Karen Mitchell, consumer horticulture extension specialist, reassures gardeners in an Indy Star article, “Here’s what Indiana’s sub-zero forecast means for your garden.” Mitchell emphasizes the resilience of Indiana perennials to extreme cold, but mentions that winter injury may occur and should be assessed in April and May. She advocates a proactive prevention strategy for protecting plants from winter injury, such as keep plants well-watered until the ground freezes and maintaining mulch to a depth of 2-3 inches.