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

Saturday - May 22, 2010

From: Seattle, WA
Region: Northwest
Topic: Trees
Title: Arborvitae and flower garden fighting for space in Seattle WA
Answered by: Barbara Medford

QUESTION:

Hi, I put in dozens of Arbovitae, mature evergreen trees, 4 yrs ago for privacy. They are doing well, but I was surrounding a flower garden which now appears to be suffering due to the root system of the trees. Is that possible? Webs of red roots close to the surface appear to be invading my plants!What do I do now? It is a large area of flowers. Do I replant them(!) and how far from the trees should I have planted? I've been breaking up these roots under the flowers but I now wonder if the trees are soon going to be angry with me for doing that? HELP!!

ANSWER:

The two members of the genus Thuja that are native to North America are  Thuja occidentalis (arborvitae) which is native only to the eastern part of North America, and Thuja plicata (western red cedar), which is native to Washington according to this USDA Plant Profile. It sounds like maybe you visualized a beautiful garden, enclosed with evergreens and full of color, and stepped over some lines.

According to our Native Plant Database: "Western red cedar is a very useful, ornamental conifer. It responds nicely to pruning and is sometimes used as hedge material. It has a slow to medium growth rate, is susceptible to bagworm and heart rot, and is pH adaptable."  From that same page: "The evergreen’s typical height is 50-75 ft., but it can grow to 200 ft. The aromatic foliage is bright green and scale-like, forming horizontal sprays which bronzes to crimson-purple in winter. Large to very large tree with tapering trunk, buttressed at base, and with a narrow, conical crown of short, spreading branches drooping at ends; foliage is resinous and aromatic."

When you say "dozens" of arborvitae, how  big a property are we talking about? The expected size of the trees means they will be actively competing with each other, unless they are spread over quite a large area, and in the competition with the flowers, it's pretty easy to predict which one is going to lose. A tree on its way to being that big is going to be building a BIG root system, as it goes, not to mention casting a lot of shade on everything around it. A standard in estimating how large a root system will extend is that it can be two to four times larger in circumference than the circumference of the crown of the tree. Even though the crown in this case is described as "narrow," the bigger the tree, the wider "narrow" is going to be.

Again, we don't know the exact size or arrangement of your property, but we can probably safely say that no amount of chopping at the roots is going to make a safe place to grow flowers. You planted the trees for privacy, but you may have created the hedge around Sleeping Beauty's castle, through which nothing, including light and people, can pass.  We can't even recommend an action, but you are probably going to have to choose between the arborvitae and everything else. Thinned out to be farther apart, the trees will provide less privacy for right now, but will go on growing, probably better with some of the competition removed. 

We went looking on the Internet for some more information and found this article on Thuja plicata (western red cedar) from Las Pilitas Nursery, which is a favorite source for plants native to California. From this same article, we extracted this quote: "This tree has allelopathic properties." Allelopathy is a fairly recent hot topic in horticulture; it is the ability of a plant to emit substances that will inhibit the growth of plants competing with it for space and nutrients. Those trees have everything going for them: extensive roots, allelopathic qualities, height and size. We don't feel there is any other solution than a realistic rethinking of what you want to do with your garden space. 

Pictures from Google

 

 

More Trees Questions

Problems with a two year old persimmon tree in Fredricksburg, TX.
May 22, 2013 - Hi Mr/Ms Smarty Plants, We planted a 4-ft Texas Persimmon, Diospyros texana, 2-years ago, with wonderful leaf and fruit production since. We recently had a hail storm (5/9/13) and although mos...
view the full question and answer

Small trees for property edge in Katy TX
April 16, 2012 - By deed restriction, I must have five trees on the side of my small suburban lot just west of Houston, TX. Due to the lot layout, the trunks are only about 8-10 feet from the house, with the trees abo...
view the full question and answer

Treating splits in a Cottonwood tree trunk
August 09, 2014 - How to treat slipts in trunk of 4 year old Cottonwood tree.
view the full question and answer

More on preventing suckers on live oaks in Austin
August 01, 2010 - I just received an oak sprout answer id=6021. I have a followup question. Our sprouts are caused by the motte we live in - 12 live oaks on 1/4 acre. I understand we will have to hand dig 1000s of t...
view the full question and answer

Controlling oak suckers in Austin
January 26, 2012 - I live in Austin TX and have one particular native Oak tree in my back yard with a large bed around it. I don't plan on planting anything else in the bed since it is already nicely landscaped along ...
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