Cutting back cannas is simple: once frost has blackened the leaves, the stems come down to a short stub. The cut itself matters less than what happens to the roots afterward, because cannas don’t survive hard freezes. Whether you cut to about 6 inches (15 cm) and mulch in place, or cut to about an inch and lift the plants for storage, depends on whether your winters let the plant stay in the ground.
When to Cut Back Cannas
A canna grows from a rhizome, a thick underground stem that stores food for next year, a bit like a ginger root. In the last weeks of autumn the plant moves nutrients from its leaves down into the rhizome, which plumps it up and helps it survive winter.1Longfield Gardens. Can I Dig Up Canna Bulbs Before the First Frost? Expert Tips A light frost tells the rhizome to go dormant, and once the leaves turn brown or black the plant stops growing.2Longfield Gardens. Can I Dig Up Canna Bulbs Before the First Frost? Expert Tips Cutting green leaves early cuts off that last top-up of stored energy.
Frost-touched leaves go limp, then turn brown or black within a day or two. The flowers collapse and the tops of the stems may soften. If the whole plant is limp and discolored after a night or two, it has been killed back and cutting is safe.
Frost-damaged leaves may still send a little more energy to the rhizome.3Garden Ninja: Lee Burkhill Garden Design. Cannas should I prune them back before winter or leave their leaves intact? The difference is small, so there’s no need to wait long after frost. RHS advice is to act once the top growth begins to wither in autumn.4RHS. Canna Plant Care | RHS Advice
If frost hasn’t come yet, in a mild autumn you can wait until the leaves yellow and wither naturally. In colder areas, watch the forecast so you lift before a hard freeze reaches the soil.
How Far Down to Cut the Stems
RHS advice is to cut foliage and stems down to about 15 cm (6 in).5RHS. Canna Plant Care | RHS Advice Others cut the flower and leaf stalks to about an inch above the rhizome, using sharp, sturdy pruners.6Bunny’s Garden. Overwintering Cannas – Cutting Back, Lifting, Storing, Plus Tips Either works.
Cut each stem straight across rather than tearing it. Clear away the cut leaves, since they can harbour rot if left lying around. Compost healthy foliage, but bin anything spotted or mushy.
Choose the taller stub if the plant is staying in the ground, because it marks the spot and keeps you from digging into the clump when you plant other things. Choose the shorter one if you’re lifting and storing, because there’s less stem in the way when you pack rhizomes into boxes. If you’re undecided, cut to about 6 inches first. You can always shorten the stubs after lifting, but you can’t put stem back. Cutting all the way to soil level is a common mistake: it leaves nothing to grab when lifting, and hollow stems cut flush can let water in toward the rhizome.
Leave Them in the Ground or Dig Them Up
Canna rhizomes are damaged by freezing at just a few degrees below freezing, around -3°C (27°F).7Acta Horticulturae. Evaluation of Freezing Hardiness and Low Temperature Exotherm of Ornamental Geophytes Unlike some hardy bulbs, cannas don’t toughen up as autumn gets colder.8Acta Horticulturae. Evaluation of Freezing Hardiness and Low Temperature Exotherm of Ornamental Geophytes
In Zone 7 you can often leave cannas in the ground under 6 to 8 inches of straw or leaf mulch.9Longfield Gardens. How to Overwinter Canna Bulbs: A Step-by-Step Guide In mild UK areas they can stay out all year in a sunny, sheltered spot under a 15 cm (6 in) layer of mulch, though you should expect some losses in very cold or wet winters.10RHS Advice. Canna Plant Care Any organic mulch works, such as compost, manure or composted bark.11Cool Tropical Plants. Overwintering canna plants
Spread the mulch right after cutting back, covering the whole clump plus a margin around it. In spring, pull the mulch back once frost risk passes. In Zone 6 or colder the ground usually freezes too deep for mulch to protect the rhizomes, so lifting them is the safest choice.12Longfield Gardens. How to Overwinter Canna Bulbs: A Step-by-Step Guide To decide if you’re mild enough, check your USDA zone or local frost depth.
Cold is only half the danger. Rhizomes sitting in cold, waterlogged soil can rot even if the temperature never drops far below freezing. Heavy clay holds water around the rhizome all winter, so the same mulch that protects a plant in light soil may not save one in clay. If your bed is wet in winter, lifting is the safer choice even when your zone says you could leave them.
Lifting and Drying the Rhizomes
After cutting back, lift the rhizomes and remove excess soil.13RHS. Canna Plant Care | RHS Advice Start with a fork a hand’s width out from the clump, and lever from several sides before lifting so you don’t spear the rhizomes. Label varieties as you lift them. Trim off any soft, mushy or damaged sections; healthy rhizomes feel firm like a fresh potato.14Longfield Gardens. How to Overwinter Canna Lily Bulbs: A Simple Step-by-Step Guide Broken pieces are fine to store if they’re firm.
Leave small clumps of dry soil, because forcing it off can scrape the skin. Rinsing adds moisture right when you want the rhizomes to dry, so if you do wash them, allow extra drying time.
Curing means letting the rhizomes air-dry before storage so the outer skin toughens.15Longfield Gardens. How to Prepare Canna Bulbs for Winter Storage: 5 Easy Steps Dry them in a well-ventilated area at 70 to 80°F (21 to 27°C).16NYBG Plant Information Service. How do I prepare my canna for winter storage? About one week is usually enough, and a ventilated garage or closet works well.17The Spruce. How to Dig Up and Store Canna Bulbs for Winter Curing is done when the skins feel dry and slightly papery, not damp, and the cut ends have sealed over.
Storing Cannas Over Winter
Store rhizomes in trays of barely damp multi-purpose compost.18RHS. Canna Plant Care | RHS Advice Or wrap each one in newspaper or a paper bag with a little dry peat moss or vermiculite, which soaks up moisture.19The Spruce. How to Dig Up and Store Canna Bulbs for Winter Put the wrapped rhizomes in a cardboard box and keep them from touching each other.20The Spruce. How to Dig Up and Store Canna Bulbs for Winter Label the box with the variety and the date, because varieties are hard to tell apart once the stems are gone.
Keep them somewhere frost-free.21RHS. Canna Plant Care | RHS Advice Storage around 1 to 4°C (34 to 39°F) with protection against water loss looks best for long storage.22Acta Horticulturae. How to Cut Back Cannas for Winter Still, anywhere between 1 and 13°C caused no harm over five weeks.23Acta Horticulturae. How to Cut Back Cannas for Winter An unheated basement or garage that stays above freezing works, and little if any watering is needed.24RHS. Canna Plant Care | RHS Advice
Heated rooms dry rhizomes out too fast. Plastic bags trap moisture and invite rot, and boxes should stay off cold concrete floors.
Preventing Rot in Storage
Open the boxes once a month and look for rot and severe drying.25Longfield Gardens. How to Overwinter Canna Lily Bulbs: A Simple Step-by-Step Guide Remove any mouldy or soft rhizome right away.26Longfield Gardens. How to Overwinter Canna Lily Bulbs: A Simple Step-by-Step Guide If the damage is small, cut it out and let the piece dry before returning it; if the rhizome is mostly mushy, throw it away.27Longfield Gardens. How to Overwinter Canna Lily Bulbs: A Simple Step-by-Step Guide If rhizomes look wrinkled, mist the medium lightly.
Soft rot makes a rhizome feel squashy and look dark or watery, and it often smells bad. Mould shows as fuzzy white, grey or green patches on the skin or in the packing material. A little surface mould that wipes off a firm rhizome is less serious than soft, spreading decay, but it still tells you the box is too damp.
Fungicide-treated rhizomes had far less disease in storage and sprouted far more often.28Elsevier (Scientia Horticulturae). Effect of six pre-storage rhizome treatments on rhizome vitality and seasonal growth characteristics of three Canna × generalis cultivars29Elsevier (Scientia Horticulturae). Effect of six pre-storage rhizome treatments on rhizome vitality and seasonal growth characteristics of three Canna × generalis cultivars If you’ve lost cannas in storage before, a fungicide dip is worth trying.
Follow the product label for dilution and gloves. Dip after cleaning, then let the rhizomes finish curing. Charcoal dust did little in testing, so don’t rely on it.
Cannas in Pots
Potted cannas can simply be moved into a cool, dry area for winter.30Epic Gardening. How to Overwinter Canna Lilies in 6 Simple Steps No lifting or curing is needed, and you keep the compost nearly dry, as for stored rhizomes.31RHS. Canna Plant Care | RHS Advice
Cut the stems back before moving the pot, and let it drain well first. Bring the pot back outside after the last frost.
Pots left outside are riskier than beds, because the soil in a container freezes from all sides and gets colder than the ground does. If you have no room for pots, tip the rhizomes out and store them in boxes, as for plants lifted from a bed.
Waking and Dividing Cannas in Spring
Bring stored rhizomes out in spring and divide them before potting or planting.32Longfield Gardens. How to Split Canna Bulbs: A Guide for More Summer Color The eyes, the growth buds that make new stems, often swell or turn pink then and are easy to spot.33Longfield Gardens. How to Split Canna Bulbs: A Guide for More Summer Color
Snap rhizomes apart at natural branch points, or cut with a clean knife.34Longfield Gardens. How to Wake Up Canna Bulbs for a Vibrant Spring Garden Each piece needs at least one or two healthy eyes, since a piece without one won’t grow.35Longfield Gardens. How to Wake Up Canna Bulbs for a Vibrant Spring Garden Keep pieces about the size of a large potato, because bigger pieces hold more energy and grow faster.36Longfield Gardens. How to Wake Up Canna Bulbs for a Vibrant Spring Garden Let cut surfaces dry a day before planting.
Plant firm, plump pieces with visible eyes and skip soft, hollow or dried-out ones. A piece with a good eye but a damaged end can be trimmed back to healthy tissue.
For earlier flowers, pot up indoors a few weeks before the last frost, and plant out once the soil has warmed. Water lightly until shoots appear.