How To Grow Black Walnut Trees From Seed

Growing Black Walnut Trees from seed is an easy activity that one can do in the fall to obtain new trees for little to no cost. You simply need to test the nuts viability be performing the float test, then cold stratify or winter sow the seeds to overcome dormancy. Finally, we can plant the nuts 1-2″ deep and expect them to germinate in the Spring.

Baby black walnut trees

I’ve grown and propagated hundreds of trees in my life. And for Black Walnut, this is the best method I’ve found. I’m going to show you exactly what I do from harvest to germination.

Black Walnut trees can be propagated from the nuts that the tree produces. After the walnuts naturally start falling from the tree, you should collect some from the tree itself, not the ground. Then, remove the husk and test the black walnuts viability by seeing if it sinks in water. Plant viable Black Walnuts 1-2″ deep. Trees will sprout in the Spring.[1][2][3]

If you collect some black walnuts and wish to grow them from seed, you first need to do a test to make sure the nut is a viable seed. Also, Black Walnuts need to undergo cold moist stratification or be winter-sown to germinate.[1][2][3]

Harvesting Black Walnuts for planting

In late Summer, Black Walnuts will begin to naturally fall from the tree. Sure, you could go grab them off the tree earlier, as they are quite visible by mid-Summer – but the seed (embryo) inside that nut hasn’t fully developed yet! You want to leave the nuts on the tree as long as possible, and only begin harvesting once the nuts naturally fall from the tree. Doing this ensures that the embryo had all the time it needed to fully develop[4].

Black Walnut on tree

So, although you may be tempted to harvest the nuts early – don’t! Just have patience.

Also, you should plan on gathering twice as many walnuts as you want trees. The germination rate can be anywhere from 40-90%, so it’s better to have more to plant.

Removing the husk

Next we need to remove the husk. There are many methods for doing this – some easy, some challenging. If you are just trying to grow a handful of trees though, a simple chef’s knife or hunting knife will suffice. Also – wearing some protective gloves will keep your hands clean. This is optional, but you should know that the husk will turn your hands yellow to brown!

If you leave the walnut to sit in it’s husk for a while (away from squirrels), the husk will soften and begin to turn black. This makes it easier to remove. But, follow the steps below to remove the husk.

  1. Place your freshly harvested walnuts on a cutting board or piece of scrap wood.
  2. Using a large knife, slice into the husk until you hit the hard wall of the nut shell.
  3. Carefully (keeping your other hand out of the way of the knife) roll the nut forward, applying gentle pressure against the shell of the nut.
  4. Twist the knife (pushing blade away from your other hand) or pull apart the husk, revealing the nut
  5. Rinse and soak the nut in water several times to remove most of the dye (optional)
  6. Float test the nut for viability.
infographic for how to remove black walnut husk

If you leave the walnuts in your garage

Testing Black Walnut seed viability

Now, just because the husk has been removed and the nut has fallen from the tree doesn’t mean the embryo inside the shell is viable to germinate. Unfortunately insects can burrow into the the husk and nut, eating the embryo via tiny holes. Also, sometimes a tree may ‘abort’ a nut (often in times of stress or drought), or the embryo can not fully form.

When any of these above scenarios happen, it usually results in air pockets inside the shell. And it is because of these air pockets that we can test the viability of the nut by trying to float it in water[5]. This test really works, and there is scientific research to back it up. If you are curious for a more detailed explanation, see my write up of the ‘float test’.

float testing black walnuts
Testing black walnut seed viability

But to test the viability of the Black Walnuts, simply float them in water for at least sixty seconds. Nuts that sink are viable, while those that float may not be. If you want to be completely sure, you can leave the walnuts in the water for 12-24 hours and then discard any floating or suspended nuts.

Storing walnuts before planting

If you wish to wait on planting your walnuts until Winter, then you should take care to store them properly. After the float test, dry off the nuts and place them in a sealed plastic container in the refrigerator. Nuts that are allowed to sit out in the open air will dry out. And thus the embryo inside will die, and the nut will no longer be viable.

Direct sowing Black Walnuts

At this point, you know you have viable nuts (haha), you can plant them in a suitable location (see here for growing conditions). But just plant the nut about 2″ deep in the soil. Now, you aren’t quite finished yet, as you will need to protect it from squirrels and rodents digging up the nut.

To keep squirrels from digging up walnuts you planted, place a piece of 12″x12″ chicken wire over the place you planted the nut. To keep it in place, place a rock or heavy weight on top. This will frustrate and prevent any rodent or squirrel from treating themselves to your soon-to-be tree.

If you wish to start your walnuts in pots though, continue to the next section.

Cold Stratify walnuts for germination

Black Walnuts have a dormancy mechanism preventing premature germination. To overcome this, we must either cold stratify or winter sow the seed.

Cold stratifying Black Walnuts in the refrigerator

To cold stratify and store Black Walnuts prior to planting, get a large 1-gallon zip-lock bag and some sand or vermiculite. Mix the sand/vermiculite with water so that it is damp. The amount of dampness is that if you squeeze a handful only a couple of drops should drip from your hand.

Then, place your Black Walnuts into the center of the mixture, and place into the zip-lock bag. Store this in the fridge until you are ready to plant.

How to plant and germinate Black Walnuts

This section is applicable if you plant to Winter Sow (my preferred method) the walnuts or for planting after you have cold stratified in the fridge. But I will describe it in terms of winter sowing.

Since Black Walnuts need a cold treatment, winter-sowing is the easiest method. Just let mother nature do the work for you.

  1. Fill a container with moist potting soil. The container should be at least 6″ deep (9-14″ tree pots are better).
  2. Planting Depth – Plant Black Walnuts 1-2″ deep into the soil (2.5-5 cm)
  3. Set the container outside in a location that receives morning sun and afternoon shade. Alternatively, you can place the container in an unheated garden shed or garage. This will raise the germination rate in zones 3-6. Black Walnuts are resistant to freezing, as they the shell that acts as insulation, however, they just need to be in cold weather (~40F). They don’t need the freeze/thaw cycles.
  4. Protect the container from squirrels and rodents. Hardware cloth, screens, or something similar with a rock on top works great.
  5. Germination will occur in roughly the middle of Spring, once temperatures begin warming up overnight
Black Walnut seedling right after germination
I had 60% germination rate of Black Walnut Trees the first year I grew them

Video guide to growing Black Walnut Trees from seed:

Below is a short video on how to grow a Black Walnut tree from Seed. This video contains all information you need to successfully germinate the nuts.

As an aside, while I was transplanting some Black Walnut seedlings into larger pots, I was able to get an up-close view of the embryo within the nut. Have a look at this picture – it really shows the anatomy of a Black Walnut that has germinated!

A Black Walnut seedling and the embryo contained within the hard black shell. I just thought this was a really cool picture.

Planting and protecting young trees

Once you’ve got germination, you can begin to think of where you will finally plant the young saplings. Walnuts grow best in full sun and moist to medium moist soil that drains well. If you are planting to produce nuts, you should space the trees 12-20′ apart.

Young trees should be protected from both squirrels and deer. Squirrels will dig up new trees to get at the nut even after germination. And deer will rub their antlers on young trees in fall during the rut. I strongly recommend you use plastic tree shelters with stakes, or cages to protect them. I do this in my yard with all trees that I plant.

Propagation from cuttings

While it is possible to take cuttings from a Black Walnut tree, it probably won’t survive. Black Walnut trees have an extremely low success rate for propagating via cuttings. Hess found that only 2-5% of softwood cuttings would survive.[6]

Final thoughts

The process for germinating Black Walnuts is fairly straight forward. The key is to wait until the nuts have finished growing before you harvest, test their viability by floating them in water (and keeping the sinkers), and then cold stratifying/winter sowing and planting. And – do not forget to protect your nuts or young trees from squirrels!

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[1] – Dickerson, John, BLACK WALNUT Juglans nigra L., USDA NRCS Plant Fact Sheet, 2001. Accessed 18JUL2021

[2]- Russell M. Burns, Silvics of North America: Hardwoods, U.S. Department of Agriculture, Forest Service, 1990, pp391-399. . Retrieved 18JUL2021

[3] – Funk, David Truman, Genetics of black walnut, U.S. Dept. of Agriculture, 1970, pp13.

[4] – ‘Growing Black Walnuts For Home Use’. United States. Agricultural Research Service. Crops Research Division; United States. Entomology Research Division, 1963. pp.8

[5] – Williams, Robert D. “Black walnut seed: from tree to seedling.” Annual Report of the Northern Nut Growers Association 72 (1982): 141-146.

[6]- Hess, Charles E. The vegetative propagation of black walnut (Juglans nigra L). A report of research conducted under Cooperative Agreement Supplement No.16 to the Master Memorandum of Understanding of June 1, 1953, between the Forest Service and the Purdue Agricultural Experiment Station, Contract No. A9fs-12234, 11p.

Joe Foster

Hi - I grew up outdoors in nature - hiking, fishing, hunting. In high school I got my first job at a garden center where I learned to garden and landscape. I've been growing plants from seed and designing native plant gardens for over 10 years. I hope to share some of my knowledge with you! You may have seen some of my videos I create on our YouTube channel, GrowitBuildit (more than 10 million views!). You can find my channel here: Additionally I am a wood worker / DIY enthusiast. I enjoy designing/building projects (with hand tools when I can!). I hope to give you some tips and useful information!

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