When to divide cannas?

Dividing Cannas

SERIES 18 | Episode 23

The canna must be one of the most under-used plants in Australia. They’re as tough as old boots, need little maintenance and produce a kaleidoscope of colour.

The modern-day cannas emanated from the Canna musifolia. “Musifolia” simply means it’s got leaves like a banana leaf. From these plants hybridisers have bred new ones. Each flower produces seed heads and seeds. When the Spanish and Portuguese found the seeds in Central America, they used them to make rosary beads and because they looked like shot, they used to call them Indian shot.

It’s difficult to produce cannas from seed. The simplest way to propagate them is by division. Just dig the canna up, shake the dirt off and divide the rhizomes. They usually break apart fairly easily. Look for good strong shoots because they’re the ones that will produce the new luxuriant growth.

Just before planting prepare the ground. They like a nice, sweet soil, so sprinkle some dolomite and scratch it in, then add blood and bone. And be sure to add some sulphate of potash because they need potash. Cannas love a good, rich soil and one with plenty of potash.

A canna bought from a retail nursery will come with all the leaves taken off and just the stems. Plant these in the hole and spread the roots evenly. You don’t want to bunch the roots up. The soil needs to be just covering the crown and that’s all – bury them too deeply and they will rot – and add some water.

The first flowers on a newly-planted canna, given the right conditions, should appear within about six to eight weeks. Every spike produces two lots of flowers, so that gives them a long flowering season. Remember that clumps of canna will grow quite big if left in one spot for too long. Lift them up every second year, and divide them for more cannas to play with.

I particularly like mass plantings of cannas in drifts, so you get large swathes of colour. So get some rhizomes and plant them in your garden for a wonderful effect.

How to Transplant a Canna Lily

Canna lilies have been a garden favorite since the 16th Century, with their large showy flowers and furled leaves resembling those on a banana tree. These perennials are a beautiful addition to any garden, adding a majestic touch with their bold presence and bright colors. Canna lilies can grow up to one meter in height and come in a range of colors that include red, golden, pink, orange and yellow.

Keep these steps in mind when transplanting hardy canna lilies to your garden to add a splash of color to a particular spot.

Step 1 – Select Appropriate Site

Select a location that receives at least six hours of direct sunlight, although off-white flowering canna lilies prefer partial shade in order to thrive and produce healthy flowers. All lilies prefer a moist well-drained soil with plenty of organic matter.

It is always best to transplant the lily just after sunset to minimize the exposure of the delicate roots to the bright sunlight in order to prevent the lily from going into shock.

Step 2 – Prepare Site for Planting

Spread a layer of compost over the site a day before transplanting the lily and rake it in to ensure it goes deep into the soil. Also water the soil well.

On the transplanting day, dig a hole at least 6 inches deep in the soil with a shovel or spade. Make sure the hole is roughly a few inches wider than the root ball.

Step 3 – Remove Lily from Pot

Carefully lift the lily from the pot you purchased it in, ensuring any clumps of dirt sticking to its roots remain. If it is hard to remove the lily from the pot, simply roll it on the ground gently for one rotation to loosen it. Make sure the roots do not circle the bottom of the root ball, and loosen them if they do to encourage them to spread in the soil.

Step 4 – Transplant Lily in the Soil

Position the lily into the hole carefully, with the top of the potting soil ball in line with the surrounding soil surface. You may add or remove soil underneath the canna lily to adjust the height, but lift the canna lily by the shoot carefully when doing so. Place the lily in the center of the hole and gently spread its roots to encourage them to spread and grow.

Backfill the hole with soil so the lily is secure and press it down with your fingers to remove any air bubbles or gaps.

Step 5 – Caring for the Canna Lily

Water the canna lily well, especially after transplanting. Let the water collect around the plant and then sink into the soil.

Water it once daily to evenly moisten the soil, or more during hot, dry weather. Heavy watering after prolonged periods will cause the leaves to tear.

Add a layer of mulch over the site to retain moisture and prevent competing weeds from growing.

Use a slow-release fertilizer once in the growing season and water the plant well before and after the application.

Canna lily (Katie Woods photo)

Canna lilies are tropical-looking perennials.

Canna lilies come in a variety of colors, including red, orange, yellow pink, and cream, as well as some striped and spotted colors. Regular varieties range in height from 3 to 5 feet, while dwarf varieties grow to about 2 feet tall.

Iowa State University Extension offers a list of canna lily varieties and descriptions of each.

Related: How to plant bulbs this fall

In the winter

You can start canna lilies indoors in pots, planted four inches deep, before the last frost.

In the spring

Transplant canna lilies that were started indoors over winter, or plant canna lilies in the ground or in large containers. Plant rhizomes several inches deep and about two feet apart, according to Clemson University Extension. Make sure you plant the rhizome with the eyes facing up.

Canna lilies should be planted in full sun, but they can tolerate partial shade if necessary. Canna lilies grow best in moist, richly organic soil that drains well.

Iowa State University Extension recommends 10-10-10 fertilizer in the spring.

In the summer

During the summer months, water flowers thoroughly. Fertilize again in mid-summer.

Watch for symptoms of viruses, like canna yellow mottle virus and bean yellow mosaic virus: streaking or mottling of foliage, stunting or poor flowering. Iowa State University Extension explains that canna lilies cannot be cured of these viruses.

Canna lily (Katie Woods photo)

In the fall

After fall frost has blackened the foliage, canna lily rhizomes must be dug up and stored indoors until spring, unless planted in USDA hardiness zones 7 to 10.

Dig around the plant’s stem, about a foot out. Lift the clump out of the ground by the stem, wash the roots off with water and cut off the tops of the plant, leaving just a few inches of stem.

Place rhizomes in brown paper grocery bags and store in an attic, basement or crawlspace where the temperature will remain between 45 and 60 degrees F until spring, according to Penn State University Extension.

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Q: With the onset of fall, it will soon be time to dig up our canna tubers. Should we separate the tubers now or wait until we are ready to plant them next spring? Last spring, my wife Linda did not separate them. They grew just fine. However, now they have many stalks on them. If we do separate them, what is the correct method?

—Bill and Linda Boyle

A: Canna tubers very seldom will survive our winters. So each fall, after the greens have been blackened by frost, gardeners can dig up the tubers for storage over the winter. Linda and Bill are only asking about dividing the tubers, but it is a good time to review the entire process of saving and dividing canna tubers for next spring.

After the first killing frost, the greens of cannas and other tender bulbs will blacken and it is time to dig them up:

•Cut back the tops of the cannas to three to four inches. Loosen the soil around the cluster of tubers. A garden fork, a sunny day and dry soil make the job fairly easy.

•Turn the clumps over and allow the tubers to dry for several hours or longer, up to a week, but be sure to move to a covered area if rain is in the forecast.

•Carefully dust off the loose soil.

•Dust the tubers with fungicide if you have problems with rotting during storage, if your storage area is not ideal, or just to protect from fungus during the winter.

•Store in a box of peat moss, vermiculite or sand. Keep the container open or punch holes in it to allow air circulation. Others recommend storing on shelves, racks, or mesh bags to allow air circulation.

•Store the containers in a cool (temperatures below 50 degrees) but frost-free area, dark and dry.

•Check monthly during storage. Discard any rotting tubers. If they shrivel or dry, rehydrate the tubers in water for a few hours, allow them to dry for a day or so, and then replace in storage.

When dividing canna tubers, there are differing camps. Some prefer dividing the tubers in fall, others in spring. I prefer spring. Also note that you do not have to divide the tubers. However, they generally reproduce quite rapidly and become an unwieldy mass. Dividing at least every two or three seasons is a good idea.

•Locate the eyes on each tuber. Eyes are the buds, like the eyes on a potato.

•Divide the tuber into sections so that each section has at least three eyes. One eye may work but I prefer to err on the side of caution, thus include multiple buds on each piece.

•Fungus can be a problem on the cut ends of the tuber. I suggest applying a dusting of fungicide to the cut ends. In a pinch, use rooting hormone, it generally contains fungicide.

•Share or trade the extra rhizomes with other gardeners.

•Canna lilies like full sun, rich soil and plenty of water. For an earlier bloom, the tubers can be potted up indoors in the early spring. Plant out after all chances of frost have past.

Hardy hibiscus problems revisited

Q: I read with interest your column today on hardy hibiscus. I had sent you a question about them in the early summer, which you graciously answered.

I had the same problem (on my hardy hibiscus)—lacy leaves and veins with something eating all the leaf material for two years in a row. I used spinosad in the form of Captain Jack’s Deadbug spray (available at Neighbors in Hellertown and completely organic) starting in early June after the plant had been eaten to shreds, figuring I had nothing to lose. Per instructions, I sprayed the plant to run-off every time I saw a sawfly, sometimes two or three times a week. It took most of June and some of July, but the plant has rebounded — not as tall as usual, but robust with flowers and buds. Next summer, I’ll know to get started spraying it just as soon as I see even one sawfly.

Added benefit: I saw that spinosad could be used on Brussels sprouts. I’ve always had a problem with bugs eating the leaves although I still got sprouts. So I applied the spinosad to the Brussels sprouts also, following directions of spraying to run-off but applying no more often than once every week for no more than six times. My Brussels sprouts are huge and un-bugged. That’s one terrific organic product. I heartily recommend it. P.S. It is no help for squash beetles.

—Andrea Wittchen

Sue Kittek is a freelance garden columnist, writer, and lecturer. Send questions to Garden Keeper at [email protected] or mail: Garden Keeper, The Morning Call, P.O. Box 1260, Allentown, PA 18105.

This Week in the Garden

•Plant:

•Garlic and shallots; spring flowering bulbs.

•Plant out perennials, shrubs and trees. Water regularly as necessary until the ground freezes.

•Plant pansies, asters, mums, kale, cabbage, ornamental peppers and other fall ornamental plants.

•Sow seeds that need a cold period for germination, poppies, for example.

•Seasonal:

•Prepare beds for bulbs to be planted in a few weeks.

•Order garlic, asparagus and rhubarb for fall planting.

•Order bulbs, flower and fruit plants, and shrubs for fall planting. Shop nurseries for end-of-season bargains or new fall arrivals.

•Allow final flush of flowers to go to seed. They provide food for birds and small mammals during the leaner fall and winter months.

•Weed regularly and cut off flowers of any weeds you don’t get to.

•Apply preemergent herbicides to garden beds at recommended intervals, 4 to 6 weeks for annual weed control.

•Lawns:

Finish this week: Overseed, seed and sod lawns. Fertilize lawns and treat for broadleaf weeds. Complete aeration and dethatching projects.

•Sod as weather cools, September-October; fall fertilize if desired from now until mid-October

•Treat for grubs, chinch bugs and sod webworms.

•Apply broadleaf weed control, through mid-October

•Cut lawns only when needed; use fresh gas and a sharp blade.

•Water newly seeded areas in weeks that have less than an inch of rainfall.

•Chores:

•Cut to the ground: Allium moly, spent hollyhocks.

•Trim bleeding hearts, blanket flowers, hardy cranesbills, and Shasta daisies, allowing the basal foliage (the bottom clump of leaves) to remain.

•Remove flower stalks or scapes from: daylilies, gayfeather (liatris), and yuccas.

•Watch for frosts and protect tender plants. Cover with frost covers—even old sheets on evenings with frost warnings. It will extend the season a few weeks.

•Allow attractive seed heads to remain when clearing the garden. They provide food for birds as well as winter interest.

•Allow bulbs, like amaryllis, to die back and go dormant for a month or two so they are ready for winter blooming.

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