By Alastair Culham

A single tree of the brazil nut

Filling your lap with the sharp fragments of nut shells as you work through a bowl of shell-on nuts is one of the pleasures of Christmas.  Less fun is later treading on the sharp  fragments that have pinged across the room unnoticed.  The, sometimes, superhuman effort of cracking open the nuts is a sure sign the plant didn’t really want you to eat them.  One of the most challenging nuts to crack is the Brazil with it’s tough shell and almost no air space inside to allow movement.

Brazil nuts were the most exotic of the standard selection of mixed n seen for sale each Christmas in the UK. Hazel, walnuts and almonds can all be grown in the UK and around much of the rest of Europe however the Brazil nut really does come from Brazil and it has a fascinating biological story. The pecan has now replaced the brazil as the exotic nut of choice for a standard supermarket bag of mixed nuts due to fear of aflatoxins in the shell-on nuts but this is a poor second choice in my opinion. Shelled brazils are still readily available.

Brazil nuts used in teaching at UoR

The shape of a brazil nut brings to mind two adhering segments of chocolate orange and there is good reason for this.  The individual brazil is one of many segments formed inside a hard outer case.

Shelled brazils

To botanists the brazil is known as Bertholletia excelsa, a large tree (to 50m) naturally occurring in rainforest throughout Brazil, the Guianas and Venezuela, and in eastern Bolivia, Colombia and Peru.  It is an offence to fell brazil trees in Brazil due to their importance and the lack of ways to artificially propagate them. One of the fascinating interactions of the brazil is that with the Agouti which can chew through the hard shell of the fruit to release the seeds inside.  This is captured beautifully in a extract from The Private Life of Plants featuring David Attenborough, a series I was lucky enough to be involved with.

The need for Agouti is not the only close link with animals that the brazil tree has; its flowers are pollinated by female Euglossine bees whose males pollinate a particular orchid, so the brazil tree needs the orchid to be in the vicinity if it is to be pollinated.

Bertholletia is a member of the Lecythidaceae, a plant family including many tropical plants, some with extraordinary flowers.

Bertholletia excelsa in flower.

The story of the brazil is therefore one of complex interactions between plant, animals and environment.  There is a wonderful wordpress site devoted to the brazil where you can read a much fuller story of this wonderful nut. But the question remains; will we get our in-shell Brazil nuts back?  The answer is probably no – the cost of destruction of failed batches is high and research shows aflatoxins can enter the nuts if they are decomposing.


  • The Brazil nut story
  • Mori, S. A., Prance, G. T., 1990. Taxonomy, ecology and economic botany of the Brazil nut (Bertholletia excelsa Humb. and Bonpl: Lecythidaceae). Advances in Economic Botany 8, 130-150.
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