Planting and Growing Cannas (Canna Lilies)

Watering

Cannas need wet soil. If the soil doesn’t remain moist, provide a good soaking once a week and every other day during the hottest weeks of summer—water freely in dry spells. Maintain a thin layer of mulch to help retain moisture.

Fertilizing

Where the soil is fertile, fertilizer is optional. However, cannas are big eaters and would benefit from slow-release fertilizer at planting and twice during the growing season. Fish emulsion fertilizer, which is a little higher in nitrogen, is a beneficial organic alternative. Higher nitrogen fertilizers tend to increase canna height. Rose or tomato food products are also suitable.

Deadheading Cannas

• To promote blooming, check your canna every few days to deadhead (i.e., remove spent flowers).
• When deadheading, use small garden pruners or scissors. Do not pinch with your fingers.
• Canna stems grow several flowers on a single stem. Snip off only the spent flower where it joins the main stem, leaving the other spikes to continue to bloom.
• Once all the flowers on a single canna spike have bloomed, you may cut that part of the stem back, but avoid cutting off any new budding spikes.

Cutting Back and Pruning Cannas

After the entire plant has been deadheaded several times and with flowers no longer forthcoming, cut the flower stem back to the foliage. 

Only at the end of the growing season should you cut the plant—down to around 6 inches off the ground. 

If the plant looks “trashy” or the leaves get sunburnt, however, you can simply trim off the brown edges (like a haircut) or trim off any dead leaves at the bottom near the stem. 

Be careful not to nick the main stem. If the stem is damaged, cut it back to the ground.

You may see seed pods on your canna! These seed pods will make more cannas, so you can clip them off and put them right in the soil of your cannas; it may take a few years to get going, but you’ll have more cannas in the future.

How to Store Cannas for Winter

In Zones 7/8 and warmer, cannas can be left in the ground year-round. After frost kills the foliage, cut in-ground plants back to 4 inches. Add a healthy layer of straw or leaf mulch in the fall to protect rhizomes from the cold as the plants overwinter in place. (Note: Zone 7 doesn’t always experience canna-killing winter temperatures, so it’s a judgment call.) 

Bring cannas grown in pots indoors into a garage or basement for winter. Keep them dry (do not water) until spring’s nighttime temperatures are consistently above 50°F, typically after the tulips have bloomed in northern areas. Only then move them outside for the summer.

In Zone 6 or colder, it is necessary to dig up (lift) in-ground cannas in the fall and bring them inside for the winter. After cutting the canna back (as above), dig out the rhizome with a shovel. Avoid damaging the rhizome by digging about 1 foot away from the stem. With your hands, gently loosen the soil and lift out the clump. Shake off the soil and cut off any foliage. Divide clumps into 3 to 5 rhizomes, each with eyes.

Cure the rhizomes in the sun or in a garage or closet for a few days to toughen them up and help them resist rot. Wrap each rhizome in a newspaper or a paper bag, along with a small amount of dry growing medium, such as peat moss, to absorb moisture and prevent rot. Rhizomes should not touch each other.

Store cannas over the winter in a dry place where the temperature will not drop below 40ºF. Often, this is a basement, attic, or garage. Check the rhizomes a couple of times over the winter to make sure that they don’t dry out. Mist with a bit of water, as needed. If you find rot, trip it away or discard the entire rhizome. 

When spring’s nighttime temperatures are consistently above 50°F, replant outdoors. Make sure each divided piece has at least one eye; from it, new leaves will grow. Blooms should appear in 10 to 12 weeks.