Start pulling your backfill soil mixture into the hole around the rootball tamping lightly as you go to remove air pockets. When you have filled the hole to the halfway point you can soak the soil. Then continue back-filling to the top edge of the root ball. Avoid placing soil on top of the root ball as doing so can suffocate your tree.
Step 6 (Optional)
If you are planting your Eucalyptus tree in a location that is far from a water source and in well-drained soil, you can use remaining soil mixture to build a 3-inch high water retaining berm (catch basin / doughnut) around the outside perimeter of the planting hole. This basin will help to collect water from rainfall and irrigation often reducing the need hand-watering. The berm can be removed after a year or so or when your Eucalyptus tree has established itself.
Next, deeply water the planting area, including the root ball, to a depth equal to the height of the root ball.
Apply a 1-2" layer of aged, shredded wood mulch or bark, or a 3-4" layer of pine straw, around your newly planted Eucalyptus tree. Avoid the use of freshly chipped or shredded wood for mulch until it has cured in a pile for at least 6 months, a year is better. Avoid placing or piling mulch directly against the base of the tree as this could cause problems with the bark.
How To Plant A Eucalyptus Tree In A Container
Eucalyptus trees growing in pots appreciate a consistently moist but well-drained soil during the warmer seasons. Therefore, choose a container with a drainage hole(s) at the bottom and use a quality bagged potting soil.
Container Size Matters!
Eucalyptus trees grow very rapidly. When planted in a container they can become root bound rather quickly. Therefore, it's best to choose a much larger pot to increase the time your tree can spend in the container. For example, if your Eucalyptus was growing in a 3 gallon nursery pot (10" rim diameter) you might want to transplant it to a container at least 18 inches or more in rim diameter. If in a 1-gallon size pot (6-6.5" diameter) transplant into a pot 14 inches in diameter, or larger.
Shape Can Be Important
Next thing to consider would be the shape of your container. Does the shape of the container allow the Eucalyptus tree to be easily removed from the pot without damaging the root system or the pot? Avoid vase-like pots with narrow tops. The top of the pot should be as wide or wider than the bottom of the pot.
Wind Is A Concern
Is the bottom of the pot wide enough to support the Eucalyptus tree in wind? You don't want a pot with a very narrow base as it will be prone to tipping in the wind, especially with tall-growing Eucalyptus species. You can place gravel, rocks or other stone materials in the bottom of any container to increase stability. However, keep in mind that this will make the container heavier for transporting. If you do add stone or other materials to the bottom of the container, lay landscape fabric over it.
Do I need a lightweight container that can be easily moved? Clay, ceramic, and concrete pottery are typically much heavier than plastic or synthetic materials, and they are prone to breakage. That said, if there will be exposure to wind, heavy concrete might be the best way to go. Double walled plastic or synthetic containers provide better insulation from freezing and hot conditions. Galvanized tubs or wooden planters work nicely and can be painted or stained. Bricks or stones can be added to lighter pots to increase stability. Just make sure whatever pot you use has a drainage hole(s) at the bottom.
Container Planting Instructions
Before filling your container with the soil mix, I suggest lining the bottom with shade cloth or a porous landscape fabric. This will keep the drain holes from becoming stopped up with soil. If you place gravel or other materials in the bottom of the container lay the fabric over it.
To remove your Eucalyptus tree from the container it was growing in first tap on and or squeeze the the sides of the container to loosen the root ball. Then firmly grasp the base of the trunk and very gently try to lift and remove the tree from its container. If the root ball is stuck cut the container away.
CAUTION: After having removed the plant from the container it is not necessary to loosen or spread out roots, which could damage the sensitive root system.
Pour a small amount of your soil mixture in the bottom of the container. Set your Eucalyptus tree in the container and make necessary adjustments by adding or removing some soil so that the top edge of the root ball will sit 1/2 to 1" below the rim of the container.