The Treasure Valley is known for its dramatic diurnal temperature swings—warm, sunny winter days followed by rapidly freezing nights. For young trees, especially those with thin, smooth bark like Honey Locusts, Lindens, and young Maples, these fluctuations can cause severe structural damage known as Winter Sunscald or Southwest Injury. During clear winter afternoons in communities from Star to Meridian, the low-angled sun aggressively heats the south and southwest sides of a tree trunk. This localized warmth prematurely breaks the dormancy of the cellular tissue (the cambium layer) just beneath the bark, causing water to move into these cells. As the sun sets and temperatures plummet below freezing, this water rapidly freezes and expands. The resulting cellular rupture causes the bark to split, crack, and eventually peel away. These vertical fissures permanently damage the tree’s vascular tissue and create open entry points for opportunistic insects and wood-decaying fungi. Homeowners can prevent sunscald by wrapping the trunks of newly planted trees with a breathable, reflective tree guard in late autumn, ensuring the wrap is removed in early spring to prevent moisture retention and fungal growth.