The popularity of the tropical plants commonly called cannas (sometimes called canna lily) is no surprise to anyone who has ever grown these plants. From gnarled perennial rhizomes (not canna bulbs) emerge large leaves similar to bananas and gingers (sometimes colorful or stripped) and beautiful blooms in a variety of colors. When we gardeners in northern climates plant cannas in our gardens we usually plant the rhizome in the spring and summer and then lift it in the winter and store indoors. Propagating cannas is easy because all you need is a piece of the rhizome, but you can also propagate cannas from seeds if you know how to collect canna seeds.
Your canna lily flower will looks something like this, although there will be some variation in bloom size and color. No matter what the flowers look like the seeds will develop in the same place.
After the canna’s flowers have been pollinated the seed “pods” begin to develop along the stem. See the reddish pointy part that resembles a cone above the green orbs? That is where the flower petals where attached. The spiky seed pods of the canna just look dangerous and touching them won’t hurt you in any way.
When canna lily seeds have matured the green husk of the pod turns brown, shrivels and opens up. At this point if you were to press a pod between your fingers you’d be able to feel the hard seed(s) inside.
Inside each seed pod is at least two black, hard and shiny seeds. Seed pods that develop later in the gardening season may only have one canna seed per pod. These later developing seeds will also usually be smaller than the first seeds that ripen. I’ve not noticed that the smaller (or later) seeds germinate less or aren’t viable. The first thing you will probably notice in regards to these seeds is how hard the seed coat is; you could throw it against the concrete sidewalk and not cause a dent in the seed. Canna seed germination requires some kind of seed scarification to allow the embryo inside access to moisture. Over the years I’ve seen gardeners go to great lengths to get the seeds to germinate, from rubbing them with nail files to drilling holes in them with electrical tools. The easiest method I’ve come across is to submerge them in boiling water for a few moments until you hear them pop open.
While collecting canna seeds is extremely easy, because you don’t need to pollinate the blooms to produce seeds, because they’re so large and noticeable. While the seed harvest is easy the germination isn’t, and may be frustrating. Most cannas you’ll come across in garden centers are hybrids and seeds from hybrid plants will not produce plants that look like their parent. Also, the seedling will have to grow for a couple of years before their old enough to A) produce a decent-sized rhizome and B) flower. Although, sometimes growing a plant, even if not true from seed, is even more rewarding.
If you're new to seed saving check out the post "How To Save Seeds."