Take some advice, Cut those Black Walnuts down. They are the bain of gardeners everywhere. Possibly small enough now not to cause problems, but wait till they're bigger.
When they start to 'fruit' they'll attract squirrels from miles away, which then start to bury the green nuts in your dug garden. These then rot causing all sorts of problems for your plants. If you try to grow beneath the drip line, more problems, and the roots also suck up water like you wouldn't believe.
The drip line has killed an old Mackintosh in my garden. Get rid of them is my advice.

They will kill your apple trees period. I am going through the process myself as 45% of my orchard (the part that was cleared last year) had BW. 12 of 17 new trees died. Both cherries, 1 peach out of three, both asian pears, and 7 apples out of ten died.

Remedies include cutting the BW, trenching between BW and orchard to sever roots, and tilling in lots of organic matter. You could also plant new trees in the trench, and if they resist BW, they will eventually form a barrier that stops further propagation of roots. If the trees are difficult to take down, a little girdling will not kill them outright but will compromise their ability to produce juglone.

I have also put down a good amount of fungus spawn. Juglone decays very quickly in good soil, its lifetime in contact with common bacteria and fungi is measured in hours or days. But there has to be contact, in a compacted soil which is difficult to penetrate it can persist for years.

They kill everything basically that grows near them.I had 5 huge trees here in the yard when we moved here hate them...

Ohio Walnut info

Basically, walnuts are allelopathic to many species. Of course, some people - like me - grow them because we eat them. I have about 50 acres of black walnut trees planted for the dual purpose of producing trees and nuts.

DarJones

I have often seen and even managed fruit trees, especially apples, living productively in the vicinity of black walnut trees, but I agree that it is best to cut them down near orchards. Peaches seem to suffer the most, in my experience- but peaches suffer the most from any large tree competition.

Also, I have found blueberries to be impossible to grow anywhere near black walnuts.

CP, problem is, most have limited space.

You dont HAVE to use trees for that purpose. Using smaller plants will achieve the same general results. ALso, Im assuming that the OP has a decent sized yard, it seems like he has a double lot at a minimum.

Once has to think as well, those walnuts may be helping keep "invasive" or "weedy" plants from taking over, due to the jugalone and shade. Im more or less saying that there are more options then just "cutting it down", which is too often recommended IMO.

Bottom line, it is fruit trees or BW, not both. In the ticket bordering my orchard, there are only BW (3), aronia, and another spiny, shrubby tree I could not identify. I don't see the diversity there, specially considering our area is dominated by hickory and oak, which are absent (I will plant some this spring, because red oak is resistant).

I cut down the BW closest to the orchard, and girdled the other two (they are not large, 5 to 9 inches diameters).
They will kill at 70 ft distance, as it happens with the very large BW in front of my house, whose roots reach the gutters of my home. Starting from scratch, and knowing where they are, I tend to agree that trenching, plus a bamboo barrier, plus a living barrier such as Eleagnus or hybrid willow, plus tilling in of a lot of manure, will work.

And it is not just fruit trees. In the lanes I can not grow most vegetables. I planted asparagus around the perimeter and those plants on the BW side are all dead.

"Starting from scratch, and knowing where they are, I tend to agree that trenching, plus a bamboo barrier, plus a living barrier such as Eleagnus or hybrid willow, plus tilling in of a lot of manure, will work."

That is a great point I neglected to remember. Thanks.

Here are a few more links listing tolerant plants:

https://www.extension.iastate.edu/news/2005/jul/070701.htm

http://hort.uwex.edu/articles/black-walnut-toxicity

Hi Jean,

I have many black walnuts on my property. 4 years ago, I cleared an area to plant my orchard. Cut trees, ground stumps, and replanted. Most of my 50+ bareroots are entering their 3rd season. The orchard is still bordered by black walnuts, some very mature, as close as 50'. Up to this point, I have seen no ill effect. I do see on some areas of my property, grass won't even grow within a couple feet, other areas they cohabitate fine with many things. I am curious to see how last years blueberry plantings will fare.

Chad

Juglone decays fast if the soil is very bio-active. Can you see a correlation between number of worms in the soil and other species tolerance of BW? In my orchard soil there are surely very few worms.

In the last few years we have been adding copious amounts of compost and spraying ACT. It has made a difference to the worm count, our general garden is better, stuff is growing better.
So I do believe bio-activity does minimize the effect of BW trees.

"Juglone decays fast if the soil is very bio-active. Can you see a correlation between number of worms in the soil and other species tolerance of BW? In my orchard soil there are surely very few worms."

"In the last few years we have been adding copious amounts of compost and spraying ACT. It has made a difference to the worm count, our general garden is better, stuff is growing better.
So I do believe bio-activity does minimize the effect of BW trees."

In most people orchards this is a rock and a hard place. Generally, soil organisms dont like the fert and chemicals we spray on our orchards, and the mycorrhizal fungi even less so. So how do you create "bioactive" soil, when most people are urged to spray, or the trees need to be sprayed to survive long term?

You want it bio-active in the beginning, when the trees are growing and the juglone is present. Later, if you stop bringing in wood chips, the bio activity will go down.

"In most people orchards this is a rock and a hard place. Generally, soil organisms dont like the fert and chemicals we spray on our orchards, and the mycorrhizal fungi even less so. So how do you create "bioactive" soil, when most people are urged to spray, or the trees need to be sprayed to survive long term?"

Canadian,

I like to build healthy soil. Although not as critical for fruit trees, there is something that makes me feel good knowing the soil is healthy and fertile. Maybe it's a psychological thing.

That said, I don't think it's that difficult to maintain a bioactive soil using both compost and sprays. Of course it depends on the particular compound used, as some sprays are more earthworm or mycorrhizal friendly than others, but I find it's a sort of "if you build it they will come" phenomena. There is so much food/decaying matter the soil maintains a rich diversity of soil life. Although some pesticides can kill the soil organisms, from my experience soil food seems to be the most limiting factor for soil life.

I try to avoid any unnecessary sprays but still end up spraying a fair amount because I live in a humid climate with a lot of insect/disease pressure. Additionally I sell fruit which carries a higher standard for appearance.

From a herbicide standpoint, I try to keep the trees mulched with wood chips which cuts down on herbicide use considerably, but doesn't eliminate it.

In my soil I normally see tons of earthworms in the top 6". The exception was last summer when it was so bone dry. That seemed to decimate the earthworm population.

I've not tried to measure mycorrhizal colonization, but can tell you the soil smells good. There are all kinds of little creatures crawling in it, so I suspect mycorrhizal populations are high.

I don't use chemical fertilizer because I think it's unnecessary in most soils where organic mulches are regularly used (The mulch adds plenty of fertility.)

I think you may have a point for many commercial orchards. They don't use mulches and do a lot of spraying. Certainly many of these soils lack organic matter, although fruit trees don't seem to need it as much as other crops.

CP, the only chemicals I believe have proven detrimental to mychorizal relationships is nitrogen and phosphorous- especially P no matter the source. If your assertion is science based please direct me to either research or a research based institution that has any information to support your rather broad assertion.

I could live on the earth worms in my soil that live under sprayed trees of my orchard and the land and soil are full of a wide diversity of insects, plants, birds and so on. For about 4 weeks of the growing season there is poison on the trees. The stuff that lands on the ground biodegrades very rapidly.

HM, so if one manures the hell out of his garden, at some point mychorrizae start disappearing? What about orchards (or gardens) started on land that was long a standard lawn (therefore fertilized yearly with 10-10-10)?

Glib, please read what he/me posted again. We are talking about chemicals, as in petroleum based fert. or sprays. And in theory, yes, too much nitrogen can burn plants if im not mistaken.

Harvestman

Give me a day or 2 because i need to go through some books, but yes, the source is credible.

He said no matter the source of P. Did he mean no matter the inorganic, chemical source of P?

It's been a while since I last delved into the research on mychorizal fungus but as I recall the trees themselves must cooperate to some extent in this symbiosis and the main benefit they get is access to phosphorous in soils where it is otherwise deficient. If there is ample P the interaction is reduced greatly on both sides.

My recollection is of questionable value on this, however- memory is a use it or lose it proposition for me.

I do believe the mycorrhizal networks do something with starches as well. What you said is the same as my memory provides in regards to P. Hopefully both our memories arent wrong :P

One of the books I was referencing was "mycelium rising". It mentioned that something like half - 3/4 of trees have/need some sort of sybiotic relationship with fungi.

In the time its going to take to go through these books, Im sure we can both agree chemicals dont improve soil life?

It is quite reasonable. The sugars given to the fungi cost energy, and the tree will do it only if the exchange is profitable. If so, there should be a water dependence as well, since water is the other main benefit for the tree. And indeed I note that a number of known mycorrhizal fungi thrive on dry slopes, most notably truffles and boletus (porcini) families (yes, my interests in these are not scientific).

The fungus gets carbos that either leak through roots or the fungus reaches by penetrating the roots- two distinctive relationships there that involve different groups of fungus.

These relationships are truly remarkable, potentially expanding the extent of a trees root reach many times. Interesting how trees micro-friends and enemies are primarily fungus while animals benefit and are attacked primarily by bacteria with virus a strong second on the enemies list.

Humans probably have more bacterial friends than enemies, considering that our skin, mouth, and gut are completely colonized with friendly bacteria. I have a pet theory that gardeners are healthier than non-gardeners, because we are exposed to lots of different soil bacteria that non-gardeners just don't contact anymore. Of course, it could be that we eat more fruits and vegetables, too. I'd love to research my theory someday, but I don't think I'm ready to go to back school for a PhD in Soil Sciience just yet.

Sorry I got off topic. I'm sure there are several plants that are tolerant of Black Walnut's juglone, but many fruit trees just aren't. And unless you really want the walnuts and are willing to give up the fruit trees, I'd vote to cut them down too. A weed is a plant that is growing where you don't want it, so for you, they're weeds!

I agree that a serious fruit gardener has enough to contend with without handicapping themselves by having chemical war waged against their trees in the soil. Also I believe that it is more than simply poisoning- established black walnuts are extremely competitive as their roots are extremely prolific in areas where they grow.

I have recently established an orchard in the vicinity of these trees and the density of black roots in the area is remarkable. I have the area around each individual tree spaded with a King of Spades type solid steel, long handled shovel just as BW's show signs of growth. So far so good, but I'm sure the roots will eventually go under depth of spade work. As usual, it is the peaches that have been most sluggish- they tend not to compete well against established trees when transplanted.

I've often thought that some kind of heavy fabric or copper screen set in the planting hole might be affective if it was part of the original installation.

A bamboo barrier and trencher, in fact, is what I suggested. It is very useful, as you note, to be able to distinguish BW roots from all other ones when digging. Yes, they are the blackest and easy to identify.

Going below bamboo barrier is a problem. No apple will survive long if there are BW roots 3 feet down. Probably the only cure one can try is to make a really large hole, and dump some large logs in there which have fungal activity (on inject with mulch that has shown activity). The log will be a large food base for a decade or so, and the mycelium will spread at depths your barrier won't reach. As you can see, much better to cut the BW, and let fungi destroy the roots starting from the stump. The roots will guide the mycelium to where the juglone is.

Glib, I have seen very old apple trees surviving in the vicinity of black walnut trees. I don't think you are correct in assuming lethal consequences and I believe I've even read of a list of apple varieties relatively resistant to them with Gravenstein as one.

There may be various factors at play that influence the severity of the problem from site to site. Where I installed that orchard there are 2 very old apples next to a couple very large black walnut trees (60 or 70'). Both apples are pretty healthy although their overall vigor may be reduced by either the juglione or just the straight out competition for water and nutrients. Roots of all trees are sharing the same soil right up to the trunks.