Common St. John's wort (Hypericum perforatum)

Also known as: Triptonweed

**Common Tansy (Tanacetum vulgare)** is a plant native to Europe and Central Asia. It poses a risk to livestock due to its toxicity, and it can also be harmful to humans if ingested. This rapidly spreading plant has established itself in North America and Australia, where it is often regarded as an invasive species.

In This Article

Care Tips Water Sunlight Temperature Soil Fertilize Prune Propagation Repotting Toxicity

Attributes of Common St. John's wort

Lifespan

Perennial

Plant Type

Herb

Plant Height

30 cm to 1 m

Spread

30 cm to 60 cm

Leaf Color

Green

Flower Size

2 cm to 3.5 cm

Flower Color

Yellow Gold

Images of Common St. John's wort

Quickly Identify Common St. John's wort

Yellow flowers with black dots, clusters of showy stamens.

Perforated leaves with translucent and black dots.

3-celled seed capsule with flattened black seeds.

New stems ridged, maturing to smooth, woody brown.

Rhizomatous root system for rapid natural propagation.

Scientific Classification of Common St. John's wort

Phylum

Vascular plants

Class

Dicotyledons

Order

Malpighiales

Family

St. John's wort

Genus

St. John's worts

Species

Common St. John's wort

Planting and Growing of Common St. John's wort

Care Difficulty

Easy

Watering Schedule

Every 4 days

Sunlight Requirements

Full sun

Sunshine Duration

6-10 hours

Ideal Temperature

65-75℉

Soil Type

Potting Mix, Peat Mix

Soil pH

6.5-7.5

Fertilizer Type

Balanced

Pruning Season

Spring, Summer

Pruning Area

Branches, Leaves

Pruning Frequency

2 times a year

Repotting Season

Spring

Pot Type

Plastic, Ceramic

How to Water Common St. John's wort?

Hypericum perforatum requires a balanced watering approach. Ensure that the soil is moist but not waterlogged. The recommended amount during each watering is approximately 250 milliliters, aiming to soak the soil without causing standing water. This ensures the roots access necessary moisture while preventing root rot.

What are the symptoms of an underwatered Common St. John's wort? ›

What should I do if my Common St. John's wort is not getting enough water? ›

What are the symptoms of an overwatered Common St. John's wort? ›

How to save an overwatered Common St. John's wort? ›

What Are the Sunlight Requirements for Common St. John's wort?

Sunlight Requirements: Full sun, Partial sun

Duration of light: 5-8 hours a day

Partial to full sun is ideal for Hypericum perforatum, as it encourages vibrant blooms and vigorous growth. This setup ensures sufficient energy intake for photosynthesis.

What is the best location for planting Hypericum perforatum? ›

How to ensure proper lighting indoor? ›

What environmental factors should be considered? ›

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What Is the Ideal Temperature Range for Common St. John's wort?

Ideal Temperature: 65 ~ 75℉

Hypericum perforatum, commonly known as St. John's Wort, thrives best in a temperature range of 65 to 75°F. These conditions mimic its natural habitat in temperate regions where moderate temperatures are the norm. Keeping the plant within this range helps ensure optimal growth and flowering, as well as robust leaf development and vibrant coloration. If you can maintain these temperatures consistently, the plant will likely show its best performance.

What Soil is Best for Common St. John's wort?

Soil type: Loam, Sandy loam, Calcareous soil

Soil PH: 6.5 ~ 7.5

Hypericum perforatum thrives in well-draining soil to prevent root rot. Ensuring soil has good drainage enhances the plant's growth by allowing roots to receive necessary oxygen while avoiding waterlogging. While not overly demanding, Hypericum perforatum benefits from soil with moderate nutrients. A balance of organic matter in the soil can improve plant vigor and support sustained blooming throughout the growing season. Preferring a soil pH of 6.5 to 7.5, this plant thrives in neutral to slightly alkaline conditions. Such pH levels facilitate optimal nutrient absorption, ensuring robust plant health and vibrant flower production. More About Soil→

How to Fertilize Common St. John's wort?

Fertilizer type: Balanced

Hypericum perforatum benefits from a balanced fertilization regimen. For liquid fertilizers, mix a water-soluble fertilizer at half the recommended strength to avoid over-fertilization. Use approximately 1 liter of this diluted solution per plant during each application to ensure nutrient availability without overwhelming the roots. More About Fertilizing Techniques→

How to Prune Common St. John's wort?

Pruning Time: Spring, Summer, Autumn

Start by cutting away any dead, damaged, or weak stems at the base. This helps the plant focus its energy on new, healthy growth, resulting in a more vigorous bush. Trim back any overgrown branches to maintain your desired shape. Aim for a rounded, bushy appearance. Removing crowded areas improves air circulation, reducing the likelihood of fungal diseases.

How to Propagate Common St. John's wort plant?

Propagate Time: Spring, Early summer, Early autumn

Sow seeds in a seed tray filled with a quality seed-starting mix. Lightly cover with soil, as seeds need light for germination. Keep the soil moist but not waterlogged.

Select healthy, non-flowering stems and cut sections about 4 inches long. Remove leaves from the lower half and dip the end in rooting hormone to encourage faster root development.

Divide established plants in early spring or during dormant periods. Use a sharp spade to carefully lift a clump, ensuring each section has roots and shoots for successful establishment.

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How to Repot Common St. John's wort plant?

Repotting frequency: Every 2-3 years

Hypericum perforatum shows it's time for a repot when you notice roots protruding from the drainage holes or if the plant appears to dry out more quickly than usual after watering. Spring is ideal because the plant begins its active growth phase, adapting well to the new environment.

Select a pot that is about 2 inches larger in diameter than the current one. Ensure it has good drainage holes to prevent waterlogging. A larger pot will accommodate future growth and prevent the roots from becoming bounded, promoting healthier development.

Opt for a well-draining garden soil mixed with sand or perlite. This blend ensures adequate aeration and prevents root rot. Good drainage is crucial for preventing over-saturation, allowing the plant to thrive in its new setup.

Toxicity of Common St. John's wort

Is Common St. John's wort toxic to humans?

Common St. John's wort has the potential to trigger negative reactions in individuals who are allergic to the plant or are using prescription medications that may interact with it. Both the leaves and flowers of the plant, as well as products containing these parts, can lead to adverse effects through external application or internal consumption. Signs of an allergic response may range from mild to moderate symptoms, including nausea, abdominal discomfort, reduced appetite, diarrhea, dizziness, fatigue, headaches, dry mouth, confusion, sedation, sensitivity to light, and feelings of restlessness. When combined with prescription medications, especially antipsychotics, antidepressants, anticoagulants, and contraceptive drugs, common St. John's wort may lead to serious or potentially life-threatening side effects.

Is Common St. John's wort toxic to cat?

The tissues of the commonly known St. John's wort plant (Hypericum perforatum) are seen as hazardous to felines, as they have the potential to disrupt hormonal levels, leading to unpredictable behavior. It is crucial to seek immediate treatment for a cat at a veterinary facility if even a tiny quantity is ingested, since just nibbling on the leaves may result in negative reactions.

Is Common St. John's wort toxic to dog?

Common St. John's wort poses mild toxicity risks to dogs. Physical contact with any aerial portion of the plant can lead to contact dermatitis, with more serious instances potentially resulting in skin ulcers or blisters. Ingesting the plant may result in fever, gastrointestinal upset, and photosensitivity, which can cause aversion to bright light; in severe cases, it is possible for temporary blindness to occur. Fortunately, the majority of cases of St. John's wort poisoning are mild and typically resolve within a few days.

WARNING

The judgment on toxicity and danger is for reference only. We DO NOT GUARANTEE any accuracy of such judgment. Therefore, you SHALL NOT rely on such judgment. It is IMPORTANT TO SEEK PROFESSIONAL ADVICE in advance when necessary.

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