crew. 

If possible, cedar logs will be salvaged for future park uses.  

UW professor of landscape architecture and designer of our Winter Garden (1987), Iain Robertson, states it’s time to open up the “room” that has been closing in on the Winter Garden for over 25 years. Continuous growth of the “living walls”, predominantly western red cedars, is now negatively impacting many of the garden’s choice plant collections. Due to this encroachment, the garden “room” is feeling confining. Judicious consideration and deliberation has led to the following curation and horticultural decisions.

Project Scope:

  • Removal of 4 western red cedars to provide needed light and future growing space for plant collections. In all cases, the “room’s walls” will expand, yet filled in by existing trees in the background to continue to provide the experience of being in an enclosed space.Pruning of several other cedars to provide light and future growing space for plant collections.
    • 2 on the west side in the “twig bed”
    • 1 on the south side next to the Chinese red birch grove
    • 1 on the east side growing over several camellias and other collections

The “Lost” Enkianthus Grove in Washington Park Arboretum

August 8th, 2014 by UWBG Horticulturist

Does anyone reading this know where our arboretum’s “lost” Enkianthus grove is located? By “lost”, I mean extremely well-hidden under a dense canopy of western red cedars and other trees.


Enkianthus specimens previously “lost” in the overgrowth.

Enkianthus are shade-tolerant shrubs, but NOT “black-hole” shade tolerant. Like most living plants, they do need light to grow and thrive.  It’s a bit embarrassing, but I can honestly say, during my 30 plus year tenure on the UWBG horticulture staff, I don’t recall ever working in the area for longer than maybe a day cleaning up after a storm or pruning a few of the bigger trees. And, we definitely did not pay any attention to the main attraction – a grove of over 50 Enkianthus specimens, mostly all E. campanulatus (red-vein enkianthus) and over 70 years old! Well, the answer to the question above is Rhododendron Glen, encompassing several grid maps (14-2E, 14-3E and 15-3E).


Accession number 2352-37, this Enkianthus campanulatus was planted in 1937.

Now for the good news. Thanks to funding designated for Rhododendron Glen, our horticulture staff has taken on the project to restore the grove for all to be able to once again, after a very long hiatus, enjoy its natural beauty and splendor throughout the year.

The project scope includes the following to improve the health and display of the Enkianthus grove:

  • Increase light conditions through selective understory brush clearing, tree removals and pruning
  • Open view corridors and a cleared natural pathway for visitors to walk from the upper Rhododendron Glen pond area down to the lower “Lookout” pond
  • Improve health of the Enkianthus through practicing sound horticulture: mulching, watering and fertilizing the grove

For more information about the ornamental shrub, Enkianthus campanulatus, go to Wikipedia website below:





Harbinger of Spring in Seattle – Flowering cherries on Azalea Way!

March 20th, 2014 by UWBG Horticulturist

Cherry photoMost 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.

14 new cherries will be planted along Azalea Way, Spring of 2014! Thanks to the UW being awarded funds from the Nationwide Cherry Blossom Tree Planting Initiative grant co-sponsored by the Consulate-General of Japan in Seattle and other supporting local community organizations.

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

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’

Coming Attractions for 2014 in Horticulture and Plant Records

January 21st, 2014 by UWBG Horticulturist

There is much to look forward to in 2014 for the University of Washington Botanic Gardens (UWBG) horticulture and plant records staff. It will be a rare year of “normality” between capital project implementations, the completed 2013 Pacific Connections Gardens (PCG) New Zealand (NZ) forest exhibit and the looming 2015 multi-use trail. Our resources will be focused on smaller scale deferred maintenance projects of several gardens and plant collections, catching up with plant labeling and mapping of our Pacific Connections Gardens and embarking on a few recently awarded grants.

Washington Park Arboretum (WPA)

On the grants front, this spring, Azalea Way and the Japanese Garden will be receiving new cherry trees, along with funding to support future maintenance, thanks to the Japanese Embassy’s Nationwide Cherry Blossom Planting Initiative. Fourteen cherries will be installed of various types, ranging from the tide-and-true classical hybrids to the newer, disease-resistant cultivars. We hope to tap into the services of our volunteer Azalea Way stewards force to help in their planting, establishment and future care.

Club Car vs JD Gator

Club Car vs JD Gator

We just heard that we were awarded $33 thousand from the UW Green Seeds funds, a grants program that engages our UW community in sustainability research that will have a direct affect on reducing UW campus’ carbon footprint. Our 1 year study will allow us to purchase 2  new utility vehicles, 1 electric and 1 bio-diesel, which will be the test subjects of a research project titled:  “Grounds Utility Vehicle Carbon Footprint Comparison Study”. Results and conclusions will be disseminated at the end of the study to UW Grounds Management, Seattle City Parks and Recreation, and other local municipalities and private organizations that employ utility vehicles to perform grounds maintenance tasks.

Our curator, Ray Larson, is busy developing plant lists and procuring new plants for refreshing and embellishing many plant collections displays and exhibits. Our horticulturists will be installing exciting new cultivars and hybrids in the PCG entry gardens of Australia, Cascadia and China.  Also, wild-collected specimens from our container nursery inventory will be planted out in the future China forest portion which was cleared during the NZ forest construction last year. We hope to receive several tree peony cultivars from the Seattle Chinese garden. The  American Peony Arts and Cultural Association is promoting Luoyang peonies. These donations may be planted in the PCG China entry garden, in our original peony display along Arboretum Drive and/or over at the Center for Urban Horticulture.

Overgrown Camellias ready for renovating!

Overgrown Camellias ready for renovating!

Other gardens and collections of 2014 focus for small-scale renovations and/or new plantings include the Winter Garden, Camellias, Hollies, Maples, Pinetum and Viburnums.

On the Plant Records front, catching up with our backlog of labeling and mapping will be a major goal for all UWBG gardens and collections, specifically PCG’s NZ forest and Chilean Gateway. Mapping our collections has moved into the 21st century using sophisticated survey equipment to gather Geo-referenced points that will enable all sorts of modern applications for staff and public alike who want more information on the locations and data of our plant collections.

Center for Urban Horticulture (CUH)

The horticulturists at CUH will certainly not be any less busy or ambitious  in 2014 than those at WPA. The following projects are either underway or in the works:

  •  New plantings for the McVay stairs will include a new bench, bringing back the solar fountain from WPA and, if room allows, also incorporating a container or two.
  • Our “face” along 41st Street is undergoing a much needed “lift.” After the new fence is built, there will be opportunities for new plantings along it. Also, expect to finally see our “Welcome” signs get installed onto the long awaiting stands at both ends of our frontage.
  • Speaking of signs, the tired-looking interpretive signs in the Orin & Althea Soest Herbaceous Display Garden will be replaced shortly. Also, keep your eyes open for changes and new plantings in a few of the Soest display beds.
  • If funding comes through, the Fragrance Garden bed along NHS Hall is on the schedule for renovation this year as well.
  • Goodfellow Grove will continue to be a focus of renovation, with considerable restorative pruning and thinning beds, path and lawn improvements.
  • Later this year, clearing of vegetation around Central pond in the Union Bay Natural Area will take place in hopes of providing more habitat for shore-birds and increasing their diversity.
Solar Fountain to return to CUH

Solar Fountain to return to CUH

As you can see, there’s plenty of work to be done by the UWBG horticulture and plant records staff in 2014. And, yes, a sigh of relief to be able to broaden our horizons beyond all-consuming capital projects for the year to focus on these smaller maintenance improvements of our established gardens, grounds  and collections.  Please stay tuned for further posts and photos on many of these exciting changes to take place in 2014 at our botanic gardens.