How to grow black walnut trees from seed

black walnut

Black walnut trees are highly sought after. Foragers collect their fruits from midsummer through early fall to enjoy the rich flavor of their nutmeats – if they can beat the local wildlife. They are also among the most desirable hardwoods for furniture and cabinet making. Even their hulls can be put to use to make unique wood stain.

Black walnut trees are still considered abundant throughout the Midwest; however, they are not as widely dispersed as they once were due to being harvested for lumber. Black walnut wood is desirable because of its deep color, its dimensional stability and resistance to splitting and the fact that it seldom decays in the center. It’s actually a stronger wood than white oak. A large walnut tree or a stand of trees can reap a decent pay day.

Walnut trees planted today wouldn’t become mature enough to timber for 40-60 years. So planting a grove intended for lumber would be an investment for retirement or future generations. Fortunately, you’ll be able to enjoy shade and foraging opportunities much sooner.  It only takes 10-13 years for walnuts grown from seed to bear fruit.

If you would like to plant walnut trees there are a few considerations you need to make to ensure success. Learn how to pick an ideal planting site, choose viable seeds and ensure seed germination to successfully grow a walnut tree from seed.

Choosing a location to plant walnut seeds

Walnut trees grow most abundantly along stream banks, along watercourses, in bottomlands, open fields and along the edges of forests. They prefer full sun and deep, moist, rich, well-drained soil. They will grow in soil containing clay or rock, but much slower than seeds planted in unobstructed soil. Additionally, they prefer soil with a pH of 6.0 to 6.5.

Once you find a location with ideal growing conditions, the next consideration you need to make is what else is growing nearby. Black walnut tree roots produce juglone, which can affect other plants growing in close proximity. These plants include pines, potatoes, tomatoes, blackberries, alfalfa and apples. You’ll have to find a location with ideal growing conditions where your walnut tree will not negatively impact neighboring plants.

Determining whether seeds are viable

Not all the walnut seeds you’ve collected will be viable to grow a tree. You can determine viability and how many seeds to plant per hole by following these steps:

  1. Remove husks.
  2. Place nuts in a bucket of water.
  3. Discard floating nuts.
  4. Save nuts that sank to the bottom.
  5. Crack open a small sample of the nuts you have left to determine viability. Viable nuts have white, solid meats; non-viable seeds have beige, shriveled kernels that are watery or give off a foul odor. The percentage of viable seeds in your sample will help you determine how many seeds you need to plant per hole to ensure success.
  6. Figure out how many seeds to plant per hole. If 80-100% were viable, plant 2 seeds per hole. If 60-80% were viable, plant 3 seeds per hole. If 40-60% were viable, plant 4 seeds per hole. If less than 40% were viable, plant 5+ seeds per hole.

Ensuring germination of black walnut seeds

Before walnut seeds will germinate, they have to be exposed to cold temperatures and moist conditions. This can be accomplished by planting nuts outside in the fall or by stratifying them indoors over winter.

Planting outdoors

Black walnut seeds should be planted about 2 inches deep in moist soil in the fall. If you’re planting more than one seed per hole, space them out so that unwanted seedlings will be easier to remove later.

Stratifying indoors

Stratify walnut seeds by placing them in a moist mixture of sand and peat moss and then storing them in a cool location. You can store them in the refrigerator in plastic containers or food storage bags. The stratification process takes 90 to 120 days. Check periodically to make sure your seeds have not dried out.

After they’ve been stratified, they can be removed from the refrigerator and planted in the spring.

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    • Carol,

      You can remove the husks when they are green or black, but it’s much easier to remove them when they are black and dried out. I would also recommend using gloves to remove the husks because the juglone in walnut husks will bind to your skin and turn your hands black. It takes a long time for it to finally fade and be washed away.

  1. If starting the seeds in a container, what size container should be used? Also, is it advisable to permit the container grown trees to get to say 2 ft high before transplanting into the ground? Should this be done in spring or fall?

    • You can start walnuts in containers that are about 20 inches wide and 18 inches deep. You should transplant the small walnut trees when they are about 1 foot high. Early spring is the best time to transplant.

    • Penny,

      You could try mechanical barriers to keep them out. I found this information from the USDA Forest Service Northern Research Station — Or, you might also try putting peppermint oil on/around the seeds because most animals that dig them up find them by smell and are deterred by peppermint oil. I hope that helps and good luck!

    • There’s a possibility some of them could still sprout, but, depending on your location, they should have emerged by now. I’m not sure how deep they were planted, but another thing that could be affecting them is leaving the husks on. Ideally, they would be removed and you would test the viability of the nuts using a bucket of water before planting them.

    • It’s only really necessary to use it until your trees become established. I would say through the first growing season would probably be enough.


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