Mimosa trees or silk trees (Albizia julibrissin) grow readily in hardiness zones 6b to 9, spreading their seeds widely. Gardeners who plant one tree may soon have several due to its aggressive propagation. Transplant mimosa trees if they don't have enough room to grow, if they're not planted in full sun or simply to site them in another part of your yard. In temperate areas, transplant the tree in either spring or fall. Gardeners in the northern end of the mimosa tree's range should transplant only in spring so the tree is acclimated to its new environment before winter.
Water the mimosa tree until the soil becomes saturated for two days prior to planting. This loosens the roots, making it easier to dig up the tree.
Select a new location for the mimosa tree that provides full sun and enough room for the tree to mature. When fully grown, mimosa trees average 15 to 25 feet in height and 25 to 35 feet in width.
Dig a hole at the new spot that's twice as large as the plant's root ball. If you're transplanting a container tree, you can estimate this easily. If you're transplanting a ground tree, use the Garden Line's estimate of 9 to 12 inches of root ball per inch of tree trunk diameter.
Remove rocks, weeds and roots from the hole. Jab your shovel at the bottom of the hole to roughen the dirt, which will help your mimosa tree adapt to its new environment.
Dig your mimosa tree out of the ground. Begin at a distance twice the size of the root ball and dig into the ground with your shovel. Work closer to the tree and down; as you edge close to the root ball you will see roots, which can guide your digging. Keep digging until you've unearthed the whole root ball. If you're moving a container tree, skip this step.
Tug up on the trunk of the mimosa tree to free it from the ground. It should come readily, but if a couple of roots cling to the ground, cut them with clippers.
Carry the tree to its new location, or place it in your wheelbarrow and wheel it. Set the tree in the new hole so it sits at the same depth as it was planted before. Ensure the tree is vertically straight.
Backfill the hole with soil to transplant the tree. Firm the soil around the tree's roots and trunk gently.
Water the mimosa tree to settle the soil and remove air bubbles. Add water until the soil grows saturated.