PHOENIX (AZFamily) — An unusual March heat wave is stressing local plants, and a gardening expert says the key to keeping them alive comes down to how you water, not how often. Michael Overstreet, who goes by “The Garden Nerd,” said plants are showing visible signs of heat stress this time of year because they are not accustomed to high temperatures this early in the season. “The reason you see them struggling is because they’re not used to this much heat so early in the season,” Overstreet said.