Walnut trees are majestic and popular trees grown for their nutritious and tasty walnuts and for their beautiful timber. While walnut trees are easily grown from seed, they are not easily transplanted. The roots of most trees grow more outward than downward. The walnut tree, however, has a substantial tap root. This root grows straight down and deep into the ground as the walnut tree's trunk grows straight up and into the sky. This trait of the walnut tree makes it very difficult, but not impossible, to transplant.
Wait until fall after the leaves have dropped--but before the ground freezes--to remove your walnut tree from the ground. This will give your tree a chance to grow new water-absorbing roots before you transplant it.
Water your walnut tree two or three days before the transplant if the ground is dry. The roots of your tree should never be allowed to dry out.
Dig at least a 2-foot-deep trench (assume that the tap root is as deep as the tree is tall) in a complete circle around your walnut tree. Dig the trench with a radius of 6 inches for every 1 inch of trunk diameter. This trench will help you to achieve the angle you will need to undercut the root system.
Use a sharp spade that will cut straight through any root it encounters to minimize damage to the root system. Dig at an angle, severing the root system from the ground, creating a root ball. Do not attempt to remove the tree before the root system has been severed from the ground.
Leave the dirt around the roots as a root ball. Use a sharp blade to clean out any damaged, circling or kinked roots before covering the root ball with damp burlap or canvas to keep the roots from drying out, while your walnut tree is waiting to be replanted.
Plant your walnut tree in a hole two to three times the size of the root ball. Use your spade to roughen the sides of the hole.
Back-fill the hole, planting your tree at the same depth and in the same position to the sun as it was in its previous location. Gently but firmly tamp the soil in around the root system and water your tree thoroughly to help further settle the dirt, as well as to keep the roots moist. Apply mulch to maintain moisture.