Tanekaha is a medium-sized forest tree growing up to 20 m in height and 1 m trunk diameter. The main structural shoots are green for 2–3 years, then turn brown as the bark thickens. The leaves are sparse, tiny, scale-like, 2–3 mm long, and only green (photosynthetic) for a short time, soon turning brown.
Most photosynthesis is performed by highly modified, leaf-like short shoots called phylloclades; these are arranged alternately, 10-15 on a shoot, the individual phylloclades rhombic, 1.5-2.5 cm long. The seed cones are berry-like, with a fleshy white aril surrounding but not fully enclosing the single seed.