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Thursday - April 23, 2009

From: Lebanon, IN
Region: Midwest
Topic: Non-Natives
Title: Toxicity of non-native Royal Empress tree
Answered by: Barbara Medford


We want to plant some fast-growing trees for shade for my horses. My friend wants to use Royal Empress trees. Can you tell me if these are toxic to horses (and also goats)? I have a lot of clay in the soil on my property.


The first thing we want to do is urge you NOT to plant the Royal Empress tree, for reasons you will learn from this Plant Conservation Alliance Alien Working Group website on Paulownia tomentosa. It is a native of western and central China, and can quickly become invasive, crowding out or destroying more desirable native plants. As in the case in other fast-growing trees, it is a weak tree and not long-lived. At the Lady Bird Johnson Wildflower Center, we recommend only plants native not only to North America but to the area in which the plants are being grown. Plants native to an area will be adapted to the climate, rainfall and soils, and require less fertilizer, water and maintenance.

Now, for what plants are poisonous to horses, excerpted from a previous Mr. Smarty Plants answer:

Answer: First of all, Mr. Smarty Plants wants to refer you to some plants to AVOID for your horses.  Please see the lists from the following sources:

10 Most Poisonous Plants for Horses from EquiSearch.com

Poisonous Plants from Trailblazer Magazine

Toxic Plants: Horses from the ASPCA

Horse Nutrition: Poisonous Plants from Ohio State University

Next, Mr. Smarty Plants refers you to our Recommended Species page to find native plants that are commerically available in Indiana.  You can select 'Indiana' from the map or pulldown menu and then NARROW YOUR SEARCH by selecting 'Tree' from the Habit (general appearance) option.

You might also check for recommended species near your area (Boone County) on the Indiana Native Plant Society website.

Finally, Mr. Smarty Plants refers you to some toxic plant databases that you can check for the plants you like.  These would be:  Poisonous Plants of North Carolina, Cornell University Plants Poisonous to Livestock, Texas Toxic Plant Database, and University of Pennsylvania Poisonous Plants.  When you find a tree that you would like to plant in your pasture, you can compare it with these lists to see if it is safe for your horses.  From the Indiana Recommended species list mentioned above, Mr. Smarty Plants has chosen several species and checked them against the toxic plant databases.  These species are:

Carpinus caroliniana (American hornbeam)

Carya ovata (shagbark hickory)

Platanus occidentalis (American sycamore)

Carpinus caroliniana


Carya ovata

Platanus occidentalis

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