Is it OK to leave canna lilies in the ground over winter? And when they are done blooming what are the funky looking little balls where the flowers used to be? They are filled with very hard black balls. Are these, or any part of the plant poisonous?
Canna lilies are hardy in zones 8 to 11. That means gardeners in colder zones need to treat them like annuals or move them indoors for winter. Northern gardeners can save their cannas from year to year by storing the rhizome, thick fleshy root-like structure, in a cool dark location. Dig the plant in fall after a light frost. Set it in a warm dry place to cure. Gently remove any soil and cut off the foliage. Pack in peat moss or sawdust and store at 45 to 55 degrees.
The funky looking balls are seed pods. The hard round things inside are seeds. These black seeds are so hard that the West Indies natives used them as shot giving these plants another common name Indian shot. One of the ornamental cannas’ relatives the Queensland Arrowroot (Canna edulis) was used as food and is an ingredient of arrowroot starch. I wouldn’t recommend munching on your cannas but I could find no reference stating they were poisonous.