Pruning Macadamias

Gardening Question from Dave:

Hi Pat, the Beaumont macadamias are doing well – sending out new growth. I noticed that they each have 3 trunks coming up out of the ground. The Cates have one well defined trunk. Is this typical or should I get ready to do some pruning on the Beaumonts?  Ideally, I’d like the Beaumonts to be single trunk trees about 10 to 15 feet tall with a 10 to 15 foot diameter canopy. I’ve never seen an adult Beaumont so, I’m not sure what I should expect.Thanks in advance.

Macadamias photo

Answer from Pat:

You are so right about the paucity of information on pruning macadamias in the home garden. As a result, many home-grown macadamias grow unevenly and look more like a raggedy shrub than a tree. Some don’t bloom at all and thus bear no nuts probably because a sucker from below the graft was allowed to take over. The best home-grown macadamia I ever saw had a single trunk that was at least a foot thick and a rounded head of growth on top. It bore a bounteous crop of nuts every year. It was growing next to an irrigated horse pasture. It’s roots got the water from the pasture and the only fertilizer it ever got was horse manure.

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.

Photo by Starr Environmental

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Comments

  1. Hi Pat
    Just bought a property near Grafton
    It has a well established macadamia
    About 20 feet high,loads of fruit
    The tree is looking a bit pale and i would like to take the top out and give it afeed.
    Iran a citrus orchard for 5 years,could this tree be suffering from a magnesium defincy,also what would be a good pnk racio Bruce Bailey

    • Fertilization and water requirements of macadamia’s are far different from citrus. Citrus should be watered deeply and infrequently, macadamias can accept any amount of water as long as drainage is good. Citrus are heavy feeders, but macadamia trees are members of the protea family from Australian and as such they are light feeders. As my book states on page 122, the exact fertilizer requirements of macadamia trees are not known and overfeeding can actually harm them. The safest way to fertilize macadamia trees to mix 5 Tablespoons of fish emulsion into 5 gallons of of water and sprinkle the solution under the tree twice monthly during months when the minimum temperature is over fifty degrees Fahrenheit. If you wish to lower the tree by pruning, do so gradually over a period of at least three years or even longer, always cutting back to a side branch and making sure to leave adequate leafy foliage to shade the trunk and fruit. Cutting back hard will result in leafy re-growth at the expense of fruit. If the tree is looking pale and loosing some leaves and twigs but has “loads of fruit” it may be that the tree is in decline and fears it might die due to neglect or drought. Lack of water, mechanical damage, or general neglect might have caused some surface roots to die. (Macadamias often need more irrigation during hot weather, which might not have been done.) If this is the case, you can save the tree and encourage roots to regrow by pruning lightly all over to encourage vigorous growth, then watering well and fertilizing as I have suggested above. Additionally,—and this is important—apply the fish emulsion solution as a foliar fertilizer by spraying all over the foliage in the evening or early morning twice a month for several months. Also, apply fresh mulch over the roots. It may take a few months or even a year, if the tree is in really bad condition, for your macadamia tree to grow new roots and to bounce back to health. Read the label on the fish emulsion to make sure it does not contain added phosphorus, and always be careful to avoid fertilizers that contain high amounts of phosphorus, since Australian plants do not like phosphorus. (As I stated above, macadamias are Australian plants and since there is little phosphorus in Australian soil, Aussie plants do not need phosphorus. In fact, heavy applications can kill them. If the former owner did not know this they might have been over-feeding or feeding with a “balanced” fertilizer, such as 14-14-14 containing too much phosphorus for the happiness of a macadamia tree or any other Australian plant.) Another possibility might be lack of trace minerals, as you have suggested. If older leaves are yellow with dark green veins, this is chlorosis due to lack of iron, zinc or other trace minerals, which I am sure you already know from your experience with citrus. Treat with chelated minerals or, to be safe, do a soil test first to determine the problem. Even without a soil test, an application of John and Bob’s Soil Optimizer might cure the lackluster problem and should help stimulate root growth. Another suggestion is to treat the ground under the tree with kelp meal or liquid seaweed emulsion. Either one of these is a safe, organic method of providing trace minerals.

  2. hi there Pat. We have a tree its about 40 yrs old in my mums garden. No one did much to it other than limiting growth by trimming it in a way that it has stimulated growth and its now somewhat out of control. Its mostly healthy but has some deadwood in the lower western part of it. It give lots of nuts but they are hard to collect as its on a slope with other things around it and it overgrows the fence. Its care has passed on to me and i want to trim it in such a way that we can collect the nuts with all of the bits of shade cloth we have around the place (rather than feed the rats), but am a bit unsure of the pruning method. it has several main branches and its probably 30 ft tall. My plan is to seriously trim back some of those branches to make a compact shape and also take out the crown. If it can be said to actually have only one. Feasible?

    • If you prune your macadamia tree as you have suggested it is unlikely that you will kill it because macadamia trees are very resilient to pruning. I hope, however, that when you accomplish “taking out the crown”, which sounds very drastic, you mean drop-crotching the tree down to side joints so it can keep on growing. In other words as with any tree, don’t lop off branches in the center, leaving stubs. Always cut down to a joint in order to leave tips that can continue to grow. I hope, also, that you realize that you risk a dramatic loss of harvest and maybe you will get no harvest whatsoever for several years. The tree will quite likely bounce back with a lot of growth at the expense of harvest. Regarding harvest, it really is best to pick up the nuts every day while they are dropping or as you have correctly stated, rats will destroy much or all of your crop. Because rats also damage nuts on the tree most growers employ an active system of rat control, usually poisons, but in a home garden, these can be dangerous for families and dogs. Electric traps can work also. One home-made type of trap that is unfortunately a cruel way to kill rats is to half-fill a trash can with water and provide a ladder for a rat to reach one end of a flat and weighted hinged stick that has a glob of peanut butter mixed with sugar smeared onto the end that extends over the water. Rats find peanut butter mixed with sugar even more irresistible than macadamia nuts. Once the rat gets over the water, his weight which is greater than the weight at the other end of the stick, pushes down the stick. The result is one drowned rat and most likely after a while, several of them. It’s probably kinder to simply load ordinary rat traps witha little smear of this mixture. Stake the traps down so rats don’t run away with them and cover the traps with cardboard boxes with a hole in the side for a rat to enter. Birds are not attracted to the traps when hidden inside cardboard boxes.

  3. I planted a tree about 4 years ago and never pruned it. it looks like a 8 foot bush 8 feet wide. branches start about 3 feet from ground level.I had about 20 nuts last year and it has about ten nuts this year. several months ago, the new growth dried up and got brittle at the tips. only one tip of hundreds survived. I just read that I may have used phosphorous, but don’t know what I actually used. plenty of apparent healthy new growth is starting now, but there are gaps where the other growth died. my main question is how to prune a tree at this stage. I reside in central, eastern florida (fort pierce). my office purchased the tree for me in honor of my father who died. would it be good to use seaweed in mulch or blend seaweed with water and apply? any other ideas?

    • It sounds to me as if your tree was damaged by over-fertilizing. Burned and dead areas such as you describe sound like salt damage or burn from over-fertilizing. (Gopher damage can also cause die-back like a patch of dead branches on a tree. But I think there are no gophers where you live.) Since you don’t know what you fed the tree in the past or how much, it would be good to do a soil test. If there are too many salts in the ground, applying liquid gypsum, or spread bagged gypsum and then water in order to wash the salts to deeper levels. Also make sure that your tree receives adequate irrigation so that the soil retains an even amount of moisture at all times. The precise fertilizer requirements of macadamia trees is not known and over-fertilizing can actually harm macadamias. Macadamia trees grown in moist, fertile garden soil, well-mulched with aged compost or manure, will produce crops with no fertilizer whatsoever. The safest way to fertilize a macadamia tree is to apply a solution of fish emulsion, twice monthly over all the root zone during any month when the temperature is over 50 degrees Fahrenheit. Mix 5T. into 5 gallons of water and sprinkle all over the ground under your tree. If I were you I would undertake this system right away. To prune: Cut out all dead growth back to joints and leaving no stubs. Then during the next three years progressively prune—in other words gradually, not all at once— in order to form a tree with a single main trunk and a framework of horizontal branches, beginning about 3 feet from the ground and about one and one half foot apart from one another. Refer to a pruning manual since which variety you have may affect pruning requirements.

  4. Hi Pat,

    I just planted a grafted Beaumont Macadamia tree, about 5 feet tall. I took the stake out and it bends quite a bit. I supported it on three sides with stakes 3-4 feet away from the trunk. Is this right? How long should it be supported before it can stand up on its own in the wind? Thanks so much for your help!

    Cheryll

    • The way you supported your newly planted macadamia tree sounds perfect. Usually a tree that is trained this way will have a straight, strong trunk and stand up on its own within one year’s time. Occasionally, if there is a very strong wind from one direction, it may take longer. Keep an eye on the part of the eye or rope that goes around the trunk and lower branches, to make sure it doesn’t girdle the tree and limit growth. The old methods of running wires through an old piece of hose or using rubber straps to go around the trunk and lower branches still work but I see many left of these systems left on trees too long and squeezing the trunks of young trees preventing them from growing properly. There is a new product called Arbor Tie that is the best yet since its made of netting and expands with the tree

  5. Pat

    I have a tree I believe is 10-15yrs old. Apparently has never been pruned. It was in bad shape when we bought the house 1.5y ago, but has since turned around with some fertilizer tlc. It drops about 10 or so nuts a day, not sure if that helps to figure out how old the tree is. Anyways, I wanted to prune the tree, as it has some mature branches near ground level and up the trunk its a mess. What would be a good pruning plan for it? I have read no main branches below 36″ and a spiral up, but not sure if that is for mature trees that are dropping fruit. Thanks

    • It would be impossible for me to tell you how to prune this tree. I suggest you read what I have written already on pruning macadamias and try to follow as best you can. Prune off no more than ten or twenty percent of the unwanted growth each year and do not attempt to correct the tree all at once.

  6. Aloha Pat,
    I enjoyed reading your tips and pruning and feeding macnut trees. I just bought some land in Pahoa, Big Island Hawaii. There are 25 mature trees that have not had any care in 10 or more years. Elevation is 1200ft, and we get a lot of rain. Most of the trunk and many beaches are covered in moss. I was thinking about lightly pressure washing the moss off? Would appreciate your insights. Mahalo.

    • I strongly recommend you ask advice from macadamia-tree experts of the University of Hawaii before removing moss from trunks and branches of your macadamia trees. Cultivation, varieties and practices of macadamia growing differ by location. I live in Southern California, which has a dry Mediterranean climate. Thus many conditions, such as the growth of moss on trunks of trees, that you face in Hawaii usually do not occur here.

      I do not know the facts or best practices in this regard so you need better advice than I can offer, but just off the cuff it seems to me that removing the moss with a pressure washer or by any other means might cause unforeseen problems, such as disturbing the delicate feeder roots and protective mulch under the canopies of the trees and/or possibly applying more water to the ground under the tree than is desirable.

      Moss growing on trees might look unkempt, but usually does not harm the bark of the tree or the tree itself. It could be that removing the moss by any method might harm the bark more than leaving it alone. If you decide to do some pruning to allow more light and air circulation to penetrate your grove, this will help to slow growth of moss. However, with the heavy rainfall and elevation you describe, it is likely to re-grow even if you were to remove it.

  7. Thanks Pat! I will check with the University here and local growers first. Appreciate the reply!

  8. Have had a macadamia nut tree from a seeding for 6 YEARS and haven’t had any fruit yet. I want to know if i should prune it. It is approximately 10 foot tall and it has mulch around the trunk approximately 3 foot diameter. Would like some help please.

    • For pruning advice, please refer to “Pruning Macadamias” on this site. Regarding fruit: even grafted macadamias may take 6 or 7 years to bloom and bear, so wait another year. Unfortunately a macadamia grown from a random nut might never bear fruit or else it may take many, many years for it to do so. However, if your tree bears flowers and there’s no pollinator, you won’t get any nuts anyway. So, the first question to ask yourself is does your tree bloom? If yes, it needs a pollinator. Either your neighborhood has no other macadamia of the correct variety to pollinate your tree or there are no bees to accomplish the task.

      When trying to get a seedling to bear fruit, the best practice is to cut the top off and graft a named variety onto the roots. That way you will know what you’ve got and can also plant the right pollinator for it. My recommendation is that if it does not bear a crop next year I would either keep it or if you have no room for it, cut it down and purchase a grafted tree of a named variety. Be sure to provide it with the correct pollinator. However, if the tree does not bloom you could try damaging the bark in October by beating the trunk hard with a baseball bat or a garden hose. This practice often makes a tree bloom and bear. It’s worth a try!

  9. Hi pat!

    Can you please provide full information on how macadamia trees with many trunks can be pruned? at which period from planting date?

    • There is a difference of opinion on methods of pruning macadamias with several trunks. In Southern California most macadamia trees have been trained to a single trunk. From what I have heard from growers in northern California, many macadamias have several trunks and that mulit-trunk trees may have an advantage over single-trunk specimens, since if one portion of a tree is killed by frost, another trunk sheltered inside can survive. I suggest you contact a macadamia grower in your geographical area for advice on pruning your multi-trunk tree.

      Many years ago I did several television shows on macadamia trees. This came about because a grower who owned a large macadamia orchard contacted me and told me how to grow them, how to prune them and so forth. He also invited me to shoot my regularly-scheduled shows (on NBC news in San Diego) on his property, demonstrating how to harvesting nuts that had fallen, sun-dry them on wire-bottomed frames, crack the nuts, control rodents and so forth. Unfortunately that gentleman has now passed away. Currently I do not have a trusted advisor regarding macadamias. I suggest you contact a commercial grower near your residence or try to find a chapter of the rare fruit growers and ask the opinion of their members. You also may find people have a variety of ideas on the correct way to go on their culture, including pruning. One way to find a reliable expert is to contact your local farm advisor and ask him

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