Kalm's St. John's Wort
hypericum kalmianum
Also known as: ["Kalm's St. Johnswort","Kalm's Hypericum"]
Overview
A deciduous shrub native to North America, valued for its bright yellow flowers and medicinal properties.
Benefits & Perks
["long-flowering","wildlife attractant (bees, butterflies, birds)","drought tolerant"]
Botanical Classification
| Phylum: | Magnoliophyta |
| Class: | Magnoliopsida |
| Order: | Malpighiales |
| Family: | Hypericaceae |
| Genus: | Hypericum |
| Botanical Name: | Hypericum kalmianum |
Plant Characteristics
Basic Information
- Category: Shrubs
- Suitable Location: border plantings, rock gardens, or as a specimen shrub in open spaces
- Suitable For:
- Is Weed: No
- Allergenicity: low
Environmental Needs
- Climate: {"temperatureRange":"–34–29°C"}
- Hardiness: {"zones":"3–7"}
- Misting: rarely required, only if ambient humidity is very low
- Drainage: Fast-draining to prevent root rot.
- Soil Type: Well-draining, loamy soil with organic matter. Avoid heavy clay.
Maintenance Level
- Maintenance Level: moderate
- Toughness Level: moderate
- Pruning Frequency: Annually, immediately after flowering.
- Pruning Intensity: Moderate; remove up to one-third of old growth if needed.
Care Details
Ideal Sunlight Coverage:
Full sun (6–8 hours of direct sunlight daily). Tolerates partial shade but may produce fewer flowers.
Sunlight Tolerance Tips:
Acclimate plants gradually to intense sunlight if moved from shade. Protect from harsh afternoon sun in hot climates to prevent scorching. Outdoor placement is ideal, but ensure adequate light indoors if grown as a container plant.
Care Requirements
Care Difficulty
moderatemoderate
Sunlight
full sun to partial shade
Rotate plant for even light exposure; use sheer curtains to filter intense sun; supplement with grow lights if indoors.
Watering
every 7–10 days during active growth, less frequently in winter
Water thoroughly but infrequently; ensure soil dries slightly between waterings; avoid waterlogging.
Soil
well-drained, loamy soil with moderate fertility
pH: Slightly acidic to neutral (pH 6.0–7.0).
Ensure pots have drainage holes; avoid overwatering; amend heavy soil with organic matter.
Temperature
Hardy in USDA zones 3–7. Prefers cool to moderate temperatures (60–75°F or 15–24°C). Tolerates cold winters but requires protection from extreme heat.
Avoid placing near heat sources; protect from late spring frosts; ensure good air flow in summer.
Fertilizing
every 4–6 weeks during spring and summer
Avoid over-fertilizing, which can harm roots; fertilize before new growth emerges; flush soil occasionally to prevent salt buildup.
Propagation
Methods
Stem cuttings taken in late spring or early summer.
Step-by-Step Propagation Guide
- Take 4–6 inch cuttings.
- Remove lower leaves.
- Dip in rooting hormone.
- Plant in medium.
- Maintain humidity.
- Transplant when rooted.
Best Time: Late spring to early summer when new growth is firm but not woody.
Environment
High humidity (70–90%), indirect light, and consistent warmth (65–75°F or 18–24°C).
Medium
Peat-based mix with perlite or sand for good drainage.
Hormone
Rooting hormone is recommended to improve success rates.
Timeline
Roots develop in 4–8 weeks; establish in new pots after 3–6 months.
Tools Needed
Pruning shears, rooting hormone, small pots, misting spray bottle, plastic bags or propagation dome.
Quick Tips
Use healthy, non-flowering stems; maintain consistent moisture; provide bottom heat if possible.
Pruning & Repotting
Pruning Guide
Method
Selective thinning of branches; heading back to encourage denser growth.
Pruning Plan
Prune to maintain shape, encourage bushiness, and remove dead or weak growth. Best done after flowering to preserve buds for the next season.
Tools
Sharp bypass pruners, loppers for larger branches, gloves.
Checklist
Prune after flowering; sterilize tools; remove dead/damaged wood; shape evenly.
Repotting Guide
Best Season
Early spring before new growth begins.
Pot Size
Move to a pot one size larger (2–3 inches in diameter) than the current one.
Method
Remove plant gently; trim roots if crowded; replace with fresh, well-draining soil; ensure pot has drainage holes.
Suggestions
Repot every 2–3 years or when roots fill the container. Necessary to refresh soil and provide space for growth.
Checklist
Choose appropriate pot size; use fresh soil mix; trim roots if needed; water after repotting.
Advanced Care Tips
Watering Mastery
Watering Checklist
Check soil moisture before watering; water deeply; ensure drainage; avoid wetting foliage.
How to Apply Water Properly
Water at the base of the plant, ensuring moisture reaches the root zone. Water early in the morning to minimize evaporation and fungal risk. Allow excess water to drain freely from the soil.
Watering Schedule Tips
Water deeply once every 7–10 days during active growth, reducing frequency to every 2–3 weeks in winter. Adjust based on rainfall and soil moisture retention.
Soil Improvement
Add compost or aged manure for fertility; mix in perlite or sand for drainage; avoid compacting soil.
Temperature Stress Management
Signs of Temperature Issues
Chlorosis or leaf scorch in excessive heat; leaf drop or stunted growth in prolonged cold.
Cold Stress
Low temperatures slow growth but are generally tolerated due to hardiness. Prolonged freezing without protection can damage buds or stems.
Solution: Mulch heavily around the base in fall; protect container plants by moving them to sheltered locations; avoid overwatering before freezes.
Hot Stress
Excessive heat can cause wilting, leaf scorch, or reduced flowering. Heat stress is more likely in poorly drained soil or high humidity.
Solution: Provide afternoon shade in hot climates; water deeply to cool roots; improve air circulation around the plant.
Fertilizing Guide
Fertilizing Checklist
Use balanced fertilizer; apply in spring; avoid winter feeding; monitor for salt buildup.
Fertilizing Method
Use a balanced, slow-release fertilizer in early spring. Apply a diluted liquid fertilizer monthly during growing season, avoiding winter.
Common Problems & Solutions
Toxicity Warning
Cats
Slightly ToxicCats may experience mild gastrointestinal upset and photosensitivity if they consume Hypericum kalmianum berries. The toxic effects are generally mild but can cause discomfort, particularly in sensitive individuals.
⚠️ Symptoms:
🌿 Toxic Parts:
⚡ Toxic If:
if eaten
Dogs
Slightly ToxicIn dogs, ingestion of Hypericum kalmianum berries may lead to mild gastrointestinal distress and potential photosensitivity. The toxic compounds primarily affect the digestive system and can cause discomfort, though severe reactions are rare.
⚠️ Symptoms:
🌿 Toxic Parts:
⚡ Toxic If:
if eaten
Humans
Slightly ToxicHypericum kalmianum contains hypericin and other compounds that can cause mild gastrointestinal upset and photosensitivity when ingested in significant quantities. The physiological impact is generally limited to mild irritation of the digestive tract and increased sensitivity to sunlight.
⚠️ Symptoms:
🌿 Toxic Parts:
⚡ Toxic If:
if eaten
Frequently Asked Questions
Q: Is Hypericum kalmianum toxic to pets?
A: It is mildly toxic to dogs and cats if ingested.
Q: Does Hypericum kalmianum attract wildlife?
A: Yes, it attracts bees, butterflies, and birds with its flowers.
Q: How often should Hypericum kalmianum be watered?
A: Water moderately, allowing the soil to dry slightly between waterings.
Quick Reference
| Family: | Hypericaceae |
| Care: | moderate |
| Light: | full sun to partial shade |
| Water: | every 7–10 days during activ |
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