Sexual Reproduction and Early Plant Growth of the Wollemi Pine ( Wollemia nobilis ), a Rare and Threatened Australian Conifer

Abstract The two known populations of the recently discovered rare and threatened Wollemi Pine ( Wollemia nobilis Jones, Hill and Allen) consist of a small number of large multi-stemmed adult trees and small seedlings. Female and male cones are produced on adult trees with pollen release occurring in spring (October–November). Seed cones mature 16–19 months later in late summer and autumn and appear to be produced annually. Approximately 10% of seed produced in two consecutive years was viable, 25% of which was damaged by animals. Glasshouse studies showed that seed germination at 25 °C (day)/16 °C (night) proceeded slowly but steadily at approx. 4% per week until, after 6 months, 88% of apparently viable seed had germinated with the remainder of the seed rotting. Growth of potted seedlings in this temperature regime was continuous (after a lag period of 4–6 months) with the monopodial axis growing 0.05–0.25 m in the first year, 0.5–0.6 m in the second year and 0.25–0.35 m in the third year, attaining a total height of 0.8–1.2 m. Multiple orthotropic shoots developed on some plants at this stage, some of which outgrew the primary shoot in height. The diameter of the stem below the cotyledon (just above the soil) grew 3–7 mm in the first year, 10–14 mm in the second and 15–20 mm in the third at which time it was 25–34 mm. The average number of lateral branches produced was five–17 in the first year, 25–36 in the second year and 24–30 in the third year giving a total of 60–77. The establishment of Wollemi Pine in the wild does not appear limited by the inherent viability of seed and potential for early growth of seedlings.