Yes, native plants need supplemental water until their roots have become established enough to support the plant – which usually takes from 2 to 3 years. In the wild, a native plant has a root system that is at least 10x as big as its above-ground stems. Native plants grown in a nursery have spent their young lives fully provided for, so their root systems have not needed to spread far to find sustenance. Once planted, it takes time for their roots to spread far and deep enough for the plant to take over its own care.