It’s important to realise that plants rely heavily on humidity. Their roots draw water and nutrients up from the soil to the leaves. Evaporation of the water at the leaves, creates the suction for more water to be drawn up from the roots. If it’s humid, the water evaporation rate drops and the plant gets time for full synthesis of the nutrients. On hot dry days, the plant can reach a point where it cannot draw enough water through the roots. The evaporating moisture then draws water from the plant’s cells and they shrink, wilting the plant. The difference in humidity can create a much healthier plant, able to withstand hot weather. We keep humidity high by reducing the air flow, preventing wind from drying out the area.
However, some plants are prone to moulds, like zucchinis and cucumbers. To combat this we need a better air flow around the plants. Often trimming off some of the larger leaves can combat this but it pays to not plant these plants in a warm humid corner. Using shelter, you can create a whole range of climate conditions. In Melbourne I had a narrow strip between a high fence and the brick house, on the afternoon sun side. I planted a Tamarillo tree, that everyone said would die in the cold Melbourne frosty winters. It did exactly the opposite, fruiting prolifically on our side and the neighbours side of the fence. They complained about all the fruit until they saw it fetched $13.00 a kilogram!
Look at your block of land and plan your garden to utilise any micro-climate areas. Look for regions sheltered from winds by a fence. House walls on the sunny side of the building will act as heat banks, releasing warmth into the early evening after the sun has sunk below the horizon. Brick walls will still radiate warmth well into the night but they also absorb humidity. Areas near an outdoor hot water cylinder will be frost free in winter.