December 2011 Plant Profile: Ilex x koehneana

December 16th, 2011 by Soest Gardener, Riz Reyes

UWBG has the one of the largest Holly collections in North America and this particular hybrid tends to get by unnoticed until one actually gets up close to admire its bold presence as a broadleaf evergreen shrub. It almost looks like a magnolia or something from the tropics, but it’s perfectly hardly for us here in the Pacific Northwest.

This Ilex is a hybrid between the common I. aquifolium (English Holly) and I. latifolia (Lusterleaf Holly). It does not reseed itself prolifically like English Holly and makes a stately background plant that has endured poor soil, limited irrigation, and is likely to thrive in both sun and part shade.

Common Name: Koehne Holly
Family: Aquifoliaceae
Location: Soest Garden South Slope
Origin: Garden
Height and spread: 15-20ft. high and 10-15ft. wide. Various cultivars exist that are shorter or taller.
Bloom Time: Late spring
Bloom Type/Color/Fruit: Dioecious, white flowers followed by red drupes in autumn/winter on current year’s wood.

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UW Hydrology Study Underway In Holly Collection

April 15th, 2011 by UWBG Horticulturist

Soil test pits indicated by color push pins on map

If any of you have visited the north end of our holly collection in Washington Park Arboretum recently, you probably observed what appears to be a developing wetland. As you may well imagine, standing water where we’re trying to grow healthy hollies just don’t mix very well. See Chris Watson’s post on “Spring Pruning in the Arboretum“.   Why all the standing water? Well, we don’t know.  However, thanks to a collaboration with our School of Forest Resources hydrology professor, Susan Bolton, we may soon have the answers we seek. SFR undergraduate student, Traci Amico, has taken on this investigation as her senior capstone project.  Once we know the source of all the water, we will then be able to plan a viable drainage system that will move the water away from our cherished hollies.  Below is notice for project and will also be posted at site:

  • Notice:  10 soil pits will be dug around the site and monitored on a weekly basis in an effort to determine the source of  flooding in the area.
  • Location:  UW Arboretum, Holly Garden, Lake Washington Blvd and Boyer Ave E
  • Timeframe:  April-May 2011
  • Safety:  Soil pits will be covered and marked with cones

Study Parameters:

I. Soil Pits

a) Data collected from the soil pits will assist in determining soil types and hydrology of the site.

b) After careful consideration of other monitoring processes, soil pits were chosen as the best method for the site because of they are a minimally invasive and relatively inexpensive method of data collection. The pits can be dug with a hand held spade or auger so no heavy machinery will be on the site to further compact the soils. Pits will be dug to no more than 16 inches  and 12 inches in diameter.

c) Pits will be marked with flags and securely covered with plywood to ensure the safety of humans and pets.

d) Exposing soil horizons via soil pits will allow for the visibility of water levels, to ascertain its depth and exposure soil horizons. Monitoring will be done once a week.

e) Suggestions for soil pit locations at the site are below. Google Earth imagery was used.

II. City of Seattle

a) The City of Seattle IT Department has generously offered to let me study   their GIS imagery and plans. With these I will be able to determine the locations of any buried pipes or irrigation and assess the vegetation and hydrology patterns over the years.

III. Google Earth and Aerial Images

a) Google Earth and aerial imaging are both valuable tools in assessing previous vegetation and hydrological patterns at the site due to the historical and 3-D images and ‘real time’ views provided.


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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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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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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.

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