Well, this question has been hanging out here for a while with no responses. I am dissappointed because as a Norway spruce lover I would like to know.

There was an earlier topic here about white pine and black walnut, and one of the responses said that yes, white pine was affected. The only thought I have is, and maybe it is a question, if one member of a plant family is susceptible, is it probable that others are also? Of course Norway spuce and white pine are both members of the family Pinaceae.

Also, your spruce are 50 feet away? Is that far enough? I know Norway spruce roots can go a surprizingly long way, but I don't know much about the root spread of black walnut. but at least some of the spruce roots will be in soil unaffected. So what if half of the roots overlap--does that reduce the effect of the juglone? How much?

Well, I hope thee are some experts that can chime in here. It is something that I never thought about. I will certainly look for evidence. There are a lot of black walnut and Norway spruce in the area. I will look for them growing together.

--Spruce

My juglone question arose while I was looking for deciduous trees to plant around the yard. All of the sources I've found indicate that White Pines are sensitive to juglone, yet in my yard I have multiple white pines growing within 20 feet of black walnuts. White Pine #1 is only 5 feet away from a black walnut! The Noway spruce pictured is 40-50 feet away from the nearest walnut and is growing like bonkers. All of the trees in the picture (except the NS) were planted at the same time about 25 years ago. The current sparseness in the pines can be attributed to overcrowding, and this decline only began about 5 years ago. The tops of the trees are still dense and prolific.

All of the NS I planted this year are just to the left (south) of the picture in an open area created by clearcutting scotch pines several years ago.

What bothers me particularily, thinking back to when I planted a few weeks ago, is that I severed several walnut roots when digging the holes (the smell can't be mistaken). This was before I knew about juglone. Guess I can only cross my fingers at this point...

I have no problem with any of my conifers growing with in 25 ft of Black Walnuts.

Dave

I've been in this house approxmately three summers. The property is ringed with Walnuts. I have White Spruce and Norway Spruce, planted before I arrived, thriving in close proximaty to the Walnuts. My favorite information about Black Walnuts is on the Cornell University Cooperative Extension website; however, I have discovered that it is all a crapshoot because most of the evidence is "observed" and there are so many variables. I have observed a White Spruce growing directly under a huge Walnut and thriving. My bet is that your Norways will be fine.

Just to add to the confusion. I have 8-10 Walnuts >100 feet on the property. There were white pines within 25 feet that slowly died.

There is a white pine about 40-50 feet away from the Walnuts that is > 100 feet tall.

In the back yard there are several Norway Spruce > 100 feet tall within 50-75 feet of the Walnut

I agree w/ variables theory. Our prev house was in a turn of the century neighborhod, w/ many walnut trees planted only 100 years ago for future profit. Dirt was alkaline topsoil on clay w/ sandbar below (=great drainage & roots grew down deep). Alot of plants grew that weren't considered tolerant. Now we're 8 blocks west in a former native walnut & raspberry grove w/ high water table & acid soil, and the juglone effect is so much more pronounced. Logically, current dirt was created by hundreds of years of accumulated walnut branches, leaves & decomposed roots.

Two anecdotes: neighbors have a 80' spruce in their backyard 25' from younger mid-size Walnut tree. Branches on Spruce slowly dying, but only on side of tree that perfectly faces the walnut. They hired a tree "expert" who tested pH, measured moisture, trimmed dead limbs, has no idea why dying. Each year as Walnut gets bigger, Spruce dies alittle more...
Was talking to different neighbor about Juglone/Pine issue - he'd never heard of it, but was happy to learn why White Pine & Spruce he planted next to Walnut only grew 3 ft in >15 yrs.

No experience with Norway Spruce near Black Walnuts, but I am going to try. We have found Black Walnut roots nearly 75 feet from the trunk invading my foundation beds. I now understand why birch trees and rhodies have not done well there. Hosta and Holly seem to thrive. We excavated the beds incl. the walnut roots! down 15 inches and replaced the soil. Hopin and wishin it helps.

My observations are that Norway spruce in this 30 year old plantation have shown little if any damage from the numerous Black walnut invasions...The walnuts do have a nice clean bole free of limbs for a considerable height!

Here is a link that might be useful:

Interesting! thanks for the information, guys. After this topic was first posted, I did a web search, and found only contradictory information.

I am wondering if this juglone tolerance is not a relative thing, which would explain the contradictory information out there.

Could it be that NS is relatively tolerant, but not unaffected? Growth and vigor may be affected to some degree, but not severely. I think what we need are some controlled experiments to determine whether there is any substantial effect or not. I have no observations to contribute, but am very interested.

At my new place near Winchester, VA, I have planted a very long NS screen/allee. There will be some walnuts close to this screen, but, maybe not close enough to give good information about tolerance. To tell the truth. I have been wary of planting the walnuts very close. I wish I really knew what the effect would really be.

--Spruce

I am convinced that young Norway spruces cannot coexist with mature black walnuts. In the area shown in the above photo, I have replanted most of my NS transplants 2 or three times. I finally had enough, and early this spring I removed the walnuts, and also replaced the soil in the planting holes with soil from another part of the yard, but of the same general quality.

It was amazing what the roots of the walnuts looked like that were dug out of the old transplant holes. 1/4" diameter walnut roots which were severed at the edge of the hole the prior year had produced a vigorous mat of fibrous roots from the cut which filled the hole in which the NS was planted in! I wish I had taken a picture of this, I could not believe it.

The NS that were in these holes survived and prospered for the first month or so after transplant, but by the beginning of July all growth stopped and only very tiny or no buds developed. By the time the soil started to thaw this spring, the needles turned brown and fell off. I am convinced that this rapid decline is due to the walnut roots so quickly re-invading the transplant hole.

While it is still early June, the new NS transplants that were planted in the replacement soil this April are putting on much more growth than their counterparts from the prior years.

I treated the walnut stumps with Tordon immediately after cutting and they have not resprouted.

I want to add a final thought to my previous post. A storm was imminent and I had to shut down the computer...

I do have a couple of NS within the walnut root zone which have survived the past few years and are now prospering. I think this is possible because these trees were planted where no walnut roots exist. I suppose the farther away from the trunk you go, the farther spaced apart the roots of the walnut tree are. It's a matter of luck. If I had to propose a theory, it would be that if you dig a hole to plant a NS, and you sever a root of a mature black walnut in the process (they are easy to identify by the smell), the NS is not likely to survive.

One thought that may shed some light on this subject.
Soil type,I read in at least one publication on the effects of juglone.They stated that the heavier your soil the more likely juglone would build up in the soil.
I have a sandy loam with a gravel base,this might be the reason I don't see much of the symptoms of juglone.

lp

I don't believe juglone can "build up" in the soil, unless it is because there is more root mass in that soil. Juglone breaks down quite readily once the bark, root, leave, or whatever is separated from the tree. Composting breaks it down, even sitting in the open air breaks it down. FWIW, an NS seedling that sprouted in my yard under the canopy of a neighbor's Black Walnut grew quite well to about 4 feet before it was getting too big for it's spot. It was transplanted to my brother's yard where it grows still.

tj

I have a blue spruce that is turning brown on one side. I’d like to mulch it good to conserve water and reduce weed Competition. I have a mulch pile that the electric company dumped for me from tree trimmings of the neighborhood. There is a possibility of black walnut in the mulch. Does anyone have an opinion if it’s safe to use?

As a mulch around trees it will be fine.

tj