Basically for the home garden the way to go is to train the tree into a single trunk. Unfortunately, this may not be the way your macadamias, especially tetraphyllas, want to grow. Yes, you should choose only one trunk. Choose the best and strongest, most upright of the three trunks coming out of the ground. (Look closely to make sure it’s the grafted one!) Cut the others off at ground level. This may sound drastic but it’s the best way.

If the chosen trunk leans, drive a stout stake into the ground about 3 or 4 feet from the trunk on the opposite side from the way the trunk leans. (Siting the stake too close to the tree can damage roots.) Put a non-abrasive strap around the trunk to straighten it up, and adjust the tension from time to time. Don’t stake it with other stakes, just one. (Remove any other stakes that it may have come with it from the nursery. You want the trunk to move in the wind so it will get strong. If more sprouts come up from the ground cut them off too. You may have to keep at this for a few years.

When trees are young, leaves come out of the trunk all the way up. Every time there is a leaf there will be three or 4 buds above it. Until the tree is 4 or 5 feet tall, keep rubbing out or clipping off all but the biggest and strongest, most upward pointing of these buds. Do not let the others grow because you want one single trunk that will be whiplike while it is growing to the height you want. You just want this one upward-going whip to reach 4 or 5 feet. When the tree is 4 or 5 feet tall then you can then let it branch, but it’s best not to let all the buds grow into branches in one spot on the trunk or a strong wind could split your tree into two or even three parts and all would be lost. The best way is to continue having a central leader. Then let branches form on the sides but not opposite each other. Ladder these lateral branches up the side of the trunk and surrounding the trunk allowing one branch to stay on the tree every 6 inches on the way up but on different sides of the tree.

As the branches grow pinch back their tips from time to time so they will put out side twigs that will be the nut-bearing twigs. Always try to encourage branches to grow parallel to the ground and not at a steep V angle to the trunk. V-shaped joints are weak and can break if loaded with nuts or hit by wind. Macadamias have hard wood but it is brittle. They are not very fast growing. You can sometimes spread a narrow V joint to a wider angle by taping a piece of bamboo at an angle from the trunk to the branch while the branch is still very young so the wood is softer. This can force the branch down and make it grow more level with the ground, but you will need to use soft cloth or a carefully carved shape to avoid bruising the bark. Another way is to hang a heavy lead weight on the branch, or use a rope to connect the branch with a big boulder under the tree. You see this sort of thing done in Japan, seldom if ever in the USA. It takes many years. The Japanese will leave these devices on for as long as necessary, even as much as ten or twenty years until the wood is hard and set into the shape they want. One Japanese gentleman told me that in some cases the supports are left in place for the entire life of the tree, but they are replaced with new ones as necessary.  Japanese horticulturists may use several pieces of bamboo in various spots down the branch. The trees are not unpleasant to look at. The supports are so artistically made that they become part of the ornamental look of the tree.

If a water sprout occurs on top of a branch (a whiplike growth growing straight up), cut it off about 6 to 8 inches in height and it will make more fruiting twigs. If a branch grows through the crotch of another branch, cut it off entirely or if space allows cut it to six or eight inches in length and it will make side twigs also. Make this choice taking into consideration that you want to shade the bark so it doesn’t sunburn but also you don’t want so much bushiness in the center of the tree that rodents can set up housekeeping in there.

When the tree is up to ten or fifteen feet and the shape is good you can let it grow with a minimum of pruning. From then on just remove dead or dying wood or crossing branches as described above. When the tree starts to bear, flowers will cascade down from the branches and if you are lucky they may be delightfully fragrant.

The fragrance of macadamia flowers tends to drift on the wind, most pleasant to experience. Good luck with this job. Gophers can be a problem also. I hope you planted your trees in a wire basket to protect them when young. If not, stay alert and keep a Black Hole Trap on hand just in case.