Calla lily, also known as arum lily, is not a true lily. It belongs to the genus Zantedeschia which originates from South Africa. The huge, flower-like spathes of the calla lily are now coming in a lot of different colors, making it a more popular house plant as well as a garden and patio plant.
Calla lillies flower from early to late summer on sturdy upright stems. They look nice because they have pretty leaves. The broad, bright green leaves are often speckled with white or silver. You can store the rhizomes, or fleshy roots, of most calla lilies over the winter and plant them again in the spring. The exception is white arum lily (Zantedeschia aethiopica) which is hardy outside in mild areas.
Watch out for confusion with the hardy pond plant bog arum (Calla palustris). Calla palustris needs to be grown in shallow water at the edge of a pond, even though the name and white flowers may sound alike.
Calla lilies are gorgeous flowers that can really brighten up any garden. Their large, creamy white blooms add elegance and sophistication. While calla lilies are relatively low maintenance, they do require dividing every few years to keep the plants healthy and blooming vigorously. So when is the best time to separate calla lily bulbs?
Why Should You Divide Calla Lily Plants?
Dividing calla lily plants serves several purposes
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Prevents overcrowding. If calla lily clumps become too dense, there won’t be enough space for new shoots and blooms to form. The plants will produce fewer and smaller flowers each year.
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Rejuvenates the plants. Dividing stimulates new root and shoot growth. This results in more blooms and healthier plants overall.
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Multiplies your plants, Dividing the rhizomes allows you to create more calla lily plants for your garden It’s an easy and cost-effective way to expand your collection,
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Improves blooming. Without division, blooms tend to diminish and possibly stop altogether after a few years. Dividing encourages abundant flowering.
So for the healthiest, most productive calla lily plants, periodic division is essential. But timing is critical.
When to Separate Calla Lily Bulbs
Calla lilies have rhizomatous roots that spread horizontally underground. It’s these rhizomes that you divide. The best time to divide calla lilies is either:
- In late winter or early spring after all danger of frost has passed.
- In late summer or fall when the plants have finished blooming for the year.
Dividing in late winter or early spring allows the new divisions time to establish before the summer growing season. But late summer or fall division can work well too.
Here are some tips for dividing at both times of year:
Spring Division
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Wait until the threat of hard frost has passed. Dividing too early could damage new shoots emerging from the rhizomes.
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Dig up the entire plant and gently wash off excess soil to expose the rhizome mass. Trim any rotted or damaged portions.
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Use a sharp, sterilized knife or garden shears to slice the rhizome mass into pieces, ensuring each division has 3-5 shoots and plenty of healthy roots.
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Replant divisions right away into prepared garden beds enriched with compost. Space 12-24 inches apart.
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Keep the plants well-watered as they establish. New growth will emerge within a few weeks.
Fall Division
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Dig up calla lily clumps after the foliage has yellowed or been killed by frost.
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As in spring, wash and trim the rhizomes then divide them into smaller pieces, keeping several shoots per division.
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Pot up the divisions in a sterile potting mix. Water them in well.
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Overwinter the potted divisions in a cool, frost-free location. A garage, basement, or cold frame works well.
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In spring after the danger of frost has passed, transplant the divisions back into the garden.
How Often to Divide Calla Lilies
Most calla lily varieties should be divided every 2-3 years for optimal growth and flowering. Signs it’s time to divide include:
- Declining flower production and smaller blooms.
- Centers of plants dying out.
- Overcrowded clumps with poor air circulation.
- Offsets forming more than 6 inches away from parent plants.
Zantedeschia aethiopica, the common white calla lily, may only need division every 4-5 years. While yellow calla lilies (Zantedeschia elliottiana) appreciate more frequent division every 1-2 years as they spread rapidly.
Monitor your plants and divide when congestion and diminished blooming occurs. Dividing too frequently can stress calla lilies, so allow them a couple years recovery between divisions.
How to Divide Calla Lily Plants
Here’s a simple step-by-step guide to safely dividing your calla lilies:
Gather Supplies
- Sharp knife or garden shears
- Hand trowel or garden fork
- Container of water to hold divisions
- Sterilized potting mix (for fall division)
- Compost or bulb fertilizer (for spring replanting)
Select Mature, Established Plants
Focus on dividing calla lilies that are at least 2-3 years old and showing signs they need division.
Dig Up the Roots
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Water plants thoroughly 1-2 days before dividing. This makes digging easier.
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Carefully dig up the entire calla lily clump using a garden fork. Try to keep the root mass intact.
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Gently shake or hose off excess soil so rhizomes are clearly visible. Remove old foliage and any bug-damaged, slimy, or rotten corms/roots.
Divide the Rhizomes
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With a sterilized knife, slice the rhizome mass into smaller pieces. Each should have 3-5 healthy shoots and plenty of robust roots.
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Divisions that are too small won’t thrive. Discard any that lack sufficient shoots or roots.
Replant the Divisions
For spring:
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Enrich garden soil with compost or bulb fertilizer.
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Plant divisions 12-24 inches apart, at the same depth as originally grown.
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Water well and add mulch to retain moisture while plants recover.
For fall:
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Pot up divisions individually in sterilized potting mix amended with compost.
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Overwinter potted plants in a cool 40-50°F location safe from hard freezes.
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In spring, transplant into prepared garden beds after frost danger has passed.
Provide Post-Division Care
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Keep divisions well-watered so new roots and shoots establish quickly.
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Stake taller varieties if needed until plants take hold.
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Resume normal fertilizing and mulching once growth takes off.
Follow proper timing and techniques, and your divided calla lily plants will flourish. Just be sure to allow them a few years before dividing again. With proper ongoing care, calla lilies separated at the right time will thrive and enhance your garden with their spectacular blooms for years to come.
How to plant calla lily (Zantedeschia)
Calla lily grows from thick rhizomes or fleshy roots that are sold when dormant in winter or spring. Ready-grown plants can be bought in spring and summer, often when in full flower.
Buy in the winter or spring and plant 8–10 cm deep in a good, peat-free multipurpose potting compost to grow from rhizomes that are dormant. Either pot up and start into growth indoors for earlier flowers, or plant outside after the frosts. Plants that were grown indoors need to be “hardened off” or acclimatized to the outdoors by being left out for longer and longer periods of time.
If you want to grow calla lilies in the ground, make the soil better by adding a lot of well-rotted compost or a special soil conditioner. Space plants 30-45 cm apart.
How to care for calla lily (Zantedeschia)
Regular watering is important to maintain the handsome lush growth of calla lilies. Ideally, keep compost moist but take care not to over-water either. Once the calla lily shoots start to flower, feed them every three to four weeks with a liquid fertilizer that is high in potash, like tomato fertilizer. Regularly remove dead and faded flower stems and leaves.
Once the flowers are gone, feed and water the calla lily every few weeks, but be careful not to give it too much water, until the leaves start to fall off. Bring potted plants indoors before the frosts and leave in the pot whilst dormant. If you want to keep your calla lilies alive all winter, dig them up and put the rhizomes in trays of just-moist compost. Make sure they are kept somewhere cool and out of the frost. Moving the roots to a new pot with wet compost in late winter and setting it somewhere warm will help it grow.
Dividing Calla Lilies
How do you divide calla lily bulbs?
Dividing calla lily bulbs is a simple process that can help propagate and rejuvenate your plants. Here’s a step-by-step guide on how to do it: Timing: The best time to divide calla lily bulbs is during their dormant period, which is typically in late winter or early spring.
Should you divide calla lilies?
Increase in Quantity: Dividing calla lily bulbs allows you to multiply your plant collection. Each division can be replanted separately, resulting in more calla lilies in your garden or for sharing with others. Space Management: If your calla lilies have outgrown their designated area, dividing the bulbs helps manage space.
When is the best time to divide calla lily bulbs?
Timing: The best time to divide calla lily bulbs is during their dormant period, which is typically in late winter or early spring. Preparation: Start by preparing the necessary materials, including gardening gloves, a spade or garden fork, a clean and sharp knife or garden shears, and potting soil or compost.
What happens if you divide calla lily bulbs?
There are a few potential problems that can arise when dividing calla lily bulbs: Damage to the bulbs: Dividing calla lily bulbs involves physically separating them into smaller sections. If not done carefully, there is a risk of damaging the bulbs, which can affect their ability to grow and thrive.