Growth habitGrowth habit

Growth habit

Wollemi Pine produces three types of shoots:

 Juvenile and lower canopy plagiotropic shoots: this type of shoot forms the lateral branches on juvenile Wollemi Pine or in the lower canopy on adult trees. This shoot is horizontal, and leaves begin as short scale-like leaves only 3 mm long but grow to 20–80 mm long and 2–5 mm wide. Leaves are linear to narrowly triangular, opposite or subopposite and grow in two opposite ranks (Jones et al. 1995).

 Adult orthotropic shoots: this type of shoot grows vertically and includes the primary trunk and additional, subsidiary vertical shoots which develop from the trunk or adventitiously arise from just below the cotyledons (Burrows et al. 2003). These shoots exhibit a helical arrangement of leaves, which are small, only 3–10 mm long and 2–4 mm wide at the base, taper to an acute angle at the tip, have a sharp point and are narrowly triangular (Jones et al. 1995). Primary branches arise at the apex of these vertical shoots and are plagiotropic (lateral) and short-lived.

 Adult upper canopy plagiotropic shoots: this type of shoot forms the lateral branches of adult Wollemi Pine, primarily in the upper canopy. Initially these branches grow nearly vertically, before becoming horizontal and later pendulous. Leaves begin as short scale-like leaves only 3 mm long but increase to 10–40 mm long and 4–8 mm wide (Jones et al. 1995). Leaves are narrowly oblong, opposite or subopposite decussate (each opposite pair occurs at right angles to the previous pair) and longer leaves are twisted at the base, giving the appearance of four flattened ranks of leaves (Jones et al. 1995; Chambers et al. 1998). Male (pollen) and female (seed) cones can develop at the tip of these branches when the branches are between 1 and 10 years of age. Typically, female cones occur on higher branches of the same trunk than males, which is thought to promote greater outcrossing (Jones et al. 1995, Hill 1997, Offord et al. 1999). After initially bearing cones, branches may continue to grow vegetatively and produce further cones. Branches grow for up to 11 years before cleanly abscising (Burrows et al. 2007).

The combination of these three shoot types, along with regular self-coppicing, from both the base and epicormically in undamaged individuals—an unusual trait for a member of the Araucariaceae family—contribute to the Wollemi Pine’s unique growth habit (Burrows et al. 2003).