What is in Black Walnuts that is bad for roses?

I'm curious, because out at Rancho Camulos in Southern CA, there is a massive old Black Walnut -- more than 100 years old, I think, and huge. I knew B.W.s had termite problems, but I did not know about toxins.
Curiously, there are beds of roses to both the East and the West sides of the area where the big black walnut grows, and they seem never to have been affected by anything.

The Camulos Web Site says of that Black Walnut:
California Black Walnut Tree
"Of special interest is the California Black Walnut Tree, "El Rey Nogal," the only survivor of four "Black Eagle" seedlings planted by Juventino del Valle sometime during the 1860s. The tree has been noted by Maunsell Van Rensselaer in his publication Trees of Santa Barbara as the "Camulos Black Walnut." The author noted that it might be largest California Black Walnut in the region. When it was measured for this book in 1940, its circumference was eighteen feet with a branch spread of 129 feet. Today, the trunk measures approximately twenty-five feet in circumference with a branch span of approximately half an acre."

Jeri

Since I am surrounded by BW trees (about 9), I have made a career of exploring the various levels of tolerance. First, let me say that I don't believe these trees belong in the home landscape-they are messy (lose leaves and branches year around) are the first to drop leaves in late summer early fall and the last to leaf out in the spring (an advantage to deciduous plants who like winter sun-like roses). The walnuts are a health hazard once they start dropping because they are extremely oily and slippery (they hurt if they hit your head,too. If you are looking to harvest the nuts, be sure you have the right equipment to crack the nuts. The shells are super hard and a hammer will not do the job. In addition to the leaves and nuts, be sure you clean up the buds. These are extremely toxic.

About 5 years ago, I planted own root and grafted roses beneath BW trees. The level of toxins must have been very high because I have since moved or lost most of the roses. Like you, I started with multiflora hybrids or multiflora decendants, a lot of HMs, Veilchenblau, Russelliana, and Rugosas. Forget the chinas or any with heavy china parentage. Veilchenblau and Lavendar Lassie remain within the root zone (the most toxic part) and both are shadows of their former selves. A cutting of Veil. was rooted by my friend about 3 years ago and it thrives in her garden. In mine it will be shovel prunned next spring along with LL (about 6 " tall, down from about 4 feet).

With all this nay saying, you will be surprised to hear me say "go for it". Every garden is different and soils differ, care differs, climate differs. You never know. Plus Ann has had great success with her roses. She also has fewer BW trees.

I have discovered that the further the roses are from the tree the healthier they are. (DUH!) Those that are closest to the tree suffer, some slowly. It may take years for a full decline. Also, multiflora grafts work better than multiflora hybrids, own root. Russilliana (own root)was planted in my test plot and started a very slow decline. I moved her last spring, cut her back as little as possible and she bloomed surprisingly well and has nearly doubled her height in one season. This was a rose that had started off gang busters 5 years ago and slowly declined every year.

Also, at planting and every year thereafter, add copius amounts of organic matter to your site. The organic matter helps break down the toxins. I have attached an article that somewhat compiles various studies and gives some interesting information. Tolerance BTW is relative.

Good luck!
Barbara aka Hawkeye Belle

Here is a link that might be useful: Black Walnut Toxicity Explored

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And just so you can see, these roses are planted about 25 feet from my neighbor's BW. Golden Wings is on multiflora root stock. The rugosas are own root. This has not been the story on the other side of the yard where my experimental planting of hybrid musks and multiflora hybrids were planted. There the numbers of trees increase to about 5, spread out along the border. Those were the ones I moved.
Barbara

Well, WE would sure be in trouble!
Multifloras don't grow here worth snot.
Good job we don't have any BWs here!

Jeri

and we have found the hard wood of our Black Walnuts so so very much fun to cut, especially reaching awkwardly on a steep hill......

Walnut is a precious wood. A mature black walnut is worth several thousand dollars in lumber. There have been instances of people stealing them.

Yes, the trees are valuable lumber--even the few branches we cut once were quicky snapped up by neighbors for gun stocks. I have succeeded with rosa mulligani very close to the trunk, chevy chase a bit farther away, and on the edge of the drip line but far enough away not to suffer from the dry soil beneath the tree several gallicas have managed to do okay. Interesingly in regard to other sorts of plants it seems to be easier for those that tolerate alkali soils (lettuce, larkspur, some bearded iris and such) than it is for other plants.
But the trees are a genuine nuisance and shouldn't be placed anywhere near the house. We, alas, have to live with ours because it screens us from the road and because it is so huge that we would be dealing with the immense roots long after the tree was eliminated. The walnuts land on our car like cannon shot.

Yes, the core wood is valuable, but no so much as it use to be. The Federal Government got involved to keep the wood from leaving the country. The price is somehow controlled; I'm not sure of the details. I was told by a landscaper that is the case. I tried to give my trees away to a lumber yard and they would not take them. Also the circumference of the trees must be HUGE to get big enough core wood to cut lumber. The wood is undoubtedly beautiful!

Barbara

Thanks, that is Very interesting, Barbara! Are there also redwood restrictions from leaving the country? And euculyptus?

Back to Donna, I'm no help, none of my roses are near my BW's but you got me to stop and rethink my planting project I'm doing right now. I have been uprooting roses and moving them down below in the pasture, where I wanted them originally, never mind, that's another story. There are some I have with intent near one Walnut in particular. I have pictured a Darlow's Enigma at each end of a retaining wall behind a BW and a White Lady Banksia in the middle. Also a Mermaid down a bit from another Walnut, outside of it's drip line. I wonder how close is too close?
May I add, I would not think to remove my Black Walnut trees any more than I would want to part with my big old Oak tree. They are graceful beauties and gratefully in the pasture where not concidered a mess.
I have heard of netting an upside down umbrella shape under the trees to funnel the nuts into a basket, collect and protect in one. Never tried. And I don't have concrete below to know, do the leaves cause any staining?
Hope your project ends well Donna.

Bodica,
I don't know about other trees or restrictions that may or may not be attached. Sorry.

Barbara