Giant Water Lily (Blue Water Lily) care

Light

Most houseplants will scorch where giant water lily thrives. Give it the windowsill you'd otherwise leave empty because everything else burned there. Requires at least 6–8 hours of direct sunlight daily; under strong sun the enormous flower colour is most vivid. Partial shade will severely limit flowering and leaf size. A plant moved abruptly from low light to direct sun bleaches in 48 hours — always acclimatise over a week.

Watering

Aim for permanently submerged — maintain 40–80 cm of water over the crown for giant water lily, but treat that as a starting point rather than a rule. A south-facing summer windowsill will dry the pot twice as fast as a north-facing winter room. Lift the pot; if it feels noticeably lighter than it did wet, water it. Plant rhizomes in large, wide aquatic baskets in fertile loam and submerge so the growing point sits 40–80 cm below the surface. Warm water is essential; the plant actively grows only when water temperature is above 24°C (75°F).

Soil and pot

Giant Water Lily grows best in rich, heavy loam aquatic compost. Use a nutrient-rich, clay-heavy loam in a large aquatic planter; this species is a vigorous feeder and responds well to a fertile substrate. Top-dress with coarse gravel to prevent soil dispersal. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Giant Water Lily sits happiest at around Ambient outdoor humidity humidity and 10°C to 35°C (actively grows above 24°C) (50°F to 95°F (actively grows above 75°F)). As an outdoor pond plant in its native range, high ambient tropical humidity is the norm; in temperate climates grow in a heated glasshouse pond where humidity is naturally elevated. If you keep the room above 10°C to 35°C (actively grows above 24°C) year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed giant water lily sparingly. Insert aquatic fertiliser tablets into the basket substrate every 2–3 weeks during the growing season (when water temperature is above 24°C); this large-leafed tropical is a heavy feeder. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on giant water lily in the Growli community. Each is annotated with the most common cause so you know where to start.

• Dormancy in cool water — Below 24°C (75°F) the plant ceases active growth and may die back entirely. In temperate climates, lift the tuber before water temperatures drop in autumn, store in barely moist peat at 18–20°C, and replant in late spring.
• Water lily beetle (Galerucella nymphaeae) — Adults and larvae strip the upper surface of leaves leaving brown scars; remove affected pads and submerge remaining foliage temporarily to dislodge larvae into the water for fish to consume.

Propagation

Division of the fleshy rhizome in early spring before growth resumes; each division should have at least one growth bud. Can be grown from seed sown in shallow water at 28–30°C, though seedling-to-flowering takes two or more seasons. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Giant Water Lily is mildly toxic to pets. Nymphaea gigantea is not specifically listed by the ASPCA; however, some Nymphaea species contain alkaloids (nupharamine alkaloids) in rhizomes that may cause gastrointestinal upset if ingested in quantity. Classified as mildly-toxic as a precaution; not expected to cause serious harm in brief contact but keep pets from chewing rhizomes. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Giant Water Lily deep-dive guides

Every aspect of giant water lily care, each with its own calibrated guide:

• Common giant water lily problems & fixes
• Giant Water Lily watering schedule
• Giant Water Lily light requirements
• Best soil mix for giant water lily
• Giant Water Lily fertilizing guide
• When to repot giant water lily
• How to propagate giant water lily
• How to prune giant water lily
• What's eating my giant water lily?
• Giant Water Lily growth rate & size
• Giant Water Lily cold hardiness
• Giant Water Lily temperature & humidity
• Is giant water lily toxic to cats & dogs?
• Is giant water lily toxic to cats?
• Is giant water lily toxic to dogs?
• All 27 Nymphaea varieties

Featured in these plant shortlists

Giant Water Lily qualifies for 1 curated Growli shortlist — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

• Best houseplants for full sun — Houseplants that want direct sun — the species for a hot south or west-facing windowsill where shade-lovers scorch.
• Browse all 29 plant shortlists — pet-safe, low-light, drought-tolerant and more

Related guides

Giant Water Lily is also known as Giant Water Lily, Blue Water Lily, and Australian Water Lily.

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• All 10153 plant care guides in the Growli library