Does it need a lot of water?

Yes, it prefers consistently moist to wet soil.

Can I grow it in a regular garden bed?

Only if you can keep the soil very damp, as it is a wetland specialist.

Plant guide

Square-stalked St. John's-wort.

Hypericum tetrapterum

Pronounced hy-PEER-ih-kum tet-RAP-ter-um

Also known as Square St. John's Wort, Square Stemmed Saint John's Wort, Square-stalked St John's-Wort, St. Peter's-wort, four-winged St. John's-wort

Hypericum tetrapterum — Photo by Reiner Richter (CC BY) via gbif

This charming perennial loves damp spots and is often found near streams or marshes. It is quite a hardy plant that brings a lovely yellow touch to wetter areas of your garden. You will enjoy its unique appearance as it settles into its environment.

At a glance

Care level: Easy
Plant type: Perennial
Light: Full sun to partial shade
Indoor light: Bright indirect
Water: Every 2 to 4 days
Mature size: 2 to 3 feet
Growth rate: Medium
Hardiness: USDA 5 to 9
Bloom time: Mid to late summer

Care

Keep the soil consistently moist to mimic its natural wetland habitat. Watch for wilting if the ground dries out too much. It is a very resilient plant that does not require much fuss.

Watering: Ensure the soil stays damp at all times.
Feeding: A light feeding during the growing season is plenty.
Pruning: Trim back dead stems in late winter to encourage new growth.
Repotting: Repot only if the plant becomes root bound in its container.
Soil: Moist to wet soil
Soil pH: Neutral to slightly acidic
Temperature: -29 to 30°C
Humidity: 40 to 80%

Safety

People: The plant contains hypericin, which can cause photosensitivity if ingested or handled frequently.
Pets: This plant can be toxic to cats and dogs if ingested.
Children: Keep this plant away from children due to the potential for skin irritation and toxicity if ingested.
Contact allergens: Contact with the sap may cause skin irritation or increased sensitivity to sunlight.
Airborne allergens: There is no significant evidence of respiratory allergies associated with this plant.
Edibility: This plant is not intended for human consumption.

How to identify it

Distinctive four winged stems
Small yellow five petaled flowers
Opposite leaves with translucent dots
Grows in damp or wet soil

Height: 0.3 to 0.8m
Spread: 0.2 to 0.5m
Leaves: green, deciduous
Flowers: yellow, 1 to 2cm
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, cuttings, division
When to plant: spring, autumn

Group this plant with other moisture-loving species to create a balanced bog garden ecosystem.

Grows well with

Purple Loosestrife · They share similar moisture requirements in a wetland setting.
Marsh Marigold · Both thrive in the damp, boggy conditions this plant prefers.

Similar species

Common St. John's Wort · It is a related species but lacks the distinct square, winged stems.

Science

Family: Hypericaceae
Genus: Hypericum
Order: Malpighiales
Class: Magnoliopsida
Native range: Europe, Western Asia, and North Africa.
Conservation: This plant is common in its native range and is not currently listed as endangered.

It grows in wet meadows and stream banks where it can access constant moisture.

Value to wildlife: nectar source
Pollinators: bees, butterflies
Uses: wetland restoration, bog gardens, pollinator gardens

Through the year

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Flowering

Fruiting

Foliage

Ecological indicators

Salinity: 1/9
Soil reaction: 6/9
Light: 6/9
Temperature: 5/9
Moisture: 8/9
Nutrients: 5/9

Taxonomy resolved against GBIF.

Questions people ask

Does it need a lot of water?: Yes, it prefers consistently moist to wet soil.
Can I grow it in a regular garden bed?: Only if you can keep the soil very damp, as it is a wetland specialist.

Where the name comes from

The name Hypericum is ancient Greek, while tetrapterum refers to the four-winged stems.

Good to know

It is commonly known as the square-stalked St. John's wort.
The stems have four distinct wings or ridges.
It thrives in damp, marshy ground where other plants might struggle.
The flowers are small but appear in dense, attractive clusters.

Also in

Plants toxic to cats and dogs

Keep your square-stalked st. john's-wort growing

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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.