Common Duckweed (Lemna minor)

Common Duckweed

Lemna minor

Tiny floating fronds carpet still water like living confetti. Aquatic floating perennial; common name: common duckweed.

Partial sun
N/A/week
Beginner
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Plant Needs

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Sunlight Tolerates partial shade to full sun; avoid intense midday direct sun to prevent frond scorching
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Watering Requires constant access to still, clean freshwater; maintain stable water levels to support mat growth
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Temperature Thrives in 15–25°C; tolerates brief drops to 5°C but cannot survive freezing conditions
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Characteristics

  • Frond (Leaf): Oval to rounded bright green fronds, 1–3 per individual plant; most have one fine, thread-like root
  • Flower: Inconspicuous tiny greenish flowers enclosed in a membranous sac; rarely produced in cultivation
  • Growth Habit: Spreads rapidly to form dense floating mats on still freshwater surfaces
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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

Top up water levels as needed to maintain consistent depth; test monthly for pH balance

Fertilization

Diluted aquatic plant feed every 2 weeks. Avoid over-fertilization to prevent harmful algal blooms that can outcompete duckweed

Compost vegetable tea:Steep fully composted vegetable scraps in water for 3 days, dilute 1:20 before adding to water features; discard solid scraps to avoid water contamination
Pruning
  • Thin dense frond mats to prevent oxygen depletion in underlying water
  • Skim discolored or decaying fronds to maintain water clarity
  • Remove excess growth to avoid covering the entire water surface, which can block light for submerged aquatic life
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Pet & Human Toxicity & Emergency Guide

🟢 Pet-Safe (Non-Toxic to Cats & Dogs)

Pet Safety Verified: According to clinical veterinary databases (ASPCA), Common Duckweed (Lemna minor) is non-toxic to both cats and dogs, making it an excellent choice for pet-friendly homes.

Pet Tolerance

Leaves, stems, and flowers contain no systemic toxins or hazardous oxalates; safe for curious puppies and kittens.

Mild Fiber Sensitivity

While non-toxic, excessive consumption of fibrous leaves may cause mild, temporary stomach upset or regurgitation.

Recommended Placement

Safe for low tables, living rooms, and active pet environments.

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Troubleshooting & Common Plant Problems

Quick diagnostic guide for common care issues affecting Common Duckweed (Lemna minor):

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.

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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 Common Duckweed?

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 Common Duckweed?

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

Is Common Duckweed toxic to pets?

ASPCA-verified non-toxic to cats; no toxic compounds identified

When should I repot my Common Duckweed?

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 cover for pond wildlife; natural water filtration; supplemental feed for waterfowl and fish

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