Horticultural Updates

By Margaret Bayne, OSU Extension Staff-retired, OSU Master Gardener

October 2017

 “A Gardener’s Primer to Mycorrhizae: Understanding How They Work and Learning How to Protect Them,” a great new publication from WSU’s

Mycorrhizae. Photo: WSU

Dr. Linda Chalker-Scott.  “Mycorrhizae are symbiotic associations between many plants and the beneficial fungi that colonize their roots. Gardeners are often unaware of these relationships and may inadvertently injure or kill the beneficial fungi through common gardening activities. This publication will help home gardeners understand the benefits of mycorrhizae and explain how to enhance their presence in landscapes and gardens.”(Linda Chalker-Scott, Publication FS269E, WSU) http://bit.ly/2ephLqh

Physiological Effects of Smoke Exposure on Deciduous and Conifer Tree Species.” There is not a lot of information on how the smoke from the recent fires will affect our plants, but here is an interesting study discussing how smoke affects forest trees. (W. John Calder, Greg Lifferth, Max A. Moritz, and Samuel B. St. Clair; International Journal of Forestry Research) http://bit.ly/2wzGuDA

Tell little girls that it is never too early to learn about bugs! “An 8-Year-Old Bullied For Her Love of Bugs Just Got Her First Scientific Publication.” (Signe Dean, Sciencealert.com) http://bit.ly/2fpi8C9

President’s Clematis. Photo: OSU

Clematis put on a special show in the garden as they climb up trellises and trees unfurling large, lusciously colored flowers! These garden favorites need a little special handling at the start but once established clematis grow and flower year after year. (Kym Pokorny, OSU)

Did you know the first space travelers were seeds? Learn what scientists are up to now. (Gina Riggio, U of Arkansas; Theconversation.com)

24 Ways to Kill a Tree! (What you shouldn’t do) and 24 ways to NOT kill a tree (what you should do). “Few residential trees die of “old age.” Mechanical damage and improper tree care kill more trees than any insects or diseases.” (Bonnie Appleton, Publication 430-210, Virginia Cooperative Extension) http://bit.ly/2wmEQjP

Watch the five finalist videos in the 2017 “YouTube Your Entomology” contest:  (Entomologytoday.org) http://bit.ly/2w8EePC

Can You Pick the Bees Out of an Insect Lineup?  Take the quiz and learn more! (Joanna Klein, NYtimes.com) http://nyti.ms/2gZ8Ht5

“Tolkien’s Plant Passion Moves Botanist to Create Guide to Middle Earththe retired botany professor spent years cataloging every plant that appeared in his writing, eventually compiling a list of 141 different species. He teamed up with his son, Graham, a professional illustrator. And together, they embarked on quest to transform that list into a botanical guide to Middle Earth.” (David Fuchs, NPR.org) http://n.pr/2xj1iwv

Did you know that referring to our North American representatives as ‘asters’ is no longer taxonomically accurate? Learn why from the article,

Aster. Photo: OSU

How North America Lost its Asters.” (Indefenseofplants.com) http://bit.ly/2jMr3BV

Insects have much better vision and can see in far greater detail than previously thought, a new study from the University of Sheffield has revealed.” (Eurekalert.org, University of Sheffield) http://bit.ly/2wAfvrG

“These Five “Witness Trees” Were Present at Key Moments in America’s History. These still standing trees are a living testament to our country’s tragic past.” (Mike Yessis, Smithonian.com) http://bit.ly/2fC6JPe

Natter’s Notes:
Pear Trellis Rust, a new disease

Jean R. Natter, OSU Master Gardener

Recently, Pear Trellis Rust (Gymnosporangium sabinae) became the newest contributor to this hodge-podge-let’s-try-everything year. During 2016, the first case of pear trellis rust was reported in the northern section of the Willamette Valley, that on a Bartlett pear growing in Milwaukie, Clackamas County. (See “Pear Trellis Rust: First Report in Oregon” Metro MG Newsletter, January 2016;  http://extension.oregonstate.edu/mg/metro/sites/default/files/dec_2016_mg_newsletter_12116.pdf). Then, in mid-September 2017, an inquiry about a pear leaf problem in Multnomah County was submitted to Ask an Expert. [Fig 1; Fig 2] Yes, it’s another fruiting pear tree infected with trellis rust. It seems that gardeners are beginning to recognize this newcomer.

“Symptoms [of trellis rust] on pear begin as yellowish-orange leaf spots early in the season. Young fruit and twigs can also be infected. Leaf spots can become bright reddish orange during the summer. By mid-summer, tiny black dots (pycnia) appear in the center of the leaf spots.” [Fig 3] By late summer, brown, blister-like swellings form on the lower leaf surface just beneath the leaf spots. This is followed by the development of acorn-shaped structures (aecia) with open, trellis-like sides that give this disease its common name. (Fig 4) Aeciospores produced within the aecia are wind-blown to susceptible juniper hosts where they can cause infections on young shoots. These spores are released from late summer until leaf drop.” (“Pear Trellis Rust, Gymnosporangium sabinae” (http://www.ladybug.uconn.edu/FactSheets/pear-trellis-rust_6_2329861430.pdf)

Signs on affected alternate host junipers are difficult to detect. During wet weather in spring, look for swollen areas on branches which exude orange jelly-like horns.

Differentiate Trellis Rust from Pacific Coast Pear Rust

Trellis Rust is quite different from the widespread Pacific Coast Pear Rust you’ve likely seen every spring on Amelanchier (shadbush; serviceberry) and pears.

Pacific Coast Pear Rust infects both Asian and European pears.  And, as is common with rusts, it also has an alternate host. During spring, host incense cedars (Calocedrus decurrens) are recognized by the bright orange jelly-like globs on the foliage. On pears, the bright orange, powdery spores erupt on fruits, flowers, leaves, and twigs, often deforming them. [Fig 5; Fig 6] Management includes removing nearby hosts. A home-use spray is available for ornamental pears but not edible pears. (Keep current with the PNW Disease Management Handbook.)

Management strategies for trellis rust                             

Minimizing overhead irrigation might help reduce the number of infections. But you know how Oregon springs are.  It rains! Cultural management may help decrease infection rates:

  1. Collect and discard infected leaves.
  2. If practical, remove juniper hosts from a 1000-ft radius. (The PNW Disease Handbook states “J. communis, J. horizontalis, and J. squamata are immune or highly resistant.”)
  3. No chemical remedies are available for edible pears.

Master Gardeners as First Responders

When MGs see a plant affected by a disease or insect, we’re required to verify our tentative diagnosis before we suggest a remedy. So, here’s an important project for you: Help track the spread of Pear Trellis Rust.

If you suspect pear trellis rust while volunteering at the MG Offices or elsewhere in the metro counties, request images and/or samples. Take pictures and jot down a history with at least these few facts, if known: the name and age of the pear; when the client first detected the problem; also, in which town the tree grows. Next, email the images and history to me (j.r.natter@aol.com). After I verify your tentative diagnosis, I will notify both you and the pathologist.

Image of Pear trellis rust
Fig 1: Pear trellis rust (Gymnosporangium sabinae) on the top leaf surface of edible pear tree; Multnomah County, OR. (Client image; 2017-09)

Fig 2: Pear trellis rust (Gymnosporangium sabinae) on the reverse of a leaf from an edible pear tree; Multnomah County, OR. (Client image; 2017-09)

Pear trellis rust
Fig 3: Pycnia (the black dots) of pear trellis rust on the upper leaf surface are involved in development of infectious structures on the underside. Bartlett pear tree; Milwaukie, Clackamas County, OR. (R. Frick-Wright; 2017-09)

Click the link below for a PDF containing the above text and all the images.

Pear Trellis Rust PDF


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Natter’s Notes: Heat Stress

Jean R. Natter, OSU Master Gardener

September 2017

This has been an interesting year as far as plant problems go. The past winter was colder than usual; this spring was wetter than usual; this summer hotter and drier than usual; and, oh yes, we had a total solar eclipse (2017-08-21) even as I was writing this. Then, too, in spite of the plentiful rainfall this past winter and spring, established trees in forests and landscapes are dying from consecutive years of drought.

For the most part, causal agents of plant problems are abiotic, caused by naturally-occurring adverse environmental factors, also the garden’s care-takers, John and/or Jane Doe. So, when clients ask which disease afflicts their plants, we have a lot to consider. We need a detailed history of what occurred and when, including pre-plant preparations as well as follow-up maintenance.

Just how plants react to high temperatures depends upon numerous factors, among them the extent and duration of the heat; the relative humidity; wind conditions; soil moisture content; the kind of plant, its age, site, and general status before the heat hit. (Phew! That’s a lot to consider.) Sometimes leaves are only damaged superficially.  Other times, tissues die. Tissue survival is most likely when the plant is fully hydrated well before the heat hits. If heat is predicted, water the night before or early morning, between 2 and 6 AM.

One good thing about the recent heat waves, the accompanying low humidity has helped limit common leaf diseases. Well, except for powdery mildew, the fungus that creates a whitish film on the leaf surface. If that’s the case, recall that most fungicides are preventive and must be applied at the very first sign of disease, long before the leaf is snowy white.

Accurately diagnosing heat damage relies, in part, upon how well you “read” the signs and symptoms. It’s a skill that requires time to develop. (You know the old saw: Practice, practice, practice.)

Let’s take a look at how heat damage may be expressed, especially on leaves, since that’s often the only thing a client submits for diagnosis.

Young dogwood (Cornus sp.), probably about 2 years old, in a commercial landscape. (Fig 1) Exposure to bright sunlight damaged superficial tissues, killed the chlorophyll (green), revealing the underlying anthocyanins (red pigments), resulting in a reddened sheen on only the most exposed leaves.  The somewhat shaded leaves retain excellent green color.

Signs of heat stress on dogwood leaves
Fig 1 – Superficial heat damage to dogwood leaves (Cornus sp.) which killed the green pigments near the leaf surface, thereby revealing the underlying red pigments. (J.R. Natter; 2017-08

Vine maple leaf with dry, brown edges, evidence of acute water shortage to the shrub. (Fig 2) Sudden heat exposure to a 19-year-old shrub damaged many leaves in a wide swath across the shrub. Affected leaves were tan and shriveled while others only had dry edges. Client wondered if the tree was at the end of its life span. The Ask an Expert response, said essentially this: It’s the recent heat. (Client image; 2017-08) Click image for larger view.

Vine maple leaves suffering from heat stress
Fig 2 – Vine maple leaves, damaged by heat and sunlight. Owner asked if the 19-year-old tree had a disease. Another vine maple, planted at the same time, was fine. (Client image submitted to Ask an Expert; 2017-08)

Hosta, exposed to sudden and extreme heat, accompanied by low humidity. (Fig 3) The most severely damaged tissue at the right edge of the leaf, outlined by a zone of white tissue, still retains normal color. This kind of damage can develop in susceptible plants even if they’re in full shade. (J.R. Natter; 2017-06-24)

Heat Stress on Hosta plant
Fig 3 – Hosta leaf, damaged in less than a day, by searing heat and low humidity that dried the tissue so rapidly it retained its normal color. The crisp, dry zone at the periphery is separated from healthy tissue by a narrow white zone. (J.R. Natter; 2017-06)

Click link below for PDF with additional information and images:

2017-09 Heat stress_Natter’s_Notes

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Where but in a garden do summer hours pass so quickly?  – Anonymous

Summer greetings!  We hope your gardens are flourishing in these high summer months.  July and August are good months to sit back, enjoy your garden, and of course spend some time wearing your volunteer hat as an OSU Master Gardener!


Phones are ringing!  Questions are flying into the Master Gardener phone clinics via email, phone calls, and visitors to our offices.  This is a great time to expand your knowledge, collaborating with other MGs as you research and advise gardeners regarding their gardening conundrums.  Sign-up on CERVIS or contact a phone coordinator.

Clackamas County Phones, Jean Bremer, 503-655-8631 jean.bremer@oregonstate.edu
Multnomah County Phones, Susan Marcus, 503-703-4937 susanmultphones@gmail.com
Washington County Phones, David Butt, 503-645-5769 dandubutt@gmail.com

Farmer’s Markets are busy and vibrant with a bounty of summer vegetables and fruits, plus lots of inquiring minds seeking answers to their garden questions.  Each market has its own special qualities.  Discover those unique traits by volunteering at a few farmers markets new to you.  Grab an open slot on CERVIS  Don’t despair if market schedules appear full.  Check back often as schedules change and openings arise throughout the summer.  Let a clinic coordinator know you if you are willing to serve as a substitute for last minute cancellations at your favorite market.

Summer Farmer’s Markets:  Beaverton – Gresham – Hillsdale – King – Lake Oswego – Lents – Milwaukie – Oregon City – Sherwood – Tigard



Oregon and County Fair FUN!

If you want a big dose of summer fun, sign-up for an MG Clinic table at one of the county fairs or the Oregon State Fair.  Give sage (OSU proven), garden advice to fair visitors and take a bit of time, before and after your shift, to grab some shaved ice and check out the fair competitions whether it is honey products, the biggest homegrown fruits and veggies, or the best home brew or chocolate layer cake!  Sign-up on CERVIS to grab a shift now!  Admission passes and instructions provided to all fair volunteers.

Clackamas County Fair, August 15 – 19 (Tuesday – Saturday). MGs are in a prime location at the Clackamas County Fair with our clinic table right by the entertainment stage, lovely display garden and plant sale. Join-in!   Sign-up on CERVIS or contact coordinator Jane Collier: carushill@web-ster.com, 503-266-1191.

Washington County Fair, July 27 – 30 (Thursday – Sunday). Nestled right next to the demonstration gardens is the perfect location for the MG clinic. This area of the fairgrounds owes its planning and attractive appearance to the Washington County Master Gardeners and is a popular stop for fairgoers.  Yes, MGs have bragging rights for this beautiful feature of the fair grounds.  Come see it!  Sign up on CERVIS or contact Margery Brunello: mbrunello11@hotmail.com or 973-699-2304

Oregon State Fair, September 1-2. For the ultimate fair experience, take a quick jaunt to Salem for the Oregon State Fair.  Master Gardeners from around the state host the OSU Extension Master Gardener Clinic.  Our Metro MG program does the honors on Friday and Saturday, September 1st and 2nd. Don’t miss this festive state celebration! Sign-up on CERVIS or email Jordis Yost, jordis.yost@oregonstate.edu and ask for a morning, afternoon, or evening shift on Friday, or Saturday.

Get Volunteering! CERVIS will get you there!

All of the OSU metro MG Program volunteer activities are available for sign-up on CERVIS, our online volunteer registration system (for Partner activities contact coordinators). Go to the “Volunteer Portal” link found on the right side of our main website page.  Then find the “CERVIS volunteer event registration” link.

When logging into CERVIS for the first time, enter your email and click on “Don’t Know password/ Reset password” to get a temporary password.

Please only sign up for events that you know that you can attend. If you need to cancel an event, please contact the clinic coordinator for a list of other volunteers interested in serving as substitutes. It is your responsibility to find a backup.

advisory group photo
MG program Manager Weston Miller providing instructions for lively group discussions about the MG program’s future outlook. Photo by: Marcia McIntyre

Moving Forward…
Master Gardeners Advise Program

An engaged and thoughtful group of 40 Master Gardeners convened on Tuesday, June 6th for a Metro Master Gardener Advisory meeting.  Using the 2014-2019 Metro Master Gardener Strategic Plan as a prompt, participants broke into three groups for a brainstorming session, offering suggestions and recommendations for the program moving toward the future.  Lively discussion ensued, with the compilation of many thoughtful and insightful suggestions.  Program staff greatly value the input and creative ideas.  These suggestions will be further explored via upcoming Master Gardener Liaison Meetings.

Master Gardener Liaison Meetings are open to all Metro Master Gardener volunteers.  Upcoming meetings:

  • Tuesday, August 8 10am to 12noon, Washington Co. (location TBA)
  • Tuesday, October 10 10am to 12noon, Clackamas Co. (location TBA)
  • Tuesday, December 12 10am to 12noon, Multnomah Co. (location TBA)

There will also be a special meeting to explore the use of technology in the Master Gardener Program following the August 8th Liaison Meeting. The technology meeting will be from 1:00pm to 3:00pm.  Look for an email invitation to the Liaison Meetings in the next couple of weeks (RSVPs required for all meetings), with details on specific locations which will rotate among the three counties.

Hands-on in Demonstration Gardens
Summer is a glorious time for hands-on learning in any of our ‘Partner’ demonstration gardens.  Each garden offers unique active, relevant, learning opportunities.  Contact a coordinator and dig in!

Hopkins Demonstration Forest
Frank Wille 503-342-6699 franklyna@comcast.net

Grow-An-Extra-Row and Learning Garden’ at Clackamas Community College
Nancy Muir 503-789-697 ccmgextrarow@gmail.com  

End of the Oregon Trail Pioneer Garden
Kathy Turner 503-630-5794 turnerkathy@yahoo.com

Community Demonstration Garden – SE Portland
Heidi Nichols at heidinichols@comcast.net
Nancy Fine at mcmgdemogarden@gmail.com

Washington County Fairplex Garden
Bob Campbell 503-691-6708 rac223@hotmail.com

Learning Garden at Jenkins Estate
Sandy Japely 503-531-8482 sjapely@gmail.com

International Rose Test Garden in Washington Park Photo credit:

Beautiful, historic gardens.
Consider spending time this summer in a beautiful, garden – dispensing reliable gardening information.

It is a very special year at Washington Park International Rose Test Garden.  Sign-up for a shift as the garden celebrates its Centennial year!

The Pittock Mansion is another lovely and historic setting in which to share your garden knowledge.

Sign-up for a shift via CERVIS or contact the clinic coordinators.

Log Your Hours
Thank you for your passion, energy and volunteer service educating the gardening public.  We want to be sure to have a record of all your efforts.  Here is the link you need for the forms to log your volunteer hours.  Choose from a PDF or Excel form.  All hours due by October 1, 2017.  http://extension.oregonstate.edu/mg/metro/forms

MG Nuts and Bolts
Need a refresher on how to maintain your Master Gardener certification?  All the nuts and bolts can be found here!

Save the Date!  Saturday, October 28th FALL RECERTIFICATION!

Our annual Master Gardener Fall Recertification Training is scheduled for Saturday, October 28th, 8:00am to 3:30pm, at Clackamas Community College.  This annual event is a daylong continuing education opportunity.  Earn 6 hours of continuing education/recertification credit by attending.

A great line-up of speakers is forming.  This year’s presenters all bring their wealth of experience from their work with OSU Extension Service.  They will offer a wide range of topics to enrich the knowledge base of Master Gardeners.  They are Joy Jones, Sam Chan, Brooke Edwards and our very own Weston Miller.

The Fall Recertification day also gives us the opportunity to congratulate the new class of trainees as they step up to Veteran status after completing their volunteer requirements.  We will present trainees with their OSU Extension Service Master Gardener badges and a big shout out for successfully completing the program.