The first settlers to New Zealand had a problem. After travelling thousands of kilometres across the sea carrying them, their beloved Kumara (sweet potato) was having trouble adapting to the cold.
The cooler climates on NZ meant the plants were at the mercy of frosts and cooler ground temperatures. They early Maori didn't have greenhouses, or fancy irrigation systems, so they started by building some fences and walls around the plantations. This kept the wind out, but what they also realised was that stone walls had another benefit - they soaked up the warmth of the sun during the say, and radiated it back out in the evening, lengthening the period the crops were kept warm.