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University of Washington Botanic Gardens

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Washington Park Arboretum
Center for Urban Horticulture

Horticulture Updates

Fragrance Garden renovation enters phase two

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
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Arboretum Loop Trail nears construction start

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

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

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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.”

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