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Both the
P. koraiensis and
P. pumila are known for their slow growth.
I would think that the Korean variety would be better for pine nut harvesting:
The Siberian has +/- 10,000 seeds per pound, while the Korean has +/- 800 seeds per pound.
One would provide you with true nuts, whereas the other would be more like a 'nut meal' in texture.
St. Lawrence Nursery suggests adding humus from other pine trees around the base to help with the growth rate.