American watermilfoil

myriophyllum heterophyllum

Also known as: ["Variable watermilfoil","American milfoil"]

Family: Haloragaceae Genus: Myriophyllum Category: Herbs & Weeds

Overview

A submerged aquatic plant with feathery foliage, native to North America.

Benefits & Perks

["wildlife attractant (bees, butterflies, birds)","drought tolerant","shade tolerant"]

Botanical Classification

Phylum: Magnoliophyta
Class: Magnoliopsida
Order: Saxifragales
Family: Haloragaceae
Genus: Myriophyllum
Botanical Name: Myriophyllum heterophyllum

Plant Characteristics

Basic Information
  • Category: Herbs & Weeds
  • Suitable Location: pond margins, bog gardens, or shallow water gardens
  • Suitable For:
    Outdoor Landscapers Wildlife Supporters
  • Is Weed: No
  • Allergenicity: low
Environmental Needs
  • Climate: {"temperatureRange":"10–30°C"}
  • Hardiness: {"zones":"6–9"}
  • Misting: rarely required, only if ambient humidity is very low
  • Drainage: Fast-draining.
  • Soil Type: Well-draining potting mix with added perlite or sand.
Maintenance Level
  • Maintenance Level: moderate
  • Toughness Level: moderate
  • Pruning Frequency: As needed, typically every 2–3 months or after flowering.
  • Pruning Intensity: Light to moderate.
Care Details

Ideal Sunlight Coverage:
Bright indirect light for 6–8 hours daily; adjust for seasonal light changes.

Sunlight Tolerance Tips:
Acclimate plants gradually to intense light; avoid direct sun to prevent scorching; adjust placement between indoor and outdoor settings as needed.

Warning Signs: Yellowing leaves, root rot, or stunted growth may indicate poor soil or drainage issues.

Care Requirements

Care Difficulty
moderate

easy

Sunlight

partial shade to full sun, with protection from intense midday sun

Rotate plant for even light exposure; use sheer curtains to filter intense light; monitor for signs of light stress.

Watering

every 5–7 days, allowing soil to dry slightly between waterings

Water thoroughly until it drains from the bottom; allow topsoil to dry slightly between waterings; avoid waterlogging.

Soil

moist, loamy soil with good organic content

pH: Slightly acidic to neutral (6.0–7.0).

Ensure good aeration; avoid compacted soil; monitor moisture levels.

Temperature

Prefers 65–75°F (18–24°C); cooler temperatures in winter (50–60°F or 10–15°C) may be tolerated.

Avoid drafts; maintain stable temperatures; adjust care based on seasonal changes.

Fertilizing

every 4–6 weeks during growing season with liquid fertilizer diluted to half strength

Fertilize during active growth; avoid overfertilizing; flush soil occasionally to prevent salt buildup.

Propagation

Methods

Stem cuttings in water or moist soil.

Step-by-Step Propagation Guide
  1. Take a healthy cutting.
  2. Remove lower leaves.
  3. Place in medium.
  4. Maintain moisture and warmth.

Best Time: Spring or early summer when the plant is actively growing.

Environment

Warm, humid, and bright indirect light.

Medium

Water or a mix of peat and perlite.

Hormone

Optional but can help speed up rooting.

Timeline

Roots typically form in 2–4 weeks; new growth may take several months.

Tools Needed

Pruners, rooting hormone (optional), container, water or soil medium.

Quick Tips

Use healthy, non-flowering stems; keep cuttings out of direct sun; change water regularly if using water propagation.

Pruning & Repotting

Pruning Guide
Method

Trim back leggy stems; pinch tips to encourage branching.

Pruning Plan

Remove dead or overgrown stems to maintain shape and encourage bushier growth.

Tools

Clean pruners or scissors.

Checklist

Sanitize tools; prune dead or damaged growth; shape as desired; dispose of clippings.

Repotting Guide
Best Season

Spring, before the active growing season begins.

Pot Size

One size larger pot; ensure good drainage.

Method

Remove plant gently; trim roots if necessary; place in new pot with fresh soil; water lightly.

Suggestions

Repot every 1–2 years or when roots outgrow the pot; beneficial for growth and health.

Checklist

Choose appropriate pot; prepare new soil; handle roots carefully; water after repotting.

Advanced Care Tips

Watering Mastery
Watering Checklist

Check soil moisture; water thoroughly; ensure drainage; adjust for season.

How to Apply Water Properly

Water directly at the root zone, ensuring even moisture distribution; water early in the day to minimize evaporation; ensure proper drainage to prevent root rot.

Pro Tip: Use room temperature water to avoid shocking the roots.
Watering Schedule Tips

Water consistently to keep soil moist but not waterlogged; adjust frequency based on season (more in growing season, less in winter).

Soil Improvement

Add perlite or sand for drainage; incorporate organic matter for fertility.

Temperature Stress Management
Signs of Temperature Issues

Wilting, leaf drop, or chlorosis in cold; scorching or stunted growth in excessive heat.

Cold Stress

Slows growth, may cause root damage, and increases susceptibility to disease.

Solution: Move to a warmer location; insulate roots; avoid overwatering in cold conditions.

Hot Stress

Leaves may scorch, growth may slow, and water loss increases.

Solution: Provide shade; increase humidity; water more frequently but avoid waterlogging.

Fertilizing Guide
Fertilizing Checklist

Check fertilizer type; dilute correctly; apply during growing season; monitor for signs of overfertilization.

Fertilizing Method

Use a balanced liquid fertilizer diluted to half strength every 4–6 weeks during growing season; reduce or stop in winter.

Common Problems & Solutions

Yellowing leaves in Myriophyllum heterophyllum may indicate nutrient deficiencies, such as iron or nitrogen, or stress from poor water quality, light deprivation, or pathogen infection.

Wilting in Myriophyllum heterophyllum is often a sign of inadequate water uptake, possibly due to root damage, water stress, or environmental factors like high temperatures or low humidity.

Leaf spots on Myriophyllum heterophyllum may be caused by fungal or bacterial pathogens, resulting in necrotic lesions that can impair photosynthesis and weaken the plant.

Rotting, particularly root or stem rot, can occur in Myriophyllum heterophyllum due to overwatering, poor drainage, or fungal infections, leading to tissue decay and plant decline.

Toxicity Warning

Cats
Slightly Toxic

Myriophyllum heterophyllum is slightly toxic to cats. Ingestion may lead to mild gastrointestinal irritation, but severe toxicity is uncommon. The plant's compounds can cause discomfort if consumed.

⚠️ Symptoms:
vomiting diarrhea depression
🌿 Toxic Parts:
entire plant
⚡ Toxic If:

if eaten

Prevent cats from accessing this plant. Seek veterinary advice if ingestion is suspected.
Dogs
Slightly Toxic

Myriophyllum heterophyllum is slightly toxic to dogs. Consumption can cause mild gastrointestinal upset, though severe poisoning is rare. The plant contains compounds that may irritate the digestive system of dogs.

⚠️ Symptoms:
vomiting diarrhea lethargy
🌿 Toxic Parts:
entire plant
⚡ Toxic If:

if eaten

Keep pets away from this plant. If ingestion occurs, consult a veterinarian promptly.
Humans
Slightly Toxic

Myriophyllum heterophyllum, commonly known as Carolina watermilfoil, is considered slightly toxic to humans. Ingestion can lead to mild gastrointestinal discomfort due to the presence of certain compounds that may irritate the digestive tract.

⚠️ Symptoms:
nausea stomach discomfort diarrhea
🌿 Toxic Parts:
entire plant
⚡ Toxic If:

if eaten

Avoid ingestion of this plant. Wash hands thoroughly after handling to prevent accidental ingestion.
Important: Keep this plant out of reach of children and pets. If ingestion occurs, contact poison control or veterinary services immediately.

Frequently Asked Questions

Q: Is Myriophyllum heterophyllum invasive?

A: Yes, it is considered invasive in many regions due to its rapid growth and ability to outcompete native aquatic plants.

Q: Can this plant be grown in aquariums?

A: Yes, it is commonly used in aquariums for its decorative foliage and oxygenating properties.

Q: Does it require special care?

A: It thrives in still or slow-moving water with moderate light and nutrient levels, but can be sensitive to water chemistry changes.

Quick Reference
Family: Haloragaceae
Care: moderate
Light: partial shade to full sun, wit
Water: every 5–7 days, allowing soi
Suitable For: ["outdoor landscapers","wildlife supporters (attracts bees, butterflies, birds)"]
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