En EspaŅol

Q. Who is Mr. Smarty Plants?

A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?

Share

Ask Mr. Smarty Plants

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
    
 
See a list of all Smarty Plants questions
Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.
Need help with plant identification, visit the plant identification page.
 
rate this answer
Not Yet Rated

Thursday - December 16, 2010

From: Oakland, CA
Region: California
Topic: Diseases and Disorders
Title: Problems with Thuja in Oakland CA
Answered by: Barbara Medford

QUESTION:

I have a Thuja hedge about 100' long. Part of this hedge and a well established Rhododendron have been diagnosed with Armillaria mellea that is spreading. I see the bunches of mushrooms growing everywhere. HELP! I imagine that I will have to replace the once beautiful Thujas. What steps must I follow to create privacy from pedestrians and cars (preparation, resistant hedge choices). Thank you for any help you can suggest.

ANSWER:

Because Armillaria mellea is a mushroom and a non-vascular (does not have internal food and water conducting tissues possessed by "true" plants) fungi, we are unfamiliar with how it interacts with other plants. From MushroomExpert.com, Armillaria mellea: The Honey Mushroom, gives you much more information on that than we could. From that article, here is an extract that locates the plant and its target hosts:

"The classic honey mushroom, Armillaria mellea, turns out to be limited to roughly the eastern half of North America, from about the Great Lakes to the Gulf Coast and the East Coast--and perhaps to northern California, where it has been reported. It usually grows in clusters on hardwoods, but is occasionally found on conifers. It has a fairly smooth cap, a sturdy ring on the stem, and fused stem bases that are tapered to points. Under the microscope, it has basidia that are not clamped at their bases."

Oakland, on the San Francisco Bay appears to be in USDA Hardiness Zones 10 to 11, approximately in the middle of the state; that is considered Northern California.

There are two members of the Thuja genus native to North America:

Thuja occidentalis (Arborvitae) - this USDA Plant Profile shows that it does not grow west of Minnesota nor in any of the southeastern United States

Thuja plicata (Western arborvitae) - USDA Plant Profile indicates it grows in 3 counties in Northern California, but these maps can become out of date. Pictures from Google.

So, you have one plant (Thuja occidentalis (Arborvitae) that should not be growing in your area at all, and one  (Thuja plicata (Western arborvitae)  plus the Armilleria mellea that might not grow in your area. It is always essential, before you purchase a plant, to determine if it belongs in the area where you are gardening. If you have Thuja plicata (Western arborvitae) our webpage on that plant states that it is very resistant to rot. Since we do not know the answers to these questions, we will proceed as best we can on what you should do next. If a local expert has made the diagnosis we will defer to that, since we are not on the spot, and probably wouldn't know which is what, if we were on the spot.

We made all the above comments to help you understand that perhaps the selection of a conifer such as Thuja for your area may have been the original mistake. Our second thought is that, although this perhaps does not constitute a complete monoculture, 100' of the same plant is certainly inviting trouble if they all contract the same problem and/or transmit it among themselves. We are going to go to our Recommended Species section, select on Northern California on the map, and then choose "tree" from the drop-down menu on General Appearance. You may also, in that right hand sidebar on the page, indicate soil moisture and amount of sun available. We will do a sample list for you, and recommend that you read each webpage on the specific tree and also follow the link at the bottom of the page to Google on that plant and, using the same method, make choices of your own. If your plants have a disease carried in the soil, you will have to find plants whose roots can withstand whatever is causing the rot. We also suggest you contact the people at the University of California Extension Office, Alameda County, to see if they know what is going on. We could find no conifers native to your area; perhaps they don't like that warmth and low altitude.

From our Native Plant Image Gallery:


Thuja occidentalis

Cercocarpus montanus var. glaber

Cornus sericea ssp. sericea

Quercus agrifolia

Umbellularia californica


 

More Diseases and Disorders Questions

Need help with a 50 ft Tulip Tree with storm damage in Brownsburg, IN.
June 30, 2010 - I have a 50 ft Tulip tree that suffered storm damage. One for the main branches split at the top fork and fell. It has left about 6 ft of exposed wood but there are still a couple of main branches in...
view the full question and answer

Why is my recently planted Esperanza doing poorly in Texas City, TX?
May 28, 2010 - I have an Esperanza I planted about 2 months ago. It has been doing well, except today all but one stem of the plant is wilting and the leaves are rolling. I see no bugs on the plant. Any idea what...
view the full question and answer

Dry browning leaves on Monterrey Oak from San Antonio
August 08, 2013 - I have a Monterey Oak that was planted four years ago and was doing great until the last two weeks. It has turned brown and the ends of the branches are very dry and brittle. The root flare was cov...
view the full question and answer

Browning leaves on recently planted chinkapin oak in Rockwall TX
June 09, 2010 - I just planted a chinkapin oak that is about 1 1\2 inches thick last week and now some of the leaves are turning brown. Does that mean its dying? Do you have any tips that I could use to protect it?
view the full question and answer

Leaf cutter ants in potted Mexican lime tree
May 21, 2008 - Hi, I'd like to add a question to the recent post about leaf-cutter ants. I have a potted mexican lime tree that has been inhabited by an ant colony for several months. They are chewing holes in th...
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | SITEMAP
© 2014 Lady Bird Johnson Wildflower Center