Spiny Water-starwort (Callitriche hamulata)

Spiny Water-starwort

Callitriche hamulata

Delicate floating aquatic foliage, a quiet accent to small water features. Aquatic herbaceous perennial; common name: Spiny Water-starwort.

Partial sun
N/A/week
Beginner
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Plant Needs

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Sunlight Bright indirect sunlight; tolerates partial shade, avoid prolonged direct sun that can overheat shallow water
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Watering Maintain consistent clean, still or slow-moving shallow water (5–15 cm depth)
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Temperature Thrives in cool to temperate water; avoid extreme heat above 28°C which can cause foliage dieback
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Characteristics

  • Leaf: Submerged leaves are linear, 5–15 mm long; floating leaves are oval, 1–3 mm wide, with pointed tips
  • Flower: Tiny, inconspicuous greenish flowers without petals, borne in leaf axils
  • Stem: Slender, branching, floating or submerged stems with fine, thread-like roots
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Horticulturist's Insider Field Notes (No AI Fluff)

The Golden 'Finger Test' Rule

Never water on a strict calendar. Stick your index finger 2 inches into the soil. If it feels cool and damp, wait 2–3 days. If bone dry, water thoroughly until it drains from the bottom holes.

Empty the Saucer After 20 Minutes

The #1 houseplant killer is water sitting in the catch tray. Stagnant runoff water starves roots of oxygen and causes root rot.

Turn the Pot Every 2 Weeks

Houseplants naturally lean toward the nearest window light. Give the pot a quarter-turn biweekly to maintain balanced, symmetrical architecture.

Wipe the Dust Away

Dust on leaves acts like a heavy sunshade. Gently wipe broad foliage with a damp cloth monthly to maximize photosynthesis and air purification.

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Care Guide

Watering

Maintain stable water level; top up with dechlorinated water as needed

Fertilization

Diluted aquatic plant fertilizer once monthly. Use low-nitrogen aquatic fertilizer to support foliage growth without promoting algae

Aquarium water runoff:Use water from established freshwater aquariums (no added chemicals) to top up the water feature; avoid overapplication to prevent algae overgrowth
Pruning
  • Trim overgrown floating mats to maintain desired coverage and prevent overcrowding
  • Remove dead or decaying foliage promptly to prevent water fouling
  • Thin dense submerged stems to improve water circulation and light penetration
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Pet & Human Toxicity & Emergency Guide

⚠️ Toxic to Pets (Cats & Dogs)

Toxicity Warning: Veterinary toxicology registers Spiny Water-starwort (Callitriche hamulata) as possessing biochemical compounds (such as insoluble oxalates, alkaloids, or saponins) that pose ingestion hazards to felines and canines.

Feline Ingestion Risks (Cats)

Oral pain, hypersalivation (excessive drooling), pawing at mouth, swelling of tongue or lips, vocalization, and vomiting.

Canine Ingestion Risks (Dogs)

Oral mucosal irritation, gagging, retching, lack of appetite, lethargy, diarrhea, and difficulty swallowing.

Immediate Emergency First-Aid

Do NOT induce vomiting without veterinary instructions! Carefully remove remaining plant pieces, gently rinse mouth with cool water, and monitor breathing.

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Chewed leaf or stem? Open PlantFun App to scan the plant, immediately verify the botanical species, and view ASPCA toxicity severity ratings & vet first-aid advice.

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Troubleshooting & Common Plant Problems

Quick diagnostic guide for common care issues affecting Spiny Water-starwort (Callitriche hamulata):

Yellowing Leaves

Most commonly caused by overwatering or poor drainage. Ensure topsoil dries out between waterings and check for root ventilation.

Brown or Crispy Leaf Tips

Low ambient humidity, hard tap water minerals, or direct midday sunburn. Increase humidity and use filtered water.

Drooping or Wilting Foliage

Indicates dehydration or root damage from prolonged waterlogging. Inspect soil moisture and root firmness.

Common Pests (Spider Mites, Aphids)

Dry indoor air encourages pests. Wipe leaves with a damp cloth and treat with insecticidal soap or neem oil.

🌿 Instant AI Plant Health Check

Take a photo of any leaf on PlantFun App to get instant diagnosis of diseases, pests, and custom care recovery steps.

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Propagation & Repotting Guide

  • Taking Cuttings: During active spring or summer growth, take a healthy 4–6 inch cutting just below a node using clean shears.
  • Rooting Medium: Place cuttings in fresh water or moist perlite mix in bright, indirect light; refresh water weekly.
  • Potting Up: Transplant into well-draining potting mix once roots reach 2 inches in length (typically 3–5 weeks).
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Seasonal Care Calendar

  • Spring & Summer (Active Growth): Water thoroughly as topsoil dries; apply diluted balanced fertilizer monthly; encourage steady growth.
  • Autumn (Transition): Gradually reduce watering frequency as daylight hours shorten; discontinue fertilization.
  • Winter (Dormancy): Water sparingly only when soil is mostly dry; protect from cold window drafts; keep in warm room.
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Frequently Asked Questions

How often should I water my Spiny Water-starwort?

Water thoroughly when the top 1–2 inches of soil feel dry. In active growth (spring/summer), water every 1–2 weeks; reduce significantly in winter.

Where is the best indoor location for Spiny Water-starwort?

Position in bright, filtered indirect light (e.g., near an east or south-facing window with sheer curtains). Avoid harsh direct midday sun.

Is Spiny Water-starwort toxic to pets?

ASPCA: No known toxicity to cats

When should I repot my Spiny Water-starwort?

Repot every 1–2 years in spring when roots outgrow the drainage holes or the soil depletes nutrients.

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Garden Uses & Culture

Culture: N/A

Usage: Aquatic ornamental for small water features; provides shelter for small aquatic invertebrates

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