Four- and five-year-old plants gave a distinctly higher yield of seeds in comparison with six-year-old plants. Seeds originating from younger plants were also characterised by higher individual weight. Germination ability of seeds was affected both by age of mother plants and by temperature and presence of light during germination process. Higher germination ability and higher weight of seedlings was observed at substrate pH 5.5 and 6.5 in contrary to pH 3.5.