Our Perennial Mum Plants have shown to exhibit reliable hardiness. Hardiness can be assured by proper care, which includes keeping the soil moist, planting in a sunny location, fertilize often, trim back to within 4-6 inches from the ground after Thanksgiving, and apply a protective covering of mulch after the ground has frozen. Minnesota perennial mums should be divided every 3 years. Our Perennial Mum plants for sale are shipped with very well-established root systems. We guarantee them to arrive alive and thriving. They start shipping the first of June.