Canna bulbs are typically transplanted from an indoor location to the outdoors. However, they can be transplanted from one outdoor spot to another, if desired. Since canna bulbs--actually called tubers--are tender and not cold resistant, you should not transplant them when the weather is cold; they need to be brought indoors and stored during the cold weather until spring arrives.
Wait until after the last frost to transplant bulbs from winter storage. However, you must wait until the soil is at least 60 degrees F if you are transplanting cannas that were actually started indoors. Use a soil thermometer available at most nurseries if you are unsure of soil temperatures. Read the temperatures in several areas about six inches deep.
Prepare the planting site, if necessary. Dig a hole that is 2 feet deep and fill with water. If after 24 hours any water remains, you do not have soil that drains well and your canna bulbs may not survive. Therefore, add a couple inches of organic matter, such as compost, to the top 12 inches of your soil. This will make the soil more suitable for water drainage.
Dig up existing outdoor canna bulbs. If you are transplanting whole plants, carefully dig up the existing plants with the foliage. Cannas are typically planted just under the soil. Use a garden fork and dig a couple inches under the soil around the perimeter of the plants. Then pull down on the handle in several places so that the bulbs are lifted out of the soil.
Transplant the bulbs (and plants). Whether the plants are coming from another spot outside or from a potted plant indoors, you should plant cannas to the same depth as they were planted before. If you are only transplanting the bulbs, then plant them directly under the soil.
Push down on the soil around the plant to be sure there are no air pockets in the soil. Water the transplanted cannas and push down on the soil.
Keep the transplanted plants evenly moist for the rest of the growing season. After the first frost, dig up canna bulbs and store in a warmer location if you want them to grow again the next year.