Trailing St John's-wort (Hypericum humifusum)

Trailing St John's-wort

Hypericum humifusum

It trails low across gravel, dotted with sunny yellow blooms. Prostrate perennial herb; common name: Trailing St John's-wort.

Full sun
1–2/week
Beginner
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Plant Needs

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Sunlight Full sun to partial shade; thrives in bright, direct sunlight in temperate regions, tolerates light shade during hot summer afternoons
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Watering Water when the top 2–3 cm of soil is completely dry; tolerate short periods of drought, avoid overwatering to prevent root rot
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Temperature Hardy to -10°C, suitable for temperate climates; avoid prolonged temperatures above 35°C which can cause leaf scorch
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Characteristics

  • Leaf: Opposite, oblong to oval, pale green, sessile with translucent oil glands
  • Flower: Bright yellow, 5-petaled, with dense clusters of golden stamens; 1–2 cm in diameter
  • Stem: Slender, trailing, reddish-green, rooting at nodes to form dense mats
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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

Keep soil evenly moist but not waterlogged; increase frequency during prolonged dry spells

Fertilization

Light top-dressing of compost if soil is nutrient-poor. Avoid high-nitrogen fertilizers which can promote leggy, weak growth

Crushed eggshell powder top-dressing:Sprinkle a thin layer of finely crushed eggshells on the soil surface in early spring to improve soil structure and add calcium
Pruning
  • Trim back dead or damaged foliage in early spring to encourage new growth
  • Pinch off spent flowers to prolong the blooming period
  • Thin overcrowded stems to improve air circulation and reduce disease risk
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Pet & Human Toxicity & Emergency Guide

⚠️ Toxic to Pets (Cats & Dogs)

Toxicity Warning: Veterinary toxicology registers Trailing St John's-wort (Hypericum humifusum) 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 Trailing St John's-wort (Hypericum humifusum):

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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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 Trailing St John's-wort?

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 Trailing St John's-wort?

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

Is Trailing St John's-wort toxic to pets?

ASPCA notes Hypericum species may cause mild gastrointestinal upset and increased photosensitivity if ingested

When should I repot my Trailing St John's-wort?

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: Ground cover for rock gardens, container trailing plant, and wildflower meadow addition

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