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Old 05-10-2006, 04:33 PM   #1
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Location: Washington State
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Walnut Trees

I know that horses can have bad reactions to sawdust made from black walnut and also if they were to eat the leaves, but I'm wondering about Carpathian Walnut. I've tried to research it but haven't been able to find out if there's a difference. We bought a walnut tree that we were going to put in the corner of our pasture, but now I'm worried that if they try to eat the leaves for some reason we'll have a problem. Anyone have any experience with this?
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Old 05-10-2006, 06:53 PM   #2
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Don't know - all the references I can find on horse toxicity point to black walnut but not Carpathian. Following is an extract from an Equus issue last year:

Toxic Tree Patrol
Equus Magazine, September 2005 Issue
Late summer is typically a time of increased storm activity. The resulting high winds can bring down tree branches and
blow in foliage from neighboring properties. If debris from a toxic species ends up in your pasture, your horse may be
tempted to nibble the foliage, putting him at risk of serious illness or death. Before the next storm, inspect your property
for the following species (arranged from the most deadly to the least).

• yew (Taxus spp.)
• oleander (Nerium oleander)
• red maple (Acer rubrum)
• cherry (Prunus spp.)
• black walnut (Juglans nigra)
• black locust (Robinia pseudoacacia)
• horse chestnut, buckeyes (Aesculus hippocastanum)
• oak tree, acorns (Quercus spp)
• Russian olive, oleaster (Elaeagnus angustifolia)

Carpathian walnuts aren't listed and they are English rather than black, and I can't find a direct reference they are toxic to horses. Although they are a different species, they share their family name with black walnuts.

Unless you can find a definitive answer somewhere, I would advise to be on the side of caution. T-man is a good researcher. Maybe he can find something more definitive...
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Old 05-10-2006, 10:08 PM   #3
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Aha! found an answer, this is from a Google question and answer page

Personally, I wouldn't worry if the tree were outside the pasture - well outside, like 60-80 feet, escpecially if it would be the lone tree out there. Your horses would then use it for shelter, and would likely be poisoned to some extent. Also, since it is a nursery tree, it may be grafted onto a black walnut root (very likely, if it is to survive the climate in Washington), which would poison the forage under the tree (the roots are the most poisonous part of a black walnut, with the nut husks following, and the roots can poison other plants that grow under or near the tree).

There are black walnut trees all over Virginia, even one in my own yard (its well away from where my horses will be, though) I will not be overly concerned about it. Most of the danger is from walnut shavings or from standing under walnut trees for long periods. Generally, horses won't eat the leaves, nuts, or bark, and I don't blame them, its really nasty-smelling. Oh, yeah, and it doesn't burn for poop! neither do the nuts. we wacked our tree back last year and tried to burn the brush, and the walnut branches and nuts would take 3 or 4 burnings to be consumed.

The question:

It has long been established that Black Walnut (tree) is very toxic to
the horse, in any form (leaves, shavings, etc.) I cannot find through
web searches, and local cooperative extensions, and Cornell, whether
or not other species of walnut are also toxic to the horse, like
English walnut. Have Carpathian English walnut on my property (and
horses). Really need to know.

The answer (s):

Subject: Re: Horses and Toxic Plants
Answered By: tutuzdad-ga on 06 Aug 2005 16:33 PDT
Rated:5 out of 5 stars

Dear paxvobiscum-ga;

Thank you for allowing me an opportunity to answer your interesting question.

The toxic phenolic compound in Black Walnut is called "Juglone" (5
hydroxy-1, 4 napthoquinone). It is found in the bark, wood, nuts, and
roots of black walnut (Juglans nigra). Most members of the Walnut
family (Juglandaceae) produce this chemical including Black walnut,
pecan, hickory and others members of the family including Carya,
Engelhardtia, Juglans, Platycarya and Pterocarya. Black walnut and
butternut produce so much of the compound that plants growing nearby
can become poisonous just by glowing in the vicinity of the tree.
Other species including English walnut, pecan,
shellbark/shagbark/bitternut hickory, produce such small quantities of
juglone that toxic reactions in other plants are rarely observed.
Black walnut is the most toxic but these other plants still pose some
direct risk to horses as well.

I hope you find that my research exceeds your expectations. If you
have any questions about my research please post a clarification
request prior to rating the answer. Otherwise, I welcome your rating
and your final comments and I look forward to working with you again
in the near future. Thank you for bringing your question to us.

Best regards;
Tutuzdad – Google Answers Researcher


Recommended reading:



UNIVERSITY OF IDAHO'Carpathian%20English%20walnut%20j uglone'










Clarification of Answer by tutuzdad-ga on 07 Aug 2005 11:26 PDT

Thank you for the generous tip!

[Tutu says "Hey back atcha"]


paxvobiscum-ga rated this answer:5 out of 5 stars and gave an additional tip of: $4.50

tutuzdad - thanks. I get from reading all the links, that ASSUMING
that horses in close proximity to the Carpathian are all right, is
unwise, especially due to the spread of the root systems possibly
affecting nearby growth, and to the fact that the horses can't be
protected at all from possible effects of pollen drift.

The gorgeous trees must go. However, references to rotting root
systems after trees cut down, may not hold water either. Lost a
mature tree to mini-tornado, then it regrew from old root system.
Horses ate leaves of new growth, killed the young tree, and now it is
AGAIN regrowing.

Another VERY mature tree, had no leaves for two seasons (late frost
problem). That same tree this year, put out about 1/3 of full set of
leaves. They basically refuse to die, probably BECAUSE of the extent
of the root systems. May have rather large problem trying to
eradicate. You folks knocked me off the fence on this one. Had hoped
could let trees live. Am buying field guide you folks suggested, as

Say hi to "tutu" for me.

I am most impressed with the help I got from you, and the helpful
"commenters" on Google Answer. Will definitely use this service

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Subject: Re: Horses and Toxic Plants
From: omnivorous-ga on 06 Aug 2005 07:34 PDT

Pax --

It appears that the risk is with black walnut trees and shavings (the
latter sometimes finding its way into bedding). Agriculture Canada
only lists the black walnut as toxic:

Agriculture Canada
"All Poisonous Plants"

The active element in black walnut is a growth inhibitor called "juglone".

Meadowsweet Acre Herbs (Google cached link -- live link was dead early on Aug. 6)

You might want to check with an arborist to see if your Carpathian
English walnut trees have any significant amount of juglone.

Best regards,


Subject: Re: Horses and Toxic Plants
From: hagan-ga on 06 Aug 2005 08:03 PDT

My research mostly tracks with Omni's:

"Other trees closely related to black walnut also produce juglone,
including butternut, English walnut, pecan, shagbark hickory, and
bitternut hickory. However, all produce such limited quantities
compared to the black walnut that toxicity to other plants is rarely

Carpathian walnuts are just cold-hardy strains of Persian, or English,
walnuts (Juglans regia L.), and are in the Section Juglans of the
species Juglans.
Black walnuts are in the Section Rhysocaryon of the species Juglans.
They are a different genus from the English walnuts.

Caution, however: English walnuts are often grafted onto black walnut
rootstocks, and it is unclear whether that would affect the leaves of
the English walnut:

This site (a newsletter put out by the Valley Horse Owners Association
in California’s San Fernando Valley) states that English walnuts ARE
toxic to horses. But since it does NOT mention black walnuts, I
wonder whether the newsletter was confusing English walnuts with
black. There is a picture of the plant they warn against, so you
might want to take a look:

This site (discussion forum) includes a comment by a person who states
that she has had her horses in pasture with English Walnuts for 9
years with no problems, even when the horses eat the leaves; but she
does take the horses off that pasture when the nuts fall, just as a

None of this was definitive enough for me to post as an Answer, so
perhaps someone more knowledgeable will come along and add to what
Omni and I have learned. Good luck!

Subject: Re: Horses and Toxic Plants
From: paxvobiscum-ga on 06 Aug 2005 08:35 PDT

Thanks for the help. Sounds like the answer is "MAYBE". Frustrating.
Perhaps there is not a definitive answer at this time, but after
having read some of the material in the links, I guess I wouldn't want
them injecting horses with the questionable substance, just to see if
something happens.

Thanks much Omni and Hagan. From here, will try to find out about the
root stock on my particular trees before I cut them down.

Subject: Re: Horses and Toxic Plants
From: kriswrite-ga on 06 Aug 2005 13:57 PDT

The difficulty with this question is that it's tough to prove a
negative. It is unlikely that if other kinds of walnuts are toxic to
horses that literature would mention this. The focus of the sort of
literature that will be helpful to you is to point out plants that ARE
toxic plants. (For example, see "Toxic Plants in Your Horse Pasture:" )

What I would recommend is that you get a good book on toxic plants and
horses. Here are two recommendations:

* 'Horse Owner's Field Guide to Toxic Plants,"

* "A Guide to Poisonous Plants for Horses,"

If I were in your position, I would buy the first book.

I hope this helps,

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Old 05-11-2006, 05:11 AM   #4
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I had always heard that it was the black walnut only too Face.
The other walnut and pecan trees-it says also have the toxic agent-in small quantities. Those dang pecan trees are all over texas and we have never had an issue at all. Even with some of the horses who like to worry off the rinds and eat the pecans! silly buggers
Check with your local county Extension agent. They are a great source of info on local conditions and problems.
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Old 05-11-2006, 08:28 AM   #5
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WOW. You sure came up with alot of info! From what you've provided I think maybe we'll just try and find another place for the darn tree. Thanks so much for all your help!
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Old 05-11-2006, 09:57 AM   #6
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Old 05-12-2006, 07:22 PM   #7
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Boy isn't that the truth about things to worry about. I've had a number of pastures over the years that had buttercups (not alot) and the horses won't eat them as long as there's decent grass in there.
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