A favored garden plant since at least ancient Roman times, the oleander (Nerium oleander) is a garden workhorse at U.S. Department of Agriculture plant hardiness zones 8 through 10. Tolerant of heat, drought, most soil types, wind and coastal conditions, oleander has a long flowering period and does not have serious diseases or pests. Grown most often as an everyday tree, oleander suits more formal settings when prepared to develop as a standard, which can be a small, single-trunked tree having a head of leaf on top.
Choose a young oleander bush that’s one to two years old, either at a nursery container or in the ground. Select the strongest, straightest, most central stem. Prune off all the additional stems, cutting the branches as near the stem or the ground as possible. Use pruning shears equipped using a solution of 1 part household bleach to ten parts of water to wash the pruners.
Put a bamboo stake into the ground beside the straight stem and secure the stem to the stake in 2 regions with plant ties. Cut back any side branches on the primary stem from about half their length.
Water the plant once the top inch or so of soil becomes dry and enable the plant to develop. Transplant container plants into larger pots that have drainage holes as required so the oleander does not secure root-bound. Move the stake together with the plant.
Shaping the Trunk
Prune side branches back to the trunk on the main stem as they develop through the next growing season. Allow the leaves to remain on the plant.
Insert more ties to secure the trunk into the wager as the central stem grows. Replace the bamboo wager with a 5-foot-tall wooden tree stake once the oleander outgrows the bamboo stake.
Cut off the surface of the plant once it reaches the height you’d like the trunk to be, typically around 5 feet tall. Eliminate the top just above a node, which will be where leaves come from the stem.
Shaping the Head
Allow three to five divisions to grow from the top two nodes of this main stem to start the head.
Cut back the branches by about half, cutting just above a node.
Permit more divisions to develop from the original ones, and prune each of these back to about two nodes. Eliminate branches from the middle of the canopy and encourage peripheral branching to complete the contour. Shape the head to a rounded type as you prune.
Continue to remove any side branches that develop from the oleander’s trunk as you contour the head, and remove leaves that remain on the trunk.
Maintaining the Form
Cut off any side shoots that grow from the trunk as close to the trunk as possible for the life span of this plant. Prune away stems that grow from the base of the trunk.
Prune the head to maintain the desired size and shape, with major pruning done in the autumn to encourage new spring flowering growth. Perform lighter pruning during the growing season to avoid crossed branches or to thin out regions of crowded growth.
Keep the trunk staked after the head is formed for at least several years until the wood is strong enough to support the head.