Yes, it is very hardy and often grows as a weed in disturbed soils.

Does it need full sun?

It prefers full sun to light shade for the best flowering.

Plant guide

St. John's wort.

Hypericum perforatum

Pronounced hy-PEER-ih-kum per-for-AY-tum

Also known as Common St. John's Wort, Common St. Johnswort, Gammock, Goatweed, Herb-John, Klamath Weed, Klamathweed

Common St. John's Wort — Photo by Sophia K (CC BY) via iNaturalist

St. John's wort is a cheerful perennial known for its bright yellow flowers and medicinal history. It spreads easily and is often found growing wild in meadows or along roadsides. You'll love how its sunny blooms brighten up a garden space.

Another photo of St. John's wort — Photo by Alan Prather (CC BY) via iNaturalist

At a glance

Care level: Easy
Plant type: Herbaceous perennial
Light: Full sun to partial shade
Indoor light: Direct sun
Water: Every 7 to 14 days
Mature size: 1 to 3 feet
Growth rate: Fast
Hardiness: USDA 3 to 9
Bloom time: Early to late summer

Care

Give this plant plenty of sun and well draining soil to keep it happy. Watch for wilting if the soil dries out too much, though it is quite hardy. Keep an eye on its spread as it can become invasive in some areas.

Watering: Water when the top inch of soil feels dry to the touch.
Feeding: Apply a balanced fertilizer once in early spring to support new growth.
Pruning: Cut back the stems in late autumn or early spring to encourage a bushier shape.
Repotting: Repot only if the plant becomes root bound or you need to divide the clump.
Soil: Well draining, sandy or rocky soil
Soil pH: 6.0 to 7.5
Temperature: -25 to 35°C
Humidity: 40 to 70%
Drought tolerance: High
Lifespan: Perennial, typically 5 to 10 years
Deer and rabbits: High

Signs it needs repotting

Roots growing out of the drainage holes.
Water sitting on the surface for too long.

Safety

People: The plant is considered toxic if ingested and can cause skin irritation or increased sensitivity to sunlight.
Pets: This plant is toxic to cats, dogs, and horses if ingested.
Children: Keep this plant away from children as ingestion of any part can lead to illness and skin sensitivity.
Contact allergens: Handling the foliage can cause contact dermatitis in sensitive individuals due to the oils.
Airborne allergens: The pollen may trigger mild allergic reactions in some people during the peak summer bloom.
Edibility: This plant contains hypericin, which can cause severe photosensitivity in humans and livestock if ingested.

How to identify it

Bright yellow five petaled flowers
Translucent dots on leaf surfaces
Opposite leaves along the stem
Stems have two distinct ridges

Height: 0.3 to 0.9m
Spread: 0.3 to 0.6m
Leaves: green, deciduous
Flowers: yellow, 2 to 3cm
Fruit: brown, Autumn

Problems to watch for

Rust · Fungal infection causing orange spots on the undersides of leaves.

By symptom

Plant problems by symptom

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Growing it

Propagation: seed, division
When to plant: spring, autumn
Overwintering: Cut the stems back to the ground in late autumn or early winter. The plant will naturally go dormant and return in spring.
In containers: It grows well in containers, but ensure the pot has excellent drainage to prevent root rot.

Division

1. Dig up the clump in early spring.
2. Use a sharp spade to divide the root ball into smaller sections.
3. Replant immediately in well drained soil.

Pair this plant with other drought tolerant perennials to create a low maintenance meadow garden.

Grows well with

Yarrow · They share similar sun and soil requirements.
Lavender · Both plants enjoy well drained soil and full sun.

Similar species

Shrubby St. John's Wort · This is a woody shrub version rather than a herbaceous perennial.

Science

Family: Hypericaceae
Genus: Hypericum
Order: Malpighiales
Class: Magnoliopsida
Native range: Europe, parts of Asia, and Northern Africa.
Conservation: It is considered an invasive weed in many parts of the world, including North America and Australia.

It thrives in open, sunny fields and disturbed ground where it outcompetes native vegetation.

Value to wildlife: pollen source
Pollinators: bees, butterflies, beetles
Uses: herbal medicine, ground cover, pollinator gardens

Through the year

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Flowering

Fruiting

Foliage

Ecological indicators

Salinity: 2/9
Soil reaction: 6/9
Light: 7/9
Temperature: 5/9
Moisture: 4/9
Nutrients: 3/9

Taxonomy resolved against GBIF.

Questions people ask

Is it easy to grow?: Yes, it is very hardy and often grows as a weed in disturbed soils.
Does it need full sun?: It prefers full sun to light shade for the best flowering.

Where the name comes from

The genus name Hypericum comes from Greek words meaning over an apparition, while perforatum refers to the leaf glands that look like pinpricks.

Good to know

It has been used for centuries in traditional medicine.
The yellow flowers produce a red pigment when crushed.
It is known as St. John's Wort because it traditionally blooms around St. John's Day in June.
The plant can spread rapidly through underground runners.

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This guide was generated with AI on October 19, 2026 and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.