Giant Arrowhead (Aztec Arrowhead) care

Light

Aim for at least 4-6 hours of direct sun on the leaves. Requires full sun for best growth and flowering; minimum 6 hours of direct sun daily — plants in shade become etiolated and rarely flower. If your only bright window faces south, that's perfect for giant arrowhead — same window any aroid would fry on.

Watering

Watering giant arrowhead: permanently aquatic — plant in still or slow-moving water 10–15 cm (4–6 in) deep; tolerates up to 30 cm (12 in).. The number that matters isn't the day of the week — it's how dry the top 2-3 cm of the pot feels. A finger in the soil tells you more than a watering app. After every watering, tip the saucer. Grow in a large, submerged planting container (minimum 10-litre/2-gallon) weighted with gravel to prevent tipping; the large leaves catch wind and can topple unsecured containers.

Soil and pot

Giant Arrowhead grows best in heavy loam or enriched aquatic compost. Use a dense loam-based mix rather than peat compost to anchor the large root system; top-dress with pea gravel to prevent soil dispersal into the pond water. 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 Arrowhead sits happiest at around High (pond surface environment) humidity and 15–35 °C (active growth); plants die back below 10 °C; in frost-prone areas treat as an annual or overwinter containers indoors (59–95 °F (active growth); dies back below 50 °F; overwinter indoors in frost-prone climates). No supplemental humidity required in outdoor cultivation; the emergent habit places foliage in ambient outdoor humidity which is adequate. If you keep the room above 15–35 °C (active growth); plants die back below 10 °C; in frost 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 arrowhead sparingly. Push 2–3 aquatic fertiliser tablets into the compost at the start of the growing season; reapply every 6–8 weeks through summer to maintain the high nutrient demand of this large, fast-growing species. 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 arrowhead in the Growli community. Each is annotated with the most common cause so you know where to start.

• Wind rock and container tipping — The large leaf canopy acts as a sail in wind; use a heavy container (minimum 10 litres) filled with dense clay loam, and place in a sheltered pond position or weigh the container base with additional stones.
• Invasive spread by seed — Sets large quantities of seed that can germinate prolifically in warm climates; deadhead spent flower stalks before seed dispersal to prevent unwanted spread, especially near natural waterways.

Propagation

Divide established clumps in spring by separating rooted offsets or tubers; pot individually into aquatic baskets and return to the pond. Can be grown from seed — sow on the surface of waterlogged aquatic compost at 20–25 °C (68–77 °F) and do not allow to dry out. 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 Arrowhead is pet-safe. Sagittaria species are not listed on the ASPCA toxic plant database and are widely considered non-toxic to cats and dogs. The aquatic arrowheads (Sagittaria spp.) should not be confused with arrowhead vine (Syngonium podophyllum), which is toxic and a completely different plant family. 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 Arrowhead deep-dive guides

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

• Common giant arrowhead problems & fixes
• Giant Arrowhead watering schedule
• Giant Arrowhead light requirements
• Best soil mix for giant arrowhead
• Giant Arrowhead fertilizing guide
• When to repot giant arrowhead
• How to propagate giant arrowhead
• How to prune giant arrowhead
• What's eating my giant arrowhead?
• Giant Arrowhead growth rate & size
• Giant Arrowhead cold hardiness
• Giant Arrowhead temperature & humidity
• Is giant arrowhead toxic to cats & dogs?
• Is giant arrowhead toxic to cats?
• Is giant arrowhead toxic to dogs?
• All 9 Sagittaria varieties
• Getting giant arrowhead to bloom

Featured in these plant shortlists

Giant Arrowhead qualifies for 7 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

• Best pet-safe houseplants — Houseplants the ASPCA lists as non-toxic to cats and dogs — every one verified against the ASPCA toxic and non-toxic plant list.
• Best flowering houseplants — Indoor plants grown for their blooms — selected from the flowering species in Growli’s plant-care library.
• Best pet-safe flowering plants — Flowering houseplants the ASPCA lists as non-toxic to cats and dogs — colour and blooms in a pet home, without the worry.
• Best pet-safe plants for bright light — Non-toxic to cats and dogs and happy in a bright, sunny spot — safe plants for your best-lit windowsill.
• Best houseplants for full sun — Houseplants that want direct sun — the species for a hot south or west-facing windowsill where shade-lovers scorch.
• Best cat-safe plants — Houseplants the ASPCA lists as non-toxic to cats (and dogs) — safe greenery for a home with a curious cat.
• Best dog-safe plants — Houseplants the ASPCA lists as non-toxic to dogs (and cats) — safe greenery for a home with a curious dog.
• Browse all 29 plant shortlists — pet-safe, low-light, drought-tolerant and more

Related guides

Giant Arrowhead is also known as Giant Arrowhead, Aztec Arrowhead, California Arrowhead, and Giant Duck Potato.

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