If the temperature is expected to be 20° to 35°F in your area during the time your plants will be in transit, then we recommend you add some UniHeat Shipping Warmers to your order. Shipping Warmers really help prevent freezing during shipment. Here’s how to tell how many shipping warmers to put in your order. For 7-11 plants add one warmer. For 12-23 plants add two warmers. For every additional 20 plants add two more. If the temperature is expected to be below 20°F, then you should also ship your plants using UPS 3 Day Select. At this temperature it’s just too cold, even for the warmers. We recommend using this faster shipping with signature required so your package does not sit outside in the cold. Be prepared to track and receive your order. We are not responsible for freezing during shipping.