Brazil Nut

Bertholletia excelsa (nobilis)

Origin:

The Amazon forest regions of South America. It is the only species in the genus.

Climate:

Lowland humid tropical regions up to altitudes of 500m, with rainfall of 2000-3000mm pa, mean daily temperature of 27-32°C and humidity of 80-90%.  A substantial dry season is necessary to induce flower formation: Brazil nuts grow naturally only in regions with a three-to-five-month dry season. They are intolerant of waterlogging.

Plant Description:

In their preferred environment, these majestic canopy trees are long-lived, up to 500 years, and can become enormous, up to 60 m tall. They are fast-growing and semi-deciduous in extended dry periods with a straight trunk having a diameter of 1-2m; branching only begins high up.  The large oblong leaves are alternate, simple, coriaceous and glabrous, 20-35 X 10-15cm. They are reliant on a very specific ecosystem.

Relatives:

Lecythidaceae Family, related to paradise nut, cut-nut, membrillo and monkey-pot nuts. Also distantly related to mangroves.

Soils:

They will grow on sandy clay or clay soils provided they’re well-drained.

Propagation:

By seeds and grafting.  Seeds can remain viable for 12 months.  The species illustrates the large influence of inhibitory factors in maintaining seed dormancy, in this case from the integument.  Intact seeds may take 6-24 months to germinate whereas when the integument is removed it may be only 25-30 days. Seeds are often prepared for sprouting by a series of intermittent soakings, to simulate conditions in their native jungle.

Cultivars:

Almost all world production comes from wild trees, but in some tropical countries, driven by their superb nutritional properties, efforts have been made to select superior trees. Unfortunately you will inevitably never see these for sale in your friendly local Nursery.

Flowering and Pollination:

The small creamy-white hermaphrodite flowers, 5cm wide, are borne mainly on terminal upright panicles, 20-40cm long.   Each flower has 2-4 sepals, 4-6 unequal petals, 80-130 stamens joined on the lower side of the flower and an inferior ovary with 4-5 locules, each containing 5 ovules.  Flowering occurs during dry periods and cross-pollination is necessary for good yields.  Flowers open early in the morning and are only open for a single day.  Various species of bees are the main pollinators.  While there is massive flowering, fruit set is usually less than 1%; lack of effective pollination is the usual cause of lower set.

One of the main problems they encounter is that pollination is difficult outside the proper ecosystem where the principal pollinators are large female bees that are strong enough to get through stiff flower staminodes. Male bees are attracted to an orchid that does not grow on brazil nut trees, but on nearby trees. The orchid produces a scent that the male bees need to attract the females. Without the orchid, the bees do not mate and the flowers do not get pollinated.

The bees are also dependent on certain other plants that provide them with pollen and nectar during the times when the brazil nut trees are not flowering. The successful plantations have worked out the auxilliary species they need to interplant with the brazil nut trees.

Cultivation:

As a canopy tree, they need full sun.  There are a few successful plantations, mainly in Amazonia but also in other tropical countries. No systematic studies have been reported on nutritional management.

Wind Tolerance

Very good.

Pruning:

These trees are genetically programmed to be large, so no matter what size containment pruning is undertaken, they will still need lots of space.  Training with the aim of increasing lower branching should not be done for the first 2 years.

The Fruit:

The fruit is a large globose woody brown capsule with a thick shell, 10-15cm diameter, weighing 0.5 2.5 kg, and containing 12-25 3- angled seeds, 3-7cm long, with a thick brown seed coat and an edible white kernel.  These kernels are nutrient dense, having 14% protein, 66% lipids, 12% carbohydrate, 7.5% fibre, excellent levels of Ca, Mg, Zn, Cu and Mn and the highest level of selenium produced by edible plants.  Most of the lipids are the healthy non-saturated types.

Fruit Production and Harvesting:

Seedling trees may take 6-20 years to bear fruit and grafted plants 3-6.  Fully mature production will gradually be attained over the following 20 years. Alternate bearing with a 2-3 year cycle is common.  Fruit have a long maturation period of 15 months.  Fallen capsules are normally gathered from the ground and must then be opened and seeds dried promptly to avoid dangerous mould growth.   Good yields of 300kg of in-shell nuts have been reported in favourable conditions for some trees.

Fruit Uses:

Brazil nut is eaten fresh and better still with roasting to enhance the flavour.  They’re also used in various processed forms such as pastries, gruels, breads and flour and ice creams.

Comments:

Brazil nut trees in their native territory are disappearing at a great rate due to the opening up of the region to agriculture and logging. They do not regenerate naturally after the forest has been cleared and burned. It is not easy to obtain seeds that will germinate. Some have been steamed to kill mould, and others boiled before sale.

At least 3 major issues need to be considered in attempting to grow this species in south west WA – their size plus their essentially self-incompatible habit, the presence of effective pollinators, and the need for almost continuous humid tropical conditions.  If you ever take on the challenge and succeed with nut production here, we’ll petition for a national holiday and hero status!

Seriously though, they are not recommended for Perth or surrounds but it might be doable in the Ord.

More Brazil nut info: Brazil nuts to the rescue?