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Nut tree growing guide
Brazil nut is one of the hardest nut trees to grow from seed: intact seed can take more than a year to sprout, and the tree needs a hot, wet tropical climate. With fresh seed, patience and a careful method it can be done, and this guide explains how.
Use fresh, raw seed in its woody coat and never let it dry hard. World Agroforestry classes the seed as intermediate in storage: drying from 14.2% to 4.2% moisture cut viability from 60% to 2%, and seed stored openly at room temperature gave only 3% germination after 18 months. An Embrapa study found that storing seed in moist sand for up to 180 days kept it viable.
This is the key step. Removing the woody seed coat speeds germination from 12-18 months to around 20 days in an Embrapa report. Chemical soaks did not help: in a 1984 Embrapa trial acid and other chemical treatments gave no better emergence than untreated seed, and acetone killed the embryos. In a nursery method from the Peruvian Amazon (IIAP, Puerto Maldonado), seed was first kept about five months in moist substrate in sealed buckets under 50% shade, which softened the coat; the coat was then removed with a knife and vice, taking care not to wound the kernel.
No cold treatment. The moist, warm storage described above is the only conditioning used.
A short soak before opening is optional; do not use gibberellic acid, which cut germination from 82% to 36% in an Embrapa study.
No precise laboratory optimum is published for home growers. Keep seed warm and humid all the time, as in its Amazon home with mean annual temperatures of 24-27 °C (75-81 °F). In India this means the humid coastal tropics; elsewhere a heated greenhouse or propagator.
About 1 cm (1/2 in) for seed with the coat removed; Embrapa also sowed intact seed upright about 1 cm deep.
In the Peruvian trial forest soil, sand, sawdust and sand-sawdust 1:1 all worked (71-81% normal seedlings, no significant difference), with sand mixes giving the strongest seedlings. Use a clean, free-draining mix at least 15 cm (6 in) deep.
Evenly moist, never soggy. Opened kernels are prone to mould, so growers treat them with a fungicide before sowing.
Germinate under about 60% shade, as in the Peruvian trial; avoid direct sun on the tray.
In the Peruvian trial, coat-removed seed reached about 40% by day 15 and about 81% by day 30. Intact seed takes 12-18 months according to earlier Brazilian work, although some sprouts may appear from about three months.
Move seedlings into deep nursery tubes or pots at about 40 days, as in the Peruvian trial, handling the root carefully. Grow on in partial shade and humid air.
Protect seedlings from rodents and leaf-cutting ants, which World Agroforestry lists as seedling pests. Plant out in a deep, well-drained but moisture-retentive soil; the species tolerates heavy clay and poor Oxisols but not waterlogging.
Brazil nut grows in warm, wet lowland rainforest with 1400-2800 mm (55-110 in) of annual rain. It will not thrive in subtropical or dry regions.
Plantations space grafted trees 10 x 15 m or 20 x 20 m (33 x 49 ft or 66 x 66 ft); a seedling needs similar room.
Fruiting starts at 12-16 years in forest and from about 8 years for well-managed trees in the open, and flowers need large bees to set nuts.
Even with the best method a share of seed fails, so start more than you need.
A long-term project for tropical growers: sow fresh Brazil nut seed with patience and warmth.
Rarely. Shelled kernels are often damaged or dried hard, and dried seed loses viability quickly. Use fresh seed in its woody coat.
Intact seed usually takes 12-18 months. With the woody coat removed, seed in a Peruvian trial reached about 81% germination in 30 days.
Only in the hot, humid lowland tropics with heavy rainfall and no cold season, such as the wettest coastal regions, or in a heated greenhouse elsewhere.
Possibly, but only after about 8-16 years, and only where large bees visit the flowers.