Hypericum calycinum, St. John's wort
Vines & Groundcovers

Hypericum calycinum

St. John's wort

Hypericaceae

Southeastern Europe and southwestern Asia, including Bulgaria, Turkey, and the Republic of Georgia

At a Glance

TypeShrub
HabitSpreading
FoliageSemi-evergreen
Height12-18 inches (30-46 cm)
WidthSpreading indefinitely by runners
Maturity3 years

Growing Zones

USDA Hardiness Zones

5 - 9
Zone 5
Zone 6
Zone 7
Zone 8
Zone 9
These zones indicate the coldest temperatures this plant can typically survive.
Frost Tolerancehardy

Key Features

Attracts Pollinators
Attracts Butterflies
Deer Resistant
Drought Tolerant
Maintenancelow

Overview

A low-growing, semi-evergreen to evergreen sub-shrub reaching 12–18 inches (30–46 cm) tall and spreading indefinitely by stoloniferous runners to form dense mats. Stems are square in cross-section, green to reddish-brown, upright to slightly arching. Leaves are opposite, simple, oblong to ovate, 2–4 inches (5–10 cm) long and 0.75–1.5 inches (2–4 cm) wide, blue-green above, paler beneath, with translucent glandular dots visible when held to light—a characteristic of the genus. Flowers are solitary or in few-flowered cymes at stem tips, 2–3 inches (5–8 cm) across, with 5 bright yellow petals and a central mass of approximately 200 stamens that radiate outward 0.75–1 inch (2–2.5 cm) long. Bloom period extends from June through September in zones 6–8. Growth rate is moderate to fast; a single plant fills a 3-foot (0.9 m) area within 2 years via underground runners. Foliage is evergreen in zones 8–9, semi-evergreen in zone 7, and dies back to the ground in zones 5–6, regrowing from the roots. Leaves may develop purplish-red discoloration in cold weather. Spreads aggressively in favorable conditions and may displace adjacent plantings if not edged or contained.

Native Range

Native to southeastern Europe and southwestern Asia, including Bulgaria, Turkey, and the Republic of Georgia. Found in dry, rocky scrubland, open woodland understory, and forest margins at elevations up to 3,000 feet (900 m).

Suggested Uses

Commonly planted as a groundcover on slopes, under trees, and in dry shade areas where other plants fail, at 18–24 inch (46–61 cm) spacing for full coverage within 2 years. Used for erosion control on banks and hillsides due to its dense mat of roots and runners. Suitable for planting between stepping stones, along foundation edges, and in parking strip plantings where mowing is not practical. Spreading habit is problematic in mixed perennial borders or near slow-growing plants.

How to Identify

Identified by its low, spreading habit with square stems and opposite, oblong to ovate leaves 2–4 inches (5–10 cm) long that are blue-green and show translucent glandular dots when held to light. Flowers are 2–3 inches (5–8 cm) across—noticeably larger than most other Hypericum species—with 5 bright yellow petals and a prominent central brush of approximately 200 stamens radiating outward. The stoloniferous spreading habit forming dense ground-level mats distinguishes it from upright Hypericum species.

Appearance

Size & Dimensions

Height1' - 1'6"
Width/Spread2' - 4'

Reaches mature size in approximately 3 years

Colors

Flower Colors

yellow

Foliage Colors

blue green
purple red

Fall Foliage Colors

purple
red

Bloom Information

Bloom Period

~12 weeks
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SummerFall
Flowers from June through September in zones 6–8, with peak bloom in July. Individual flowers last 3–5 days; new flowers open continuously over the bloom period. In zones 9–10, flowering may begin in May and taper off in August heat. Plants in deep shade produce fewer flowers with extended internodes. A second flush of lighter bloom may occur in early fall after mid-summer deadheading.

Detailed Descriptions

Flower Description

Bright yellow

Foliage Description

Blue-green above, paler beneath; may develop purplish-red tones in cold weather

Growing Conditions

Sun Requirements

Full Sun
Partial Shade
Full Shade
Requires 2-8 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.5(Neutral)
357912
Soil Types
clayloamsandchalkrocky
Drainage
average

Water & Climate

Water Needs

Low

Frost Tolerance

hardy

Time to Maturity

2-3 years to full groundcover density

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Water weekly during the first growing season to establish the root system and runners. Established plants tolerate prolonged dry periods of 4–6 weeks but may defoliate partially in severe drought; foliage recovers with fall rains. Tolerates a wide range of soils including clay, sand, and poor rocky substrates; drainage is not critical. No fertilization required in most soils—excess nitrogen promotes rank vegetative growth at the expense of flowering. Monitor spreading runners and install a root barrier or edge along walkways, beds, and lawn borders to prevent encroachment. Leaf spot fungus (Septoria) and rust may develop on foliage in humid conditions; affected leaves develop brown or orange spots and drop prematurely. Deer tend to avoid this species.

Pruning

Cut all stems to 2–3 inches (5–8 cm) above ground level in late winter or early spring before new growth emerges. This annual cutback removes winter-damaged foliage and promotes compact, dense regrowth with improved flowering. Unpruned plants become leggy and sparse at the base within 2–3 years. Where the plant has spread beyond its intended area, dig and remove runner sections in spring or fall.

Pruning Schedule

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late spring

Maintenance Level

low

⚠️ Toxicity Warning

Toxic to pets