Rent Shop 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?


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
Not Yet Rated

Thursday - April 10, 2008

From: Rigby, ID
Region: Rocky Mountain
Topic: Poisonous Plants
Title: Fast growing trees in Idaho
Answered by: Barbara Medford


I want to plant fast-growing trees on my property in Idaho. What trees are poisonous to horses and dogs? I am particularly interested in the Royal Empress (Paulowmia) tree and the dogwood tree.


We don't like to start out with discouraging words, but Paulownia tomentosa is NOT a good choice. We have been asked about it several times, and would like for you to read a previous answer from Mr. Smarty Plants on the subject. Next, read this site from the Plant Conservation Alliance "Least Wanted" List. It appears that some have already escaped cultivation and invaded Idaho; but, under the circumstances, we certainly hope you do not contribute to the problem. The tree is a native of China and, as such, is not normally in the purview of the Lady Bird Johnson Wildflower Center. Our focus and concentration is on plants native to North America; however, we are very interested in invasive plants, especially non-native invasives.

Now, on to the dogwoods, genus Cornus. We found fourteen species of Cornus on our Native Plant Database, of which four can apparently be grown in Idaho.

Cornus canadensis (bunchberry dogwood) This is really a low-growing groundcover type of bush, probably not what you had in mind.

Cornus nuttallii (Pacific dogwood) This USDA Plants Profile shows the areas in Idaho where this species is growing naturally. It is a deciduous tree up to 40 feet tall that does best between 3000 and 8000 feet in altitude. Unfortunately, it is very susceptible to dogwood anthracnose, which has killed many larger plants in the wild and also restricts its use as an ornamental tree.

Cornus sericea (redosier dogwood) Both of these sericea dogwoods are recommended for Idaho, and are useful for erosion control.

Cornus sericea ssp. sericea (redosier dogwood)

Since none of these seem to be the perfect choice, how about some alternatives? First, for the Empress Tree. We went to our Invasives website and found four alternatives to this tree; unfortunately, none of them are recommended for Idaho. So, we went shopping in the Recommended Species for Idaho section and have four tree suggestions. We realize that you wanted fast-growing, blooming trees, but it may be that is not going to happen in Idaho.

Acer grandidentatum (bigtooth maple)

Betula occidentalis (water birch)

Pinus contorta (lodgepole pine)

Prunus virginiana (chokecherry)

And, finally, your question about what trees are poisonous to horses and dogs. Rather than reproduce the list, let us refer you to this Poisonous Plants Informational Database from Cornell University.

Cornus canadensis

Cornus nuttallii

Cornus sericea

Cornus sericea ssp. sericea

Acer grandidentatum

Betula occidentalis

Pinus contorta

Prunus virginiana




More Poisonous Plants Questions

Is non-native cotoneaster poisonous to goats from Eureka CA
August 19, 2011 - I have heard that cotoneaster is poisonous to goats and other animals. We are trying to get rid of it in our yard, but I was hoping we could use goats to eat it back. What are our options in removin...
view the full question and answer

Identity of plant with thorns in Maryland
August 27, 2013 - I live in Maryland and was walking in the woods one day when I accidentally stumbled in to a thorn bush. I don't remember what color the thorns where or very much about the plant in general but I do ...
view the full question and answer

Fall care for Fan Scarlet lobelia in Rock Island IL
November 09, 2009 - What do I do with Scarlet Fan lobelia in the fall; do I cut it back or let it go as is?
view the full question and answer

Indoor and Outdoor, Fast Growing Plants for California
October 22, 2015 - Iím looking for the best plants for me. I have small kids so they would have to be safe. I would like them to be able to grow inside or outside. I would love for them to grow fast and reproduce fast.
view the full question and answer

Plants to replace poison ivy and brush
June 23, 2008 - I am right next to a highway in Paradise, CA 95969. I am having brush and poison oak removed in that area and want to plant something fast growing and draught resistant. I am thinking about Oleander...
view the full question and answer

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