Germination and Vitality of Birch Seeds

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Abstract
The germination of freshly harvested seed of Betula lenta was poor, but improved with dry storage. Air-dried seed ''had a narrow temp. range for germination, the minimum being 30[degree] C. for B. lenta, and 20[degree] C. for B. populijolia, B. papyrijera, and B. lutea. The optimum temp. for all sp. was 32[degree] C. or 15-32[degree] C. alternating. After-ripening proceeded best at 0-5[degree] C. and caused a lowering of the minimum temp. required for germination. Stored moist at this temp. 4-6 weeks was sufficient to bring about excellent germination at 15[degree] C. After a storage of 5-6 mo. at 0[degree] C. germination occurred at 0[degree] C. Freezing was ineffective or injurious. Germination was not affected by degree of acidity, light intensity, CO2 concentration, or partial pressure of O. B. papyrijera was the first to lose viability on storage. Its optimum H2O content for storage was 0.6%, that for B. populifolia 5.2%, while B. lenta kept well in all but very humid conditions. Viability was retained better when stored in an ice chest, irrespective of moisture content. The best time for harvesting was after the catkins had dried on the tree, but before they had opened. In making the tests, wings were removed from the seed. Conclusions are based on tests of about one million seed. The importance of after-ripening treatment in enabling the seed to germinate promptly in the early spring is pointed out.

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