Plant Doctor Archive

What's eating my macadamia nuts?

WE'VE just moved on to a property that has three macadamia trees about 4m high, in a row down the side of the house. There are some nuts on the trees, but others on the ground have holes in them. Do you know what makes the holes and should we prune the trees, as they are very bushy and taking up a lot of space?

THE most likely culprits causing holes in the nuts are rats. They'll even climb the trees to eat them - the macadamia's tough shell is no match for a rat's sharp teeth. You'll either have to set traps or use bait, such as Talon, which you can buy at supermarkets or hardware stores. Follow the label recommendations, especially to avoid dogs and cats eating the bait.

Macadamia trees can grow quite large, around 8m or more high and wide when mature and generally need little pruning, but given the confined space, you'll have to do something to restrict their size. I suggest you wait until spring, then trim off the lowest branches, cutting them right back to the trunk to reduce the spread. At the same time, thin out a few branches from the upper part of the trees to allow light into the centre of the trees, and if necessary trim back any particularly wide-spreading branches. Alternatively, you could just trim them into a neat hedge. Either way, you won't harm the trees. Unfortunately, the more you prune and trim, the fewer nuts they'll produce, but you should still get some and their foliage is quite attractive anyway.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.