Questions on: Walnut

Ron Smith, Horticulturist, NDSU Extension Service


Q: I have a pair of walnut trees that are more than 17 years old. How does a walnut tree set fruit? These trees never have produced walnuts. (e-mail reference)

A: I assume you have black walnuts. You are close to the fruit-bearing stage of the trees, which is about 20 years. You might consider these fruitless years to be a blessing because every squirrel in the county will be doing the harvesting for you and then planting them wherever they wish once the trees start bearing walnuts!


Q: I am a faithful reader of your column. We have a problem with walnut trees. When we moved to our present home, the lot next door had small walnut trees in a windbreak. Our garden is adjacent to these trees. As the trees have grown, our garden is producing less and less. Someone told us that walnut trees emit a type of poison in the soil that prevents the growth of plants. The only plants that will grow are rhubarb and peas. Each year, as the trees get bigger, we are losing more and more of our garden. What is the solution? Please advise us before we talk to our neighbor about removing the trees. (Milbank, S.D.)

A: I seriously doubt that you will get your neighbor to remove some black walnut trees because they are too valuable. However, you do have some options. Locate the garden somewhere else if possible. Plant your garden in raised beds. This is easily done by taking 1-inch by 6-inch or 1- inch by 8-inch boards and placing them on edge. Then bring in some topsoil from another location away from the walnuts. Garden soil doesn't need to be much deeper than that. You can try container gardening. This is a fun way to grow vegetables, assuming you are not going after acres of them. Using containers, you can concentrate your tender loving care, and by using pasteurized potting soil, you wonít have to worry about weeds, diseases or soilborne insects. Walnut trees give off a substance known as juglone from the leaves and as an exudate from the root system. This is phytotoxic to other plant species that fall within the root system or canopy spread of the trees. Some species, such as the nightshade family, is more sensitive than others to this compound.


Q: Our neighbor gave us some black walnuts. He said all we had to do was put them in the ground and they'd produce a tree. This sounds too easy. Any thoughts on how to handle these nuts? (Turtle Lake, N.D.)

A: Your neighbor is correct. If you wish, you can break and peel off the husk and plant the walnut inside. That is too much work, though. Also, the stain you will get on your hands will last longer than black latex paint! Actually, the decaying husk on the nut helps soften the hard shell inside. Planting them now provides the necessary stratification for germination.


Q: I was given some black walnut seeds. I would like to learn how to propagate some of them. Do you have a bulletin that you can provide by e-mail or regular mail? (e-mail reference)

A: Sorry, we don't. You can allow Mother Nature to do the work for you by planting them about 6 inches deep this fall before freeze-up. The viable ones will show growth next spring, if the squirrels don't see you planting them and harvest them for food. These are difficult trees to transplant, due to their strong taproot development. I recommend planting the seed (for the most part) where you want the trees to grow. They take off fast in their youth and then produce slow to moderate growth as they enter maturity.


Q: I need some help with my black walnut tree. Four years ago, I planted it in memory of a dear friend. It always leafs out in the spring and has nice, healthy foliage. In a month or less, the leaves start getting brown spots, turn brittle and then die. I have tried different fungicides and herbicides, but nothing helps. Should I dig it up and start over? I really don't want to lose it, but it doesn't seem to be healthy. Also, it hasnít grown much. (Pingree, N.D.)

A: It is behaving like an Ohio buckeye and not a walnut. I don't know why it is doing this, so I suggest that you take it out and start over. Make sure itís planted at the right depth. Walnuts do not transplant easily, so you are better off starting over with a seed or seedling.


Q: I have a walnut tree question. My parents have a large black walnut tree that I used to play on as a child. For sentimental reasons, I would like to plant a tree from one of the walnuts. Is that possible? What do I need to do? If this is not possible, can I take a small shoot or branch from the tree and get it to grow as a seedling? (e-mail reference)

A: Growing from seed is the way to go. The biggest problem likely will be with squirrels in the neighborhood. They might be watching your planting activity and dig them up for themselves. This fall, pick up the nuts that drop to the ground. Wear gloves because the stain will be difficult to get off your hands for days, if not weeks, when you remove the green, outer husk. After removing the outer husk, plant the hard nut where you want the tree to grow. The winter temperatures will stratify the seed, so any viable seed will grow the following spring.


Q: I just read your answer in todayís column about nut trees in North Dakota. Are there any kinds of nut trees that will survive in western North Dakota? We live in a sheltered area. What varieties are the least likely to perish? (e-mail reference)

A: Black walnut would be good, but be sure the seed or plant source is from local stock, not from somewhere 200 miles south.


Q: I noticed your reply in the newspaper on how to crack walnuts. The crows have figured out how to do it the easy way. They drop them on the highway so cars run over and crush them and then they eat the pieces. Thought you would like to know how smart crows are. (Hendricks, Minn.)

A: Yet another way to crack a hard walnut shell! I used to have a small farm in my youth, attempting to grow berries and sweet corn, and have always been impressed with the crowsí intelligence. We should be studying their intelligence levels in addition to those of lab mice.


Q: I noticed your article about how to crack black walnuts. I used to live in Ortonville, which is just across the state line from Big Stone. For 60 years I have cracked my black walnuts using a vise. It works great! You can crack and re crack to get the meat out. I agree that they are good in cookies and fudge. Black walnuts are few and far between up here. I used to get mine from the Twin Cities but my supply source has dried up. (Moorhead, Minn.)

A: Thanks for your tip on cracking black walnuts. I resisted the temptation to suggest placing them on a concrete driveway and backing over them with a pickup that has steel belted tires inflated to the maximum. Any way one can get at the nutmeat is worth it! I'll certainly let you and everyone else know if a new supply source comes to my attention.


Q: I would appreciate information on how to crack open walnuts. We have a lot of them this year. They are great in breads and cookies. (Big Stone City, S.D.)

A: Try putting them in the freezer for about 72 hours. Freezing the walnuts should crack them open. If they are not cracked completely, take a screwdriver and twist along the crack that has developed. This will take some twisting and holding with a vise or something similar, but it can be done. I think I have seen black walnut "crackers" in a mail order catalog somewhere.


Q: I have read articles about people wanting to get rid of their black walnut trees because they consider them weeds. Iím trying to grow trees from nuts that I have acquired. What is the best way to get them started? I have about fifty nuts in black shells. Do I soak them in water with or without the shell? They have been in a box in my shed so they have been subject to below zero temperatures. How long should I soak them or is soaking them the wrong thing to do? (Parkston, S.D.)

A: The black walnut is indeed a very valuable tree. You have met the stratification requirements for germination but they may have dried out from low relative humidity. Your best bet is to collect the nuts in the fall right after they have fallen from the tree and then remove the outer husks. After cleaning, separate the unfilled nuts from the filled ones by floating them in water. The floaters are dumped. Place the seed either in the ground where you want them to grow or in containers for transplanting Keep them moist until freeze-up. You can expect an average of 50 percent germination.


Q: I have a problem and I need your help! How do you arrive at a monetary value for damage done to three black walnut trees that are 30 or more years old? The trees are on private property and all of the lower limbs were cut off by the city. These trees have never been pruned before. (East Grand Forks, Minn.)

A: Good luck! Contact the city forester or any competent forester or horticulturist knowledgeable in tree evaluation. There is a rational procedure that is followed and respected by most appraisers and insurance companies.


Q: We recently had two 40 foot black walnut trees removed that were about 15 feet apart. We would like to plant a blaze maple next to the site of one of the black walnut trees. Do you know if the blaze maple will grow on the site, or might it be impacted by the black walnut toxins? (E-mail reference)

A: Good question. There has never been any documented research showing the allelopathic effects of black walnut on anything other than members of the tomato family. You will have a greater allelopathy on the tree you plant if you allow any turfgrass sod to grow within 12 inches of the trunk of the tree you are intending to plant. I would say go ahead and plant the maple.


Q: Can you tell my why Colorado blue spruce trees only have cones on the topmost branches? Also, what does a person do about little white worms in the black walnut husks? (Canova, S.D.)

A: Your observation of spruce cones only forming on the topmost branches has got to be a local or isolated phenomenon. Most that I have seen will form the cones all over the tree. Balsam fir form their cones only on the top part of the tree—a genetic characterization.

Spray the black walnut with Sevin or malathion when the tree is in full flower. Do so when the bees are not active.


Q: Enclosed is a sample of our mountain ash and a few leaves from a tree that I cannot identify. The ash blooms and gets berries, then it dies off, and is now getting some dead leaves. We also have three apple trees right next to the ash that we were told have fireblight. What can we do to save these trees? We did try spraying Malathion at the time of blossoming, but it didn't help. (Berlin, N.D.)

A: My suggestion is to get rid of the badly diseased apples and mountain ash, and allow the black walnut that is growing among them (probably planted by a squirrel) to thrive.

The apple and mountain ash are members of the same family, and both are susceptible to fireblight, along with other diseases. Once they are hit as hard as yours are, there is little that can be done to save them. Enclosed is a publication of apple cultivars that are more resistant to diseases ("Tree Fruit Culture and Varieties in North Dakota"H327).


Q. Enclosed please find two apple exhibits. Exhibit A comes from the family farm north of Turtle Lake. It is a good producer and an excellent keeper. It is good for fresh use and for processing. Exhibit B comes from a lot in McClusky. I took some with the owner's permission and the apple has an excellent tangy flavor and is also excellent for processing. I would like for you to identify them for me. I have no idea what their botanical names might be.

I am also enclosing a catalogue clipping which offers a Japanese Persimmon hardy in zone 4. I live in a protected area here in Beulah close to zone 4. Please tell me what you   might know about the Japanese Persimmon. I am wondering whether any type of persimmon might be reliably hardy in the Beulah-Hazen area.

My last question involves walnuts. It seems that a few folks have luck with growing black walnuts despite the fact that they are listed as zone 4 hardy. Why don't more people grow  butternuts instead? The butternut is listed as being zone 3 hardy. It is a better quality nut, and it reaches maturity and produces sooner than the black walnut. Please tell me what you might know about this subject. In closing I wish you a Merry Christmas and a happy New Year. I also thank you for all the useful information which you have afforded me in the past. On a personal note, I truly wish that you could appear at some sort of lecture let's say in Bismarck so that I as well as other interested folks might hear your input. (Beulah, N.D.)

A. Identifying apples is done mostly by consensus. Many are like trying to identify the difference between twins.

Dr. Jack Carter, Larry Chaput and I came up with the following: Exhibit A - Minjon; Exhibit B - Sweet Sixteen. I have enclosed our current circular H-327, "Fruit Tree   Culture and Varieties in North Dakota," to help you consider others.

Much depends on the seed source for the hardiness of the black walnut species in our region. If you plant some, make sure they have come from a North Dakota source. Black walnut is favored, I suppose, for the potential value of it's lumber, in addition to the nuts. The butternut is a beautiful tree and is valued as a timber source. It could be that people take pride in growing something that is not supposed to make it in our region.  

I wouldn't put any dollars or effort into growing persimmon, in spite of what the catalog says. They need a great deal of moisture and well drained soil two things North Dakota is usually short on. Besides, their fruits don't ripen until late October and by then, as you know, we could be entering winter.


Q. I have a black walnut tree that drops bags full of walnuts. Over the years I have started a few from seed and am enjoying watching them grow. However, I am looking for the proper method of planting and starting these seeds to get better results. Is there a right way, a right time, a right method?

Thank you. (Hawley, Minn.)

A. There is always a "correct" way to do things, but if what you are doing is resulting in satisfaction, why complicate your life?

Well, in case you do, I have enclosed copies of the germination procedure and some pages of text--too much to boil down to a simple response. You will note after reading everything, that what you are doing is basically correct.

Enjoy!


Q. We have a black walnut tree that is several years old. This year for the first time it had nuts on it. Would you please tell me if they are edible? I have two peony plants that are five years old. They look very healthy. They get lots of buds every year, but they never bloom. The buds turn black and fall off. Could you please tell me what the problem might be?  (McClusky, N.D.)

A.Yes, the fruit of the black walnut is edible. The tough part is getting to it. You will likely need a three-pound sledge and a concrete block to crack the shells!

Peonies are sometimes subjected to a disease known as grey mold  (Botrytis spp.). In this case, good sanitation practices such as spring and fall cleanup and the application of Daconil 2787 (all-purpose fungicide) during bud formation will help.

There are also other causes for failure to bloom that are not related to diseases:

1. Planted too deep or too shallow
2. Immature transplants
3. Crowded plantings
4. In too much shade
5. Insufficient nutrients


Q: How do you start a black walnut tree? I have two black walnuts from a tree and they are starting to turn dark. (Greenbush, Minn.)

A: If you can crack the outer husk with a hammer, do so, and plant the nuts where you want a tree to come up. Set them down about 6 inches in the soil. If the seeds are viable, germination will take place next spring. If you havenít already discovered, wear gloves when handling walnut fruits as they do an excellent job of blackening oneís hands -- for a long time!


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