Another couple of important crops were already in Aotearoa when Maori arrived - the cabbage tree and the gourd. The cabbage was so abundant it just wasn't worth the effort of cultivation and became a foraged crop.
Both the green shoots and the stem were eaten, the stem a particularly special sweet treat when cooked long and slow in custom-built ovens called umu ti. The gourd was cooked hangi style and eaten when it was young.
Older fruits were hollowed out to carry water, oils and birds, which were preserved in their own fat.
More supplementary foods were foraged including karaka berries, which, fortunately, underwent a special process to leach out the poisons (imagine being the poor sap who had to figure that one out), poroporo (shrubs with edible fruits), para (ferns with edible roots) and rengarenga lilies, which have edible rhizomes.
Bracken fern roots (rauaruhe) were also eaten, often as a stop-gap between other crops. None of these sound too fetching from a culinary perspective but I imagine it was just a matter of survival until the next kumara harvest or moa hunt.
Maori also introduced many of the gardening techniques employed by other major agricultural cultures such as the use of canals and ditches to avoid surface flooding, raised beds, terraced and sunken gardens using dry stone walls. Large areas, which were known as "swidden" gardens in England, were intensively planted and abandoned once the land became unproductive.
Once Europeans arrived most of the traditional crops and centuries-old garden practices were kept and many new ones were adopted, putting Maori in the agricultural driver's seat, as long as they had the land.