Photo: Wouter Hagens / Public domain

Water Hyacinth Care

Pontederia crassipes · Pontederiaceae

⚠️ Toxic to pets 🎯 Easy ☀️ Full sun 💧 Every 7 days

🕮 6 min read 🕓 Last reviewed: 2026-08-23

Care at a glance

Light

Full sun

Temperature

12–32 °C (54–90 °F)

Soil

grows in water with pebbles, or a well-draining mix

Difficulty

Easy

Mature size

15–50 cm (6–20 in)

Pet safety

Toxic to pets

Care effort Medium

The short version

Beginner-friendly and forgiving.
Give it Full sun.
Water every 7–7 days.
Keep away from cats and dogs.

The Water Hyacinth (Pontederia crassipes) is an aquatic plant grown submerged in freshwater aquariums. It comes from South America and is rated Easy to keep, reaching 15–50 cm. Here is how to grow it underwater — lighting, substrate, CO₂, placement and propagation.

Also known asPontederia crassipesホテイアオイ水葫芦Jacinto de aguaJacinthe d'eau

📋Quick facts

Growth rate	Fast
Mature size	15–50 cm (6–20 in)
Native region	South America
Plant family	Pontederiaceae
Toxicity	Mildly toxic
Air-purifying	No
Ideal for	beginners, a pop of colour

⚖️Pros & cons

Pros

Hard to kill; great for beginners
Fast, rewarding growth
Flowers indoors

Cons

Toxic to cats and dogs
Needs high humidity to look its best
Needs a bright, sunny spot

🐟Growing it in an aquarium

Keep the water at 12–32 °C. Stable, gently moving water and regular partial water changes keep it healthy; sudden swings in temperature or chemistry cause melting.

Light

Give it Full sun-equivalent aquarium lighting. Low-tech tanks suit undemanding species; brighter light (and often CO₂) brings out the best colour and compact growth but also feeds algae, so balance it carefully.

Soil

Plant it in grows in water with pebbles, or a well-draining mix. Rooted species are hungry feeders — use root tabs or a liquid aquarium fertiliser (and CO₂ for demanding types). Epiphytes like Anubias, Java fern and Bucephalandra must NOT be buried: tie or glue their rhizome to wood or rock, or they rot.

Its size and habit suit a spot in the foreground, midground or background depending on how tall it grows; trim and replant tops to keep it dense.

✂️How to propagate, step by step

Spring and early summer, during active growth, give the best success. Here is how to do it, step by step:

offsets (pups)

Wait until the offset (pup) is about a third the size of the parent.
Unpot the plant so you can see where the pup joins it.
Separate the pup, keeping as many of its own roots as you can.
Let any succulent cuts callus for a day; pot rooted pups straight away.
Plant in suitable mix and water lightly until it establishes.

seed

Sow fresh seed onto the surface of moist, fine seed-starting mix.
Cover lightly only if the seed needs darkness; most need warmth of 20–25 °C.
Keep humid under a clear cover in bright, indirect light.
Germination ranges from days to months depending on the species — be patient.
Prick seedlings out into their own small pots once they have a few true leaves.

🔬Classification

Plant type	Aquatic plant
Genus	Pontederia
Family	Pontederiaceae · Pontederiaceae
Native to	South America

🩺Common problems

Symptom	Likely cause	What to do
Yellowing leaves	Usually overwatering or poor drainage	Let the soil dry more between waterings and make sure the pot drains.
Pests (mites, mealybugs)	Dry conditions or a new infected plant	Wipe the leaves, rinse, and treat with insecticidal soap or neem.
Algae on leaves or glass	Too much light or excess nutrients in the water	Cut the lighting period, reduce feeding, and add algae-eating clean-up crew.

🩺 Plant Doctor →

🐛Pests & prevention

The usual indoor pests are spider mites (fine webbing, speckled leaves), mealybugs (white cotton-wool tufts), scale (small brown bumps), and fungus gnats (tiny flies from soggy soil). Inspect any new plant before it joins the others, wipe the leaves now and then, and let the topsoil dry to keep gnats away. At the first sign, isolate the plant, wipe or rinse off what you can, and treat with insecticidal soap or neem oil every week until it is clear.

🐾Is it safe for pets?

The Water Hyacinth is toxic to cats and dogs (calcium oxalate crystals; accumulates irritant compounds). Keep it out of reach of pets and children. If you think an animal has chewed it, contact your vet or a pet poison line. If a curious cat or dog chews it, the insoluble calcium oxalates act like tiny needles, causing intense burning of the mouth, drooling, pawing at the mouth, and sometimes swelling that makes swallowing hard. It is rarely life-threatening in small amounts, but rinse the animal’s mouth, take away any plant pieces, and call your vet if symptoms are severe or last more than a short while.

Toxicity information is a general guide based on ASPCA data. If your pet or child may have eaten any part of a plant, contact a vet or poison control right away.