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


Winter Plant Protection in Pacific Connections Gardens

November 22nd, 2010 by UWBG Horticulturist

"Straw Tepees" in New Zealand entry garden

No, aliens haven’t invaded the arboretum. The “straw tepees” (left), as Kyle Henegar, PCG gardener, aptly coins them, are to protect the newly planted Phormiums and other marginally hardy New Zealand plants make it through this cold spell that’s hit Seattle. It just wouldn’t seem fair to let these plants try to make it on their own since they were just planted late last summer and have yet to get their roots established.

The new Chilean Gateway garden also has several box structures dotted along the rockery hillside (bottom right). These wooden frames enveloped w/ shade cloth are protecting our new Chilean wine palms that are indeed cold sensitive.

Box over palm

Sundstrom, Gateway contractor, has also treated the palm’s crowns w/ a copper-based pesticide, to help inhibit the colonization of bacteria and fungal crown rots. If you look inside the structures, you’ll notice straw has been used to blanket the trunks and crowns as well.

Let’s all hope that these extraordinary winter protection measures pay off. We won’t know for sure until late spring or even early summer in some cases. And no, you needn’t worry about alien invasions in the arboretum.


Cherry Pruning Time

October 8th, 2010 by UWBG Horticulturist

Our horticulture staff will begin pruning our cherry collection, mostly along Azalea Way, next week. October is our window to prune based on the life-cycle of the insect pest, Cherry Bark Tortrix -it’s not flying around seeking easy entry portals like fresh pruning wounds now. Most of our pruning focuses on  large dead branches, as well as, unwanted basal suckers below graft unions. We just don’t have the staff to detail out all the small dead twiggy growth from years of brown rot infestations. We do mulch our cherries which helps decrease amount of fungal spores to reinfect next year’s blossoms.

Also, our tree crew will be removing 7 decrepit – brown rot and decay riddled, poor health specimens. 6 are Prunus subhirtella cvs. (the most susceptible to brown rot) and one is a Prunus sargentii w/ significant crown die-back. We may decide to replant if the sites are suitable w/ brown rot resistant cultivars in the future.


Garden Loosestrife – Spray Application Scheduled 9/22

September 14th, 2010 by UWBG Horticulturist

UWBG IPM staff will be out on Union Bay, Wednesday, September 22nd, w/ spray contractor NW Aquatic Eco-Systems. All canoe landings and shoreline trailheads will be posted. This is the second of  two  follow-up spray applications in our effort to control the class A noxious weed, Garden Loosestrife.


Holly Garden Project Notice and News

August 26th, 2010 by UWBG Horticulturist

Eurasian berms are located at far right - in pink


September through October is our window of opportunity before fall rains begin to commence development and improvement work in the Holly collection.  Scope of work during this period will focus primarily on construction  of  the southernmost Eurasian clade berm located at the north end (near Boyer Ave). See photo of Iain Robertson’s conceptual Holly collection plan – Eurasian clade berms are pink. 

  • In-house tree removals  – 4 small undesirable Bigleaf maples and 4 maple stump sprouts
  • Contract tree removals  – 6 cottonwoods and 1 Western red cedar
  • Also, removal of 4 collection hollies in very poor condition in existing Eurasian berms

During this project work, area will be cordoned off to public and if needed, pedestrian detours will be established. 

Project info will be posted at work site and at the Graham Visitors Center. 

Beginning in late October 2010, regional Qwest corp, will begin a new partnership with UW Botanic Gardens and Seattle City Parks and Recreation. Under the guidance and training of UWBG horticulture staff, Qwest  volunteers, known as Pioneers, will ultimately “adopt” the Holly garden for a year in all facets of horticulture care and maintenance. Initial tasks will focus on: 

  • Finishing southernmost Eurasian clade berm construction if weather permits – grubbing, grading, soil work
  • Modification of northernmost Eurasian clade berm – adding more soil to raise profile and improve drainage
  • Plant and care of several new holly collections, mostly Eurasian clade members
  • General maintenance (weeding, mulching and edging) of the entire Holly garden, including native restoration sites

We look forward to our new partnership with Qwest Pioneers and a marked improvement of our Holly garden.A project sign will be installed on-site in the next few weeks by Seattle City Parks and Recreation.


Garden Loosestrife Spray Scheduled – Wed., August 18, 2010

August 13th, 2010 by UWBG Horticulturist

Garden Loosestrife (GL) control contractor, NW Aquatic Ecosystems, along with UW Botanic Garden IPM staff, will complete initial 2010 treatment on Wednesday, August 18th. The  Waterfront Trail between Foster Island and MOHAI will be closed early am to public temporarily for contractor access to GL growing near the trail. Signs will be posted on barricades at both trailhead entrances and also staffed during spray period to avoid public breaching the barricades. Trail will be reopened once material has dried on foliage. The remainder applications will be accomplished via boat in and around Marsh and other islands and inlets throughout UW Botanic Gardens managed Union Bay shorelines.

Scheduled pm Kayak tours will not be disrupted. Applications within tour boundaries will be completed in am.

There will be a follow-up treatment later in September. Notice will go out as soon as date is set.

For further information, call 206-543-8800


Tree Removal Notice

August 10th, 2010 by UWBG Horticulturist



UWBG tree crew has scheduled the removal of a large standing dead pine collection for Wed. 8/18 and/or Thur. 8/19. Vitals below:

Pinus sylvestris

UW Accession: X-72

Grid 4S-8E

DBH 11.8

Location: Madison Strip

Notes: Standing dead, in decline for several years, oozing pitch near base, possibly caused by boring insects

Wood will be hauled and stump ground ASAP to minimize attracting pine pests.

Targets include:  Street – Washington Place. Trail – S. entry pedestrian path. Other – Plant collections

Temporary road and trail closures and/or detours will be well marked at the site and removal posted at the Graham Visitors center and UWBG website.  Thank you for your cooperation.

If you have any questions, pls contact me via e-mail or phone number below.

David Zuckerman


UW Botanic Gardens

VM 206.543.8008

FX   206.616.2971


Tree Removal Notice

August 3rd, 2010 by UWBG Horticulturist


UWBG tree crew has scheduled the removal of a large standing dead pine collection for Wed. 8/4.  Details below:

Pinus strobus 977-97-E

Grid 35-4W

26″ DBH

Tree has been in decline for several years, possibly due to drainage problems and/or root rot.

Wood will be hauled and stump ground ASAP to minimize attracting pine pests.

Targets include Pinetum Loop trail and other and other plant collections.

Temporary road and trail closures and/or detours will be well marked at the site and removal posted at the Graham Visitors center. Thank you for your cooperation.

If you have any questions, please contact me via e-mail or phone number below.

David Zuckerman, UWBG Horticulture Supervisor,  206-543-8008


Invasive Garden Loosestrife Spraying to Restart

July 29th, 2010 by UWBG Horticulturist

Lysimachia vulgaris imageFor a second year, Northwest Aquatic Eco-Systems along with UW Botanic Garden will begin spray work to control Lysimachia vulgaris (garden loosestrife), a state-listed noxious weed occurring along Union Bay shorelines including the Union Bay Natural Area and the Arboretum’s Foster and Marsh Islands the first week of August.  King County requires control of this aggressive and invasive weed, which poses a serious threat to the native character of area wetlands. In 2009, DoE provided a 5-year grant for $75,000 to fund loosestrife control.

In mid-July members of King County’s Noxious Weed Control Program and UW Botanic Gardens staff mapped the extent of the weed in the areas listed above.  Comparison of the maps from year 1 to year 2 demonstrated slight control had taken place.  Once again the weed will be controlled with an aquatically approved herbicide by the contractor, Northwest Aquatic Eco-Systems using airboats and other specialized equipment.

King County Garden Loosestrife Fact Sheet


What’s the story of Herb Robert at the Arboretum?

July 16th, 2010 by UWBG Horticulturist

On July 14 a UWBG Facebook fan asked us what’s the story of Herb Robert at the Arboretum. UWBG Horticulturalist, David Zuckerman, replies with background information and his personal experience with this stinky weed.

Herb Robert, aka, Stinking Robert. Geranium robertianum is an escaped ornamental herbaceous perennial native to Europe. It has quite a history of folklore and medicinal uses. It is a class B noxious weed in Washington(1998?) and first seen in our state in 1911, Klickitat. Due to its ubiquitous nature in King County, control is currently not required. King County Noxious Weed board strongly encourages and recommends control and containment of existing populations and discourages new plantings.

Personally, my encounters and observations of Bob in the arboretum from 1982 to present:

Started innocently enough as a lovely, cute little scented geranium  and quickly spread into our most troublesome forest shade herbaceous monster in the ‘80s and ‘90s. Now, due to a vigorous weed control program, we have actually reduced its seed bank (from whence it spreads by catapulting tiny black seeds that attach themselves on a filament on the undersides of our Rhododendrons and other forest plant collections and natives).  After hand pulling this weed for many a year, it is NOT recommended to leave one’s gloves hanging indoors to dry out, for the following day you will be hit by a most obnoxious odor reminiscent of the worst possible case of sock and shoe malodorous!

Want to join the fight against invasive weeds in the Arboretum? Volunteer as a Gardener Assistant – we could use your help!