I just purchased a bunch of red canna bulbs to plant in my gardens. In Louisville, when is the right time to plant them? Should I be concerned about frost occurring if plant prior to the Kentucky
Derby date? I also purchased lily of the valley and plan to grow them in a huge shady area as a groundcover. Is April okay to plant them, or should I wait until after the Derby?
The Gardener’s Answer
Hello, Charlotte: We are zone 6 here in Louisville according to the USDA hardiness zone map. There has been some debate recently that the metro area may now be zone 7 but nothing is confirmed yet. As for your canna lily bulbs, you do want to wait until Derby to put them in the ground. Our frost-free date is May 10. Cannas are considered a tropical for us, so we need to wait until the danger of frost has passed to plant outdoors. You can dig the bulbs up in the fall and put them in a paper bag to store them for the winter. Keep the bag in a cool, dark space like a closet and bring them back out the following spring. Lily of the valley (Convallaria majalis), on the other hand, is a hardy perennial for those of us gardening in Kentucky. You can go ahead and plant anytime now. This is a great option for a shady groundcover. The fragrant white blooms are very sweet and the foliage will remain green throughout the growing season. It will tolerate a dry site once established, but try to keep the soil evenly moist this summer. Lily of the valley is a spreading perennial, so make sure to plant it where it is free to do so, otherwise you will find yourself digging it out of a space where you did not intend for it to grow.