A Successful Failure

January 30th, 2015 by Kathleen DeMaria, Arboretum Gardener

The Washington Park Arboretum rang in the new year with a series of windstorms that broke limbs, downed trees and dulled chain saws. What the storms didn’t do, however, was cause extensive damage to collections, structures, or visitors. “Lucky” might be your first thought, but luck had little to do with it. Proper tree care and a knowledgeable and observant tree care crew allow us to consider our recent tree ‘failures’ successful.

UWBG Arborist, Chris Watson ascends a Hemlock that he is removing. Because this is a removal Watson is using spikes on his boots to assist him with his long climb. Spikes are never worn on trees we prune as they can damage bark.

UWBG Arborist, Chris Watson ascends a Hemlock that he is removing. Because this is a removal Watson is using spikes on his boots to assist him with his long climb. Spikes are never used on trees we prune as they can damage bark.

chris ascending shadow

An early morning climb

Our biggest break in January was one of the Hemlocks that line Arboretum Drive. Years ago it developed a ‘double leader’, or ‘codominant stem’ (2 or more main stems with similar diameter that emerge from the same location on the main trunk). Codominant stems can be challenging as the tree grows because the stems push against each other as they grow together, causing deformity that often results in compressed wood and ‘included bark’. These factors can often lead to a weak spot in the tree that may be susceptible to failure.

UWBG Arborist Chris Watson had been monitoring this Hemlock for years and decided to place a cable in the tree a few years ago to prevent any serious breakouts. His decision and placement were both great moves, as this tree did succumb to the wind, but the broken leader remained cabled to the stronger leader and no damage occurred.

Best view in the Arboretum

Best view in the Arboretum. Watson carefully contemplates his next cut.

You have to work hard for the view.

You have to work hard for the view.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Anybody who has ever taken a class in the Arboretum with Dr. Bob Edmonds has likely heard him discuss the fungal pathogen Armillaria mellea, commonly called Armillaria root rot, shoestring root rot, or honey mushroom. Unfortunately we have this pathogen in our soils and occasionally when a tree we suspect has the disease falls, we get a chance to investigate. We (and Dr. Edmonds) suspected this tree had Armillaria.

Tell-tale signs of Armillaria mellea include: White, fan-shaped mycelium growing on the inside of the bark and over the sapwood, soft, spongy and stringy wood that has a lighter yellow coloring, and finally and often most noticeable, black shoestring-like ‘rhizomorphs’ in the dead and dying wood at the base of the tree. Upon investigation of this tree, we did find multiple signs of Armillaria including rhizomorphs, white fans of mycelium, soft spongy yellowed wood, and a column of rot in the center of the trunk that the tree had compartmentalized pretty well over the years.

UWBG’s horticulture staff’s diligent monitoring and tree care regimes turned this failure into a great research and teaching opportunity in our living classroom called the Washington Park Arboretum. Come discover and learn with us.

 

Rhizomorphs from the fungus can be seen here and under a microscope.

Black Rhizomorphs  can be seen here and under a microscope.

Hollow center of this Hemlock indicates decay that the tree has been compartmentalizing for years.

Hollow center of this Hemlock indicates decay that the tree has been compartmentalizing for years.

Soft, spongy and discolored wood where the tree broke indicate the presence of Armillaria.

Soft, spongy and discolored wood where the tree failed indicate the presence of Armillaria.

January Color Appears at the Washington Park Arboretum

January 11th, 2015 by Kathleen DeMaria, Arboretum Gardener
Selected cuttings from the Washington Park Arboretum        (January 5 - 18, 2015)

Selected cuttings from the Washington Park Arboretum (January 5 – 18, 2015)


“Piercing, sucking and galling!”

1)  Mites (on Sasa Bamboo and Skimmia)

  • Stippling and yellowing of leaves are often indicative of the presence of mites.
  • Feed by piercing underside of leaves and sucking chlorophyll out decreasing photosynthesis, reducing plant vigor and compromising the appearance.
  • Mites are not insects; they are arachnids.

2)  Galls (on Willow and Rose)

  • Abnormal plant growths caused by various organisms (insects, mites, fungi, etc.)
  • Galls are formed by increased production of normal plant hormones as response to feeding, egg-laying or disease infiltration and are often not harmful to the plant.
  • Galls can be on leaves, stems, twigs, buds, flowers and roots

3)  Blights (on Hazelnut and Cherry)

  • Refers to a symptom affecting plants in response to infection by a pathogen.
  • Blights come on rapidly and can cause complete chlorosis and browning of plant tissues such as leaves, branches and twigs; plant death is not uncommon.
  • Aided by cool, moist conditions and limited air flow to plants…perfect for the Pacific Northwest!

4)  Phylloxera (on Oak)

  • Microscopic, yellow sucking aphid relatives that feed on leaves and buds.
  • Yellowish spots on leaves in spring turn to brown by summer and defoliate.
  • Repeated defoliation abates photosynthesis and can lead to plant death.

5)  Armillaria root rots (shown on Bigleaf Maple, but many trees are susceptible)

  • Fungus cause stunted leaves, chlorotic needles, dieback of twigs and branches and eventually death.
  • Identified by white mats of fungal mycelium between the inner bark and wood and honey-brown mushrooms growing on or around the base of the tree.
  • A big threat to the lumber industry as the wood is unsalvageable.

Washington Park Arboretum Soil is More Than Dirt

September 26th, 2014 by Kathleen DeMaria, Arboretum Gardener

This past April the Camellia area of the Washington Park Arboretum was paid a scientific visit by UW SEFS professor Dr. Darlene Zabowski and students from her Advanced Soil Genesis and Classification course (SEFS 513). Their goal was to learn how to excavate a soil pit and mine the walls for information about the history of the site, the current state of the soil and potential issues that may need mitigation. The site was chosen by David Zuckerman, Supervisor of Horticulture, as our Camellia collection is in need of a renovation, and he’s a strong proponent of soil analysis prior to any work being done in an area.

As with any good assessment, photos of the site were taken prior to any disturbance:

Camellias before dig

 

This site is located in the south end of the Arboretum just north of the gravel path leading to the newly refurbished lookout in the New Zealand garden. After the leaf litter and duff were cleared, the students started digging, and digging until a 3 foot deep pit was completed (notice the clear separation of ‘horizons’, or layers of soil):

Soil Pit2

In this area 3 feet was needed to ensure that the students got down to the ‘parent material’, or the underlying geological material in which soil horizons form. Soils inherit structure and minerals from their parent material through processes of physical or chemical weathering. This parent material remains the basis of the soil structure as other factors contribute to the soil’s texture (e.g. compaction, amendments, tillage).  According to Dr. Zabowski and her students, our Camellia soil has a parent material in the ‘Alderwood series’, and it shows evidence of compaction and large quantities of amended materials in the upper horizon. There was charcoal found in the middle/upper horizons indicative of a fire in the area (perhaps post-logging) or the charcoal could have come in with amendments added to the soil years ago. The parent material is glacial, composed mostly of ablation till and basal till and the years of amending and alteration can be seen even down into these lower horizons.

Soils layed out

As each horizon was unearthed, Dr. Zabowski (pictured above) had her students lay out a sample of the soil in ascending order to show and feel the difference from one layer to the next. The students were then charged with the task of coding out these samples by color using Munsell Soil Color Charts flip book. Soil color indicates the makeup of the soil within a given geographic area, which can influence the land’s fitness for usage. Samples of each horizon were also brought back to the lab and analyzed for chemical composition, bulk density, base saturation, and Cation exchange capacity (CEC). The Camellia soil was found to have a pH in the slightly acidic region (5.7-6.3), which is good for Camellias, as they like slightly acidic soil. The upper horizons of the soil were found to contain high levels of Ca, suggesting that there had been some CaCO3 added to the soil in the past (the high pH was also indicative of amending with CaCO3). The CEC of the soil was very high in the upper horizons, but this was to be expected at CEC is a measure of the soil’s fertility and nutrient retention capacity and this soil had been amended with organic matter for decades before this assessment (organic matter can have up to 3x the CEC of clay). The bulk density of the soil in the upper horizons suggests that there has been some compaction (likely due to foot traffic as there is a bench near the site) and that remediation of this density should accompany any work done in this area.

The UWBG horticulture staff welcomes and encourages university use of the arboretum for educational purposes as we curate and maintain 230 acres of urban forest as short walk from main campus. Got an idea for research in the arboretum? Contact David Zuckerman at dzman@uw.edu to get your shovels into our soil!

 


August Color Appears at the Washington Park Arboretum

August 17th, 2014 by Kathleen DeMaria, Arboretum Gardener
Selected cuttings from the Washington Park Arboretum (August 11 - 24, 2014)

Selected cuttings from the Washington Park Arboretum (August 11 – 24, 2014)

1)   Poliothyrsis sinensis

  • A rare and very attractive small flowering tree of upright, open habit.
  • Originally brought from China to the Arnold Arboretum by E.H. Wilson.
  • Big 6-8” mildly fragrant, creamy flower clusters (corymbose panicles) make a significant contribution to the August-September garden.
  • Located in grid 30-3E, near the south entrance to the Woodland Garden along Arboretum Drive.

2)   Daphniphyllum macropodum

  • This dioecious plant (translation = “of two houses”) needs plants of both sexes to seed.
  • Our largest grouping sits in grid 7-2E.  This area was recently renovated for the New Zealand Garden construction, allowing more light and air to these plants.
  • Purplish-red petioles, copious berries and leaves arranged in tight spirals make this one of the most asked-about plants in the Washington Park Arboretum.

3)   Veronica salicifolia   (Hebe salicifolia)

  • Is it a Hebe? Is it a Veronica?  Just wait and it might change again!
  • Large, spear-shaped, white flowers populate this New Zealand native in late summer.
  • Salicifolia = “leaf like a Salix (willow)”, hence the common name willow-leaved hebe.

4)   Buplerum fruitcosum

  • This evergreen shrub in the carrot family has striking leathery blue-green foliage.
  • Long-lasting, umbels of greenish-yellow flowers bloom in late spring/early summer.
  • Flowers are highly attractive to a number of predatory insects that feed on aphids and other garden pests.

5)   Argyrocytisus battandieri

  • Commonly called Pineapple Broom, this pea-family plant produces yellow flowers atop blue-gray foliage.
  • Native to Morocco, this plant grows best in full sun and well-drained soil.
  • Located along the west side of Arboretum Drive in grid 16-5E.

Elisabeth C. Miller Garden and Washington Park Arboretum staff walk, talk and gawk

January 11th, 2014 by Kathleen DeMaria, Arboretum Gardener

The Washington Park Arboretum (WPA)  staff was delighted to host the staff and interns from the Elisabeth C. Miller garden for an educational walk and talk Wednesday January 8th. The wind and rain didn’t stop this intrepid group of horticulturists from walking the Pacific Connections Gardens and the ever-changing,  always stunning Joe Witt Winter Garden.  The Miller Garden staff was gracious enough to bring several plants to gift to the WPA, continuing the Miller family’s legacy of supporting the University of Washington Botanic Gardens. A big thank you goes out to Roy Farrow (a former Miller garden intern and current WPA horticulturist) for coordinating this meeting of  plant-world minds.

 

MillerGardentoursWPA2014

Medicinal woody plants growing in the Washington Park Arboretum

December 30th, 2013 by Kathleen DeMaria, Arboretum Gardener
photo

Bark from the Pacific Yew, Taxus brevifolia

1) Taxus brevifolia (Pacific or Western Yew)

  • Native from southern Alaska to central California
  • Chemotherapy drug Taxol was derived from the bark
  • All parts of the plant are toxic except the fleshy red aril surrounding the little green cones

2) Salix (Willows)

  • Aspirin is derived from Salicylic acid (component of Willow-bark extract)
  • Medicinal use dates back to at least the 5th century BC when the Greek physician Hippocrates prescribed it to ease pain and reduce fevers.
  • Lewis and Clark used willow bark tea as a remedy for crew fevers

3) Hamamelis virginiana (Witch Hazel)       

  • Leaves and bark contain hamamelitannin believed to be responsible for astringent properties, hemostatic properties, and antioxidant activity
  • North American Indians distilled bark, leaves and twigs to make eyewash, treatment for hemorrhoids, internal hemorrhages, and gum inflammation.

photo4) Ginkgo biloba (Maidenhair tree)

  • Considered a living fossil, Ginkgo  is native to China
  • Chinese people appreciate the dry-roasted nuts as a treatment for lung qi deficiency

5) Thuja occidentalis (Eastern arborvitae)

  • One of the four plants of the Ojibwe medicine wheel
  •  Rich in vitamin C, thought to have cured many bouts of scurvy in mariners

Source: Moerman, Native American Ethnobotany; Van Wyk and Wink, Medicinal Plants of the World; Schafer, The Chinese Medicinal Herb Farm

A Kiwi Botanist in our Mist

October 31st, 2013 by Kathleen DeMaria, Arboretum Gardener
Bec shows Kathleen how the Maori harvest Muka, the inner fibers of Harakeke (Phormium tennax) to be used in the fabrication of  various fibers used as rope, roofs, shoes, etc.

Bec shows Kathleen how the Maori harvest Muka, the inner fibers of Harakeke (Phormium tennax) to be used in the fabrication of various fibers used as rope, roofs, shoes, etc.

The misty October revealed a great surprise to New Zealand horticulturist Kathleen DeMaria while she was installing signs for the new ‘Lookout Loop Trail’ near the recently restored Lookout Gazebo.  Kathleen and fellow horticulturists Rhett Ruecker and Roy Farrow peeked through the fog and barely saw a highly engaged woman taking notes on the new New Zealand Forest.  As it turns out, this woman was Rebecca Stanley,  Auckland Botanic Gardens Education Officer and former plant ecologist with the Auckland Regional Council. Bec, visiting the US west coast on holiday, graciously offered to spend some time with Kathleen in the garden on the following Saturday. The two plant-geeks spent 4 hours walking through the foggy New Zealand forest. Bec’s encyclopedic knowledge regarding the ethnobotanic uses of plants and the cultural requirements of plants was astonishing, and her willingness to share it all, as well as her educational delivery style were delightful. She offered sources for seed, suggestions for books, names, emails and information about who she knows throughout New Zealand that would be interested and willing to help UWBG grow our own New Zealand forest.  Personally, and as a representative of the University of Washington Botanic Gardens, I would like to thank Rebecca for all of her time and information, it was a delightful walk in the garden topped off with a delicious lunch at Cactus Cafe and a visit to the downtown library. Thanks so much, Bec! All photos courtesy of Julie Postma.

Dew  on Phormium tennax in the New Zealand garden

Dew on Phormium tennax in the New Zealand garden

Bec helps Kathleen assess the health of Olearia nummulariifolia in the NZ forest

Bec helps Kathleen assess the health of Olearia nummulariifolia

Bec discussing perecipitation patterns in the Otago region of NZ

Bec discussing precipitation patterns in the Otago region of NZ

One theory for the 'New Zealand Dead Look' of so many plants: Moa, wingless birds now extinct, were thought to have poor eyesight, so plants would mimic dead plants to avoid predation by these voracious herbivores

One theory for the ‘New Zealand Dead Look’ of so many plants: Moa, wingless birds now extinct, were thought to have poor eyesight, so plants would mimic dead plants to avoid predation by these voracious herbivores

seed capsule of Leptospermum scoparium, or mānuka, the tea tree. This name arose because Captain Cook used the leaves to make a 'tea' drink when he and his scurvy sickened crew arrived in New Zealand

Seed capsule of Leptospermum scoparium, or mānuka, the tea tree. This name arose because Captain Cook used the leaves to make a ‘tea’ drink when he and his scurvy sickened crew arrived in New Zealand

Light breaks through the fog on our walk back to the Visitors Center

Light breaks through the fog on our walk back to the Visitors Center

View from the woodland garden...deciduous trees are rare in New Zealand so Bec was delighted by our spectacular fall color

View from the woodland garden…deciduous trees are rare in New Zealand so Bec was delighted by our spectacular fall color