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Past Articles Library | Trees | How to Grow Black Walnut Tree


Black walnut trees are a beautiful hardwood tree that can fit into some landscapes.  Reasons for a statement like this are vast but include the height of the tree, the terrain requirement, and the amount of time it takes for the tree to mature.  All of these reasons can be a negative to planting a black walnut tree.  But if you have the right environment, this hardwood tree will provide you with years of beauty and enjoyment.

The black walnut (Juglans nigra) requires a landscape that is gently sloping.  This will allow the tree to grow big and tall.   If you are forced to plant on a slope make sure that the planting location is north facing or consider planting near a creek and/or in a floodplain area.   Never plant on top of a ridge, south-facing slope or steep hillsides. 

Once you have your location selected, the next step is to check out the soil.  It needs to have a pH of 6.0 to 6.5 and be well draining.  To test the soil’s root percolation one will need to dig a hole that is at least 48 inches deep.  As you dig, notice the soil.  If there is clay or it is mottled in color (difference shades of brown), then you will need to choose a new location.  If on the other hand, you hit gravel within the 40 inch range you will be faced with a tree that grows twice as slow as a tree planted in a location where the roots can reach 48 inches or deeper without obstruction. 

Now that you have a location proper location picked out, the next step is to choose your planting method.  Black walnut trees can be planted as seedlings or you can start our own from black walnut seeds (nuts).  If you choose to plant seedlings, make sure to choose a local supplier.  This means your seedling should come from a radius of 100 miles from where you live.  The reason for this is the fact that your tree will already be adjusted to your local environment, which includes temperature and moisture levels.

Black walnut seedlings can be ordered for fall or spring planting but if possible get your seedlings in the ground during the fall.  Prior to planting, the ground will need to be prepared.  Black walnut trees do not like competition.  In doing so, the ground will need to be weed-free.  To do this, till the area up as if you were preparing it for a garden.  

Once the garden has been prepared, the next step is to outline the required spacing.  Black walnuts need a lot of space.  Giving them their room will allow the tree to grow tall and straight, which is a requirement for timber sale.  The spacing needed for a mature tree is 100 to 150 feet per tree.  To achieve this one can mark out a 10 by 10 or 12 by 12 grid system for each tree.   This can be done with lawn paint or powdered milk.

After the grid has been marked, the next step is to plant the tree.  This is done by digging a hole that is no deeper than the container or rootstock of the tree but two to three times the width.   Prior to planting the tree make sure the hole is not too deep.  To do this, place the seedling in the hole and run your hand from the seedling to the ground.  If the levels match, then the seedling is ready to plant.


If, on the other hand, the soil level is too high, then dig the hole deeper but if it is too low, fill in.  Once the soil level is correct, place the seedling in the hole, backfill with removed soil, and then create a berm around the hole to hold water.  Repeat the process with each seedling but do not fall into the trap of thinking that any hole will work for any seedling.  It is very important to make each hole personal for each tree.

After the tree(s) have been planted, the next issue you will be faced is weeds.   As stated before, black walnut trees do not like competition and their canopy is not thick enough to block out the sunlight, which would deter weeds.  At this point you have three choices.  One choice is to control the weeds through a chemical application, which I do not recommend.  Second, you can plant your seedling in a landscape cloth/ plastic mulch and carefully mow.  But this choice can be very time consuming.  The best approach is to intercrop between the black walnut trees with another type of hardwood on a grid size of 35 by 35 or 40 by 40.  Once the other trees have been planted, broadcast grasses such as orchard grass, fescue and/or clover.  After the seedlings are a few years old, grazers such as cattle or goats can be released to deal with the grasses.

If you want to start your own black walnut trees from nuts (seeds), the process begins with the nut selection.  You do not want any nut but that comes from healthy straight stock.  Also, you do not want old nuts for your seed stock.  The old nuts have dried and will not germinate.

Once you have your fresh nuts selected, the next step is the planting process.  Black walnut nuts can be planted directly outside in the fall but if you insist on planting in the spring, you will need to create a cold period prior to planting.  This can be done by placing them in the fridge or in an unheated garage but when using this approach, make sure to not allow the seed to dry out.

For each tree you want, you will need three nuts.  Black walnut trees have a low germination rate, which averages between 30 to 50 percent.  Once you have your seeds selected, prepare the ground as described above.  After that has been done, plant each nut three to four inches deep.  To keep squirrels from finding your nuts, cover with hardware cloth and then mulch. 

Pruning will need to be done every May through July.  This will keep the tree growing straight and should start when the tree is a seedling.  The first thing one will need to check is the top of the tree.  You do not want any forking.  To prevent this, one will need to examine the terminal shoot (top).  If the shoot is growing at an angle, it will need to be cut off.  If the terminal shoot is forking, tie the two pieces together and then cut off the weaker branch where it does not come together with the other branch. 

After the tree is three years old, you can begin to remove side branches.  Doing this simple task will make your tree(s) more valuable since there will be no knots in the wood.

While black walnut trees are beautiful, they do have one peculiar trait and that is they produce a growth inhibiting/killing chemical called juglone.   This means that pine and apple trees along with potatoes, tomatoes, and blackberries should never be planted near black walnut trees.



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