Can Arum Lily Grow in Water? Setup, Care and Troubleshooting

Yes, arum lilies can grow in water, but there are important conditions that determine whether they thrive or rot. Zantedeschia aethiopica (the classic white arum/calla lily) is actually classified as a marginal aquatic plant and can tolerate water up to 30cm (about 12 inches) deep over its roots. The other common type, Arum italicum (Italian arum), is a different beast entirely and really belongs in moist woodland soil rather than standing water. Get the species right, keep the crown (the growing tip at the top of the rhizome) above or just at the waterline, ensure good oxygen in the water, and you've got a setup that genuinely works long-term.

Which 'arum lily' do you actually have?

This is the most important question before you do anything else, because 'arum lily' is one of those common names that gets glued to several totally different plants. Most gardeners searching this topic have one of two things:

• Zantedeschia aethiopica (white arum lily / calla lily): The big, classic white funnel-flowered plant. This one is native to marshy, seasonally flooded habitats in southern Africa, which is exactly why it handles wet and even pond-margin conditions so well. This is the one you CAN successfully grow in water.
• Arum italicum (Italian arum / Lords-and-Ladies): A woodland perennial with arrow-shaped leaves and red berries in autumn. It goes dormant in summer and re-emerges in autumn/winter. This plant prefers moist, humus-rich soil and is NOT suited to standing water or hydroponic setups.
• Zantedeschia hybrid cultivars (colored callas: pink, yellow, purple): These are derived from different species than Z. aethiopica and are generally less water-tolerant. They prefer moist but well-draining conditions. Proceed with water culture more cautiously with these.

If you have the white arum lily (Z. aethiopica), you're in luck. The rest of this article is primarily written for that plant and its close cousins, since that's where water culture actually makes sense. If you've got Italian arum, keep it in moist garden soil and save yourself the frustration of watching it decline in a water container.

Your three main water-growing options

When people say 'grow in water,' they usually mean one of three things, and each has a different success rate with arum lilies.

Option 1: Roots submerged, crown at or just above the waterline (best choice)

This is the sweet spot for Z. aethiopica and the method recommended by the RHS and commercial aquatic plant suppliers. You sit the rhizome in a shallow container so the roots and base are in water, but the growing crown (the top of the rhizome where shoots emerge) is just at or barely above the water surface. Aim for roughly 8 to 15cm (3 to 6 inches) of water over the crown at most, with the crown itself ideally sitting at the waterline rather than being deeply buried under water. This mimics the plant's natural pond-margin habitat and prevents the stagnant, anaerobic conditions around the crown that cause rot.

Option 2: Pond or water feature marginal planting

This is Z. aethiopica's natural happy place. Planted in a basket or directly in the margins of a garden pond, standing in water up to 30cm (12 inches) deep, these plants can stay in place for years. Thompson and Morgan and the RHS both confirm this depth tolerance. The water itself provides cooling, the roots stay consistently moist, and the plant comes back season after season. If you have a garden pond or patio water tub, this is the most reliable long-term method.

Option 3: Semi-hydroponic or hydroponic-style growing (advanced, indoor)

This involves growing the plant in an inert medium (like clay pebbles or perlite) with a nutrient solution instead of soil. Research, including work from semihydroponic and ebb-and-flow growing systems, confirms calla lilies can be grown this way when nutrient and oxygen levels are managed carefully. It's more demanding to maintain than a simple water container, but it works well indoors where you can control conditions. The key variables are pH (aim for the root zone to sit around 6.0 to 6.5), electrical conductivity (EC) of the nutrient solution (starting from clean water around 0 to 0.6 mS/cm and building up with diluted fertilizer), and dissolved oxygen above 6 mg/L using aeration.

Light, temperature, and seasonal timing

Getting these three things right matters just as much as the water setup itself. I've seen people do everything right with the container and water and still end up with a failing, yellowing plant because the conditions around the water setup were wrong.

• Light: Arum lilies need a warm, bright spot. Indoors, place them in the brightest window you have, ideally getting 4 to 6 hours of direct or very bright indirect light daily. Outdoors, a spot with morning sun and afternoon shade works well in hot climates; full sun is fine in cooler regions.
• Temperature: The happy range for active growth is roughly 15 to 25°C (60 to 77°F). Below 5°C (41°F) will kill tender rhizomes, so outdoor water setups need to come indoors before the first frost in cold climates. Water in containers cools fast, which is a bigger risk than soil.
• Dormancy: Zantedeschia rhizomes have a natural dormancy period, typically about 10 to 12 weeks after being lifted or after the growing season ends. Trying to force growth in water during this window will fail, and keeping wet rhizomes in dormancy leads to rot. If your plant seems stuck and won't sprout, check whether it's in a dormancy phase first.
• Seasonal setup outdoors: Start outdoor water container planting in spring after frost risk has passed. In mild climates (USDA zones 8 to 10), Z. aethiopica can overwinter in a pond margin outdoors. In colder zones, lift the rhizome in autumn, let it dry briefly, and store it cool and dry until spring.

Getting the container, water quality, and feeding right

Container choice

For marginal pond planting, use a purpose-made aquatic basket or a wide, shallow container that holds enough soil or gravel to anchor the rhizome while sitting in the water. For indoor semi-hydro setups, any opaque container works (opaque prevents algae growth from light reaching the water). A container that holds 2 to 4 liters per plant gives roots room to expand. Avoid clear glass for long-term setups unless you're prepared to clean algae frequently.

Water quality and changes

Tap water is usually fine, but if your water is high in alkalinity, it can cause nutrient imbalances over time, which shows up as yellowing or poor growth. Change or refresh the water every 1 to 2 weeks in warmer months when the plant is actively growing and evaporation is higher. In a pond, natural water circulation handles this. In a static indoor container, partial water changes (replacing about half the volume) help flush out salt buildup and keep nutrient levels stable.

Oxygenation

Stagnant, oxygen-depleted water is the number one cause of root rot in water-grown arum lilies. In a pond, oxygenation comes naturally from surface agitation and aquatic plants. In a static container, you have a few options: a small aquarium air pump with an air stone is the simplest solution, moving the water slightly to maintain dissolved oxygen above 6 mg/L. Alternatively, do more frequent water changes and keep containers in a spot with some air movement. Avoid sealed, still containers with no aeration in warm weather.

Fertilizing in water

In a soil setup, the plant has buffering from the growing medium, but in water culture there's no buffer, so you need to feed regularly but carefully. For a simple water container, use a diluted balanced liquid fertilizer every one to two weeks during active growth. Once buds form, switch to a potassium-rich feed (a diluted tomato fertilizer works well) applied weekly until flowering is over. For hydroponic setups, aim for a roughly equal N:K ratio in the nutrient solution, and monitor EC and pH regularly. Nutrient deficiencies show up as specific leaf patterns (yellowing in distinct patterns depending on which element is missing), so if the leaves look off, that's your first diagnostic clue.

Starting, transplanting, and long-term care (indoor vs outdoor)

Starting from a dormant rhizome in water

The RHS recommends starting dormant rhizomes with the top of the rhizome just showing above the surface, watering sparingly until shoots appear (usually within a couple of weeks in a warm, bright spot). For water culture, I'd suggest starting the rhizome in barely moist, well-draining medium first until shoots are a few centimeters tall, then gradually introducing more water. Plunging a cold, dormant rhizome straight into a water container without any shoot growth is one of the fastest ways to end up with rot.

Transferring from soil to water

If you're moving an established, soil-grown plant to a water setup, rinse the roots thoroughly to remove all soil (trapped soil in water becomes anaerobic quickly and encourages rot bacteria). Let the rinsed roots air-dry for an hour, then place in your water container with the crown at or just above the waterline. Expect a brief adjustment period of one to two weeks where the plant looks slightly stressed before it settles in.

Indoor long-term water culture

Indoors, the main challenges are light and humidity. Keep the container in the brightest spot available, refresh water every one to two weeks, and feed lightly but consistently during the growing season. Watch for root crowding as the plant matures, as a root-bound plant in a small container will decline quickly. Repot (or move to a larger container) every one to two years.

Outdoor water features and patio tubs

In zones 8 and warmer, a patio water tub or pond margin is a low-maintenance long-term home for Z. aethiopica. Plant in spring, allow to establish through summer, and in colder zones bring the container inside before temperatures drop below 5°C (41°F). In zones 9 to 10, plants in a sheltered pond margin can stay outdoors year-round.

Soil vs water growing: an honest comparison

For most home gardeners, soil (or a pond basket with a layer of heavy loam) is the safer starting point. The advantage of water culture is mostly aesthetic (beautiful in a water feature or bowl) and practical in pond settings where the plant has room to grow naturally. If you're indoors and want the water-growing look, go semi-hydro with proper aeration rather than a simple static container.

When things go wrong: diagnosing and fixing the most common problems

Mushy rhizome or roots with a foul smell

This is bacterial soft rot (Erwinia), and it's the most common water-culture failure. The rhizome or stem base becomes mushy with a fishy, slimy smell. It usually starts when the crown is constantly submerged in stagnant, low-oxygen water or when a damaged rhizome is placed in water without drying first. Remove the plant immediately, cut away all affected tissue back to firm, healthy growth, dust cut surfaces with sulfur powder or let them air-dry for several hours, and start fresh in clean water with improved oxygenation and the crown positioned above the waterline. If the rot has reached the entire rhizome, the plant is not recoverable.

Yellow leaves

Yellowing has several different causes in water-grown arum lilies, so look at the pattern before acting. Uniform yellowing of older lower leaves is often normal aging, especially as the plant enters dormancy. Yellowing starting between leaf veins (interveinal chlorosis) usually indicates an iron or magnesium deficiency from pH being too high in the water (above 7.0). General pale yellow on new growth points to nitrogen deficiency. Adjust pH downward slightly and add a balanced diluted feed if deficiency is suspected. If yellowing is accompanied by a mushy smell, refer to the rot section above.

No new growth or sprouting

If a healthy-looking rhizome just sits in water without sprouting, the most likely cause is dormancy (the plant simply isn't ready to grow yet), cold water or air temperature, or insufficient light. Zantedeschia rhizomes have a dormancy period of around 10 to 12 weeks. Move the container to a warmer, brighter spot (aim for at least 18°C / 64°F), and give it another two to three weeks. Don't mistake a dormant rhizome for a dead one just because it's not moving. You'll usually see shoots within a couple of weeks once conditions are right.

Crown rot at the stem base

Crown rot (caused by Rhizoctonia or similar fungi) shows up as dark, water-soaked, browning tissue right at the base of the stems where they meet the rhizome. Unlike bacterial soft rot, it often doesn't smell as strongly at first. It's triggered by continuously saturated conditions around the crown with poor airflow. The fix is to reposition so the crown is above the waterline, improve oxygenation, and remove affected tissue. Cottony mold over affected tissue is a warning sign to act fast.

Algae taking over the container

Green algae in the water container is annoying but not directly harmful to the plant. It's caused by light reaching nutrient-rich water. The fix is straightforward: use an opaque container, do more frequent partial water changes, and reduce direct sun hitting the water surface rather than the plant leaves. A small amount of algae in an outdoor pond setup is actually fine and normal.

Pests in water-grown containers

Aphids and spider mites can still colonize the leaves even in water-grown plants, as they attack the foliage rather than the roots. Fungus gnats are less of a problem in water than in soil, but mosquitoes can breed in standing water containers. A small air pump that keeps the water surface moving prevents mosquito breeding. For aphids, a strong spray of water on the leaves or neem oil applied to foliage handles most infestations. Check the undersides of leaves regularly, especially indoors.

If you're exploring water culture for other lily types, the approach and tolerance levels vary considerably. Unlike Z. aethiopica, most lily types such as tiger lilies, rain lilies, or boat lilies have very different relationships with water, ranging from needing excellent drainage to true aquatic conditions, so it's worth checking the specific requirements for whatever you're growing alongside your arum lily. Boat lilies may tolerate or even thrive with their roots in water, but you still need to match the plant's specific depth and oxygen needs boat lilies have very different relationships with water. Rain lilies have different water needs than arum lilies, so check their specific requirements before trying water culture. Tiger lilies can be grown in water, but they are not true arum lily water plants, so you need to check the variety and mimic a pond-margin approach rather than full submersion tiger lilies can grow in water.