Host an Event Volunteer Join Tickets

Support the plant database you love!

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

Please forgive us, but Mr. Smarty Plants has been overwhelmed by a flood of mail and must take a break for awhile to catch up. We hope to be accepting new questions again soon. Thank you!

Need help with plant identification, visit the plant identification page.

 
rate this answer
1 rating

Friday - April 09, 2010

From: Bucks County, PA
Region: Mid-Atlantic
Topic: Shade Tolerant, Trees
Title: Arborvitae thinning in Bucks County, PA
Answered by: Barbara Medford

QUESTION:

My arborvitae trees are about 11 ft. tall. I had them put in about 3 years ago. They were 8 to 10 ft. when planted. After the first year, I have noticed they are thinning to the point where you can see right through them. What can I do to make them full like they once were, or are they dying? Any help would be much appreciated.

ANSWER:

Bucks County in the southwestern corner of Pennsylvania and USDA Hardiness Zone 6b would seem to be the appropriate place for  Thuja occidentalis (arborvitae) to grow.

However, we picked up some facts that may explain the thinning of your plants; the first was from our webpage on Thuja occidentalis (arborvitae).  That offered the information that in a crowded environment, this tree is slender and not well-branched. In the open, it improves in form and density. This Ohio State University site commented that it prefers a moist, well-drained, loamy soil in full sun, but tolerates soils that are poor, rocky, clay, compacted, dry, and of various pHs extremely well, and is very urban tolerant to heat, drought, humidity, and pollution; however, not tolerant of shady situation. From that same article, we also learned that old foliage from the self-shaded middle of the shrub abscises (sheds) noticeably in Autumn, and falls through the interior of the canopy directly to the ground below.

Our conclusion is that if your arborvitae are not in an open area, with plenty of sun, that is probably causing their decline. They are not likely to be dying, but are not going to prosper as much as you might wish. Some of the openness is no doubt the result of the shedding of the interior branches, caused by the plant's own shade, which you can hardly do anything about. 

Pictures of Thuja occidentalis (arborvitae) from Google

From our Native Plant Image Gallery:


Thuja occidentalis

 

 

 

More Shade Tolerant Questions

Want salt, shade, drought tolerant plant for Rochester, New York
September 21, 2010 - I am looking for a ground cover plant for western NY to grow on a strip alongside a road that gets very little sun in summer (lots of tree branches shading it). It gets a lot of road salt in winter a...
view the full question and answer

Butterfly plants from Austin TX
December 17, 2012 - I have a butterfly garden in the front part of the house facing the south side. However it is also mostly under a few Oak trees that cast shadow over half of the front yard starting early afternoon. ...
view the full question and answer

Shade tree for cemetery in Wilmington DE
September 13, 2009 - We are looking for a shade tree for a cemetery in Delaware. The tree will be planted only a few feet from some existing gravesites. What trees would you recommend that will not interfere with the ...
view the full question and answer

Perennial Suggestions for Under Ash Trees in Minnesota
June 12, 2013 - With our house we have inherited 2 ash trees in our front yard with a large amount landscaping underneath. I'm replacing the landscaping but there are tree roots at the surface preventing me from bei...
view the full question and answer

Native grasses to accompany buffalograss in shade
May 01, 2008 - What grass goes with buffalo for shade/partial shade?
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.