Te Taiao (the environment) on Mokoia Island in Lake Rotorua was ideal for growing kūmara. East facing plantations exposed the kūmara to all day sun and provided a natural shelter-belt from the harsh westerlies, while the thermal heat made it possible to grow kūmara all year round. The island’s volcanic soil was an ideal medium, the sand at the lake’s edge would have been great for growing (tipu), and the water of course was pristine.
Matuatonga (our sacred deity) arrived from Hawaiiki on Te Arawa waka and was taken to its resting place on Mokoia Island originally called Te Motu-tapu-a-Tinirau. The ability for kūmara to grow so well on Mokoia was attributed to the powers of Matuatonga. This power could perhaps be described as the celestial link of the kūmara to its humble spiritual beginnings. Mokoia Island was tapu (sacred) with the presence of Matuatonga which is still there today. Before each planting ceremony, tohunga (scholar) took their seed-kūmara to the island and touched Matuatonga, thereby gaining its mana (power).
Source Kai Rotorua – discover more about the significance of Kūmara here.