tonya,
I'm a veterinarian, and I'd never heard this one before, but a Google search indicates that moldy walnut hulls may indeed pose a hazard. However, after being involved in veterinary medicine for nearly 25 years in areas where black walnuts are a common and significant part of the climax canopy and occasionallly in the urban landscape, the fact that I've never seen or even heard of this phenomenon, I'm somewhat inclined to think that the threat is pretty minimal - though, if it happens to your own dog, it's very important. I've always been more concerned about an overzealous pup swallowing a black walnut whole and ending up with a gastrointestinal blockage.
It's pretty difficult, and certainly impractical, to attempt to prevent a mature black walnut from producing nuts - that's what they do. If it's even possible, it would probably require yearly applications of Florel at the time of bloom. Your realistic options are to: pick up all nuts as soon as they drop from the tree, have the tree removed and plant something else, or just watch your dogs for any inclination to chew on the nuts.

LOL. I have four black walnuts, a dog and no problems.

Thanks for the input everyone. My husband came in and told me that the dogs have learned to crack open the nuts to eat the inside. I think we will have to plan on picking up the nuts as they fall. I'm so looking forward to that! :-) LuckyP, we've recently moved to salt lake city and apparently they don't have squirrels here in the suburbs. I've asked around and they only live in the mountains. Imagine that. I guess our bird feeders are safe!! (or we could smuggle some in...)

My Rotti has recently been having seizures. After several costly vet visits, we've determined that it must be the black walnuts. We've ruled out everything else except tumors (the next visit). She's too old for the onset of epilipsy. I've only found a few references to the toxicity of these nuts and they mostly refer to birds or horses. In the meantime, we'll be removing the nuts from the ground and should we determine that this is causing her seizures, the trees will be removed. My suggestion is to keep an eye on the dog to make sure they're not eating the walnuts. Better safe than sorry as they say

Is the dog passing walnuts or walnut hulls in the stool? What are you feeding the dog? Like Lucky P said this seems like a reach to me.

I had a standard dachshund that ate every walnut he could find. The main problem was not toxicity, but obesity!

I have a black walnut in my backyard and a nearly 3-year old Chocolate Lab. The dog has no history of seizures but recently had 2 of them in the last month (one mild, one severe). I found the post about the Rottie having seizures interesting - and was hoping that the person who posted is (susaninnc) was still monitoring this thread 2 years later. If so - I'm wonering if the seizures stopped after the nuts were picked up and/or the tree was removed. The good news is, the tree is on Baltimore City property and was recently flagged to be removed by the City because it's falling over anyway. The bad news is ... government moves slow ... and I have no right to cut it down given it's not on my property (but hangs over it - REALLY high up). The squirrels eat the nuts and shed the husks all over my lawn and yard - and the dog can't stay away from the husk pieces. My Google search suggested the issue isn't the nut - but a fungus or mold in the husk. If that's true - I'm wondering what the affect of that mold/fungus would be on the dog. Would it act like a neuro-toxin and potentially cause seizures? Would it stand to reason that a kidney enzyme might be elevated as a result of that (her kidney enzyme WAS elevated after the severe seizure, but not 1 week earlier when she had a blood screen prior to a teeth cleaning).

Thanks ahead of time to anybody who may be able to shed some light on this ... we're obviously concerned.

FYI - I just found the link below on the ASPCA website suggesting that black walnuts and husks do, indeed, cause tremors and seizures in dogs. I'm now even more curious than ever about what happened with the Rottie - and what the Vets on this thread think about this report. I clearly don't take everything I read on the internet as the truth - but something posted on the ASPCA site I'd lean towards believing. Vets - are there other sites I can research this further with - or are there specific questions/tests you could recommend I talk to my vet about so we could see if this was, in fact, the cause of the seizures in my Choco Lab?

Thanks again ... and sorry for the quick re-post. I found the ASPCA site minutes after posting my original reply above.

Here is a link that might be useful: ASPCA Poison Control - Black Walnut

My peekapoo had seizures about 4-5 times a year and we had a walnut tree in our backyard. We recently moved to a new house with no walnut tree, and he has yet to have a seizure. I am convinced it was the walnut tree.

Huh. My neighbor has had 3 dogs and has 3 black walnuts and over the 13 years I have lived there none of his dogs has had a seizure. Guess they just don't eat the walnuts or something. I have a dozen or so walnuts but no dogs.

My black lab would attack the green walnuts when they fell from the tree. He would play with and chew on them till he foamed at the mouth. One day he started acting funny and had trouble walking. I took him to the vet and mentioned his walnut chewing habit. After blood work, the vet said "a few more walnuts will kill him!" He said his blood was full of toxins! When I expressed surprise at this, he told me that as a boy back in the 40's, he would fill a potato sack with the green hulls and throw them in the nearby creek and after a while pick up the stunned fish that floated up!

I had a walnut tree for years that belonged to a neighbor but dropped nuts into my yard. My collie never had even a passing interest in eating the nuts. However it all depends on how interested a dog is. It sounds like it could be a real danger if your dog likes to eat them or chew on them.

I have heard for years that black walnut shavings are a hazardous bedding material for horses. I never used them (or any other bedding either, since my horses had a run-in shed that required no bedding) but I don't doubt that they can be poisonous.

i know that the black walnut hull can be used medicinally as a dewormer...so if SHTF and you got some parasites go chew on some black walnut hulls

When the nuts are green and fresh, if a dog picks it up or chews on it...they will vomit... a lot. Then never do so again. BUt the older nuts without the green shell are a different story. And yes, I Had a friend whose dog died from eating old moldy walnuts, or walnut shells. I think when the nuts are dried and not moldy they are not poisonous . I hate to,cut down these huge trees, and I found some walnut and apple picker uppers online. If for the walnuts buy the smaller size, even if they recommend the larger, ...kind of a rolling cage thing. They work!!

i have seen the cows eat a few English walnut leaves and be okay, but my neighbors sheep have eaten poisonous plants and die....often!! He doesn't seem to pay attention to,the trees and plants he has growing and will give them when cleaning up.

I don't dispute the evidence that black walnuts can and occasionally do cause these issues in dogs. But I must say, it can't be commonplace. My son- dog owner from forever-has lived many years now in SE Wisconsin, a land heavy in black walnut trees, including both his present property and the one before that. So I don't think it's universal problem. Still....worth looking into.

They are toxic to dogs if moldy. Most dogs don't chew on them or spit them out because of the taste. Some dogs will chew anything especially if excited including rocks. It can take 2-5 days for it to leave the system but I found an activated charcoal capsule speeds it up a bit. All of my dogs have left them alone for over 10yrs until my new adoption. Showed neurological signs and lack of muscle coordination about 5 hours after chewing one and swallowing small black flakes.

Started getting progressively better after 24 hours and lasted 3 days before back to normal energy levels/behavior. Noticed lack of energy very slowed movement, air licking, trouble bordering on refusal to going up or down stairs or furniture. If it wasn't a young 75lb dog seizures or worse would have been likely in my opinion. I had no idea they were toxic but my neighbor, who is a retired vet, confirmed and said symptoms were similar or worse for horses.

Every year when black walnuts start falling, my dog will find one & chew on the green hull before we can take it from him. He gets "sick as a dog" as the old saying goes. He gets so sick afterwards, nausea & vomiting! He plays with them like they're balls, he's so happy when he manages to sneak & find one but I wish he'd remember just how sick he gets afterwards. Not fun for him or me..cleaning the house.

In case anyone ever has this problem and searches for this thread:

our dog is 8 and never had a problem with our black walnut tree. Never chewed on the husks/nuts. However, today we had it cut down. Our pup ate some of the fresh sawdust and 2 hours later had problems walking. He is currently in the ER vet for the night, getting medicine and IV fluids.

so if you do remove your black walnut and you have a dog, clean up the sawdust before you let your dog in the yard.

ps cutting down the tree (and another tree next to it: $1400

The resulting vet bill: $2600

Gun stock makers will pay hundreds of dollars for black walnut wood, including that from inside stumps and large roots. And will extract it themselves.

The green hulls will absolutely make your dog sick, vomiting, diarrhea, lethargic. The squirrels are bring them into our yard and our dogs keep getting to them. It’s awful trying to comb our yard trying to pick up all the pieces.

We grew around walnuts and dogs carry them in their mouths and nothing ever happend. What we know is that their a history of black walnuts poison parts. But no article tells you is how much needs invested. Growing up with arborist in the family we were told that most of toxin is in the roots, then the husks. Their is a much smaller amount in the branches and leaves. Our one dog picked one up once and dropped it must have tasted crappy I know they smell bad. So I think I wouldn't be worried by one small thing but more so maybe with volume. Each dogs system is different just like ours.