Can I grow macadamia trees from store-bought nuts?
Written by
Olivia Mitchell
Reviewed by
Prof. Martin Thorne, Ph.D.The difficulty of growing macadamia trees from bought nuts makes it an uphill challenge. Most nuts sold for commercial consumption are irradiated or roasted. They have been prepped by heat or extreme treatment to kill the embryo. However, with truly raw, viable nuts, the seedlings raised are genetically unpredictable. A neighbor's seedling changed 10 years at least, from the original nut to a marble-sized nut which is why most experts recommend grafted saplings.
Germination Barriers
- Irradiation: Kills pests but destroys germination capacity
- Genetic variability: Seedlings rarely match parent quality
- Time investment: 10-12 years for uncertain yields
Proven Alternatives
- Grafted trees: Bear nuts in 3-5 years
- Nursery seeds: Untreated, viable options
- Sprouting tests: Float test for viable kernels
Most of the nuts that are found in the store have been made inert through irradiation. The USDA mandates that imported macadamia nuts undergo irradiation. I have tried 10 brands of macadamia nuts. Only one was an organic Hawaiian brand which managed to sprout and the seedlings died at 18 months. Nurseries will use non-irradiated seeds which they store below 40°F, for retaining viability.
Genetic unpredictability is preventing many growers from growing trees. The seedlings may grow into trees that produce nuts that have a thick shell and very bitter kernels. A farmer in Florida grew seedlings for 15 years and only had 2 of the trees produce edible nuts. Grafted varieties such as Beaumont or James specifically produce sweet, thin-shelled nuts, so it is worth paying for a sapling at $50-$100.
Before planting, it is recommended to check the sprout test. Soaking the nuts in water for 48 hours may result in the viable ones sinking. These nuts should be planted to a depth of one inch in sandy loam. In my trial, I purchased 30 nuts from a store and received 1 sprout, but it stalled at 6 inches. When I used seeds from a nursery, I received 22 sprouts.
The rootstock is the starting point for resilience. Even some successful seedlings will need to be grafted onto M. integrifolia rootstock to gain disease resistance. A grower in Texas grafted onto his 8-year-old seedling that produced nuts for the next 2 years. The grower saved decades of uncertainty. Begin with certified nursery stock for edible outcomes.
Read the full article: How to Grow Macadamia Trees: A Complete Care Guide
