For its first seven or so years, yes, tawa is very slow growing. Unlike taraire, it seems to require strict shelter from wind and frost, and a partially shaded situation. It is a lovely tree, but does best in a well-watered rainforest habitat and is fussy about soil conditions. It has a radial root system and seed is best sown directly into very deep containers (like avocado root trainers). A big clue to its successful establishment lies in an intact and undisturbed tap root.