In regions where winter temperatures dip below freezing (USDA hardiness zone 6 and below), it's essential to overwinter Canna Happy Isabel bulbs to protect them from cold damage. After the first frost, cut the foliage back to about 4 inches above the ground, then carefully dig up the bulbs, being mindful of the delicate roots. Shake off excess soil and allow the bulbs to dry for a few days in a well-ventilated area.
Store the bulbs in a cool, dark place, such as a garage or basement, with temperatures between 40-50°F (4-10°C). To prevent the bulbs from drying out, you can pack them in slightly moist peat moss or sawdust in a breathable container like a cardboard box or mesh bag. Check the bulbs periodically throughout the winter for signs of rot or desiccation, and remove any affected bulbs to prevent the spread of disease.
In warmer regions (USDA hardiness zone 7 and up) you can leave cannas outside. Add an extra layer of mulch in the wintertime.