Contact Us Host an Event Volunteer Join

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 Trees Questions

Trees around the inland waterways in Virginia
August 07, 2010 - I am writing a piece about Virginia Beach, Virginia. Could you tell me other than Pine what trees are found in the forests around the inland waterways? Thank-you very much!
view the full question and answer

Non-native, invasive mimosa trees in Vincennes IN
April 29, 2014 - I have 3 Mimosa trees here in Vincennes, Indiana and so far none of them are leafing out this spring (4-28-14) Do you think that this past winter could have killed then?
view the full question and answer

Need source for seeds or plants of Pinus remota in Johnson City, TX..
October 18, 2011 - I cannot seem to find a source for Pinus remota or papershell pinyon pine. Who Grows this? I understand it is rare and would love to try it here in Johnson City. Thanks
view the full question and answer

Native Perennials for Bees and Butterflies in VA
April 15, 2015 - What native perennial plants and trees can we plant to help honey bees and butterfly larvae in Harrisonburg, VA?
view the full question and answer

Spring blooming Acacia farnsiana in Austin
April 04, 2007 - I've been seeing a large shrub, possibly tree, around Austin this spring - and it is covered is small ball-like orangish-yellow blooms - very tightly covered in these blooms. From the car, it looks ...
view the full question and answer

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