Hypericum, St John's Wort: Planting, Pruning, Care

Description and botany

The genus Hypericum comprises around 400 species of annuals, perennials, shrubs and even some small trees like H. lanceolatum reaching 10 m in height. They are found worldwide, except in deserts and Arctic regions due to differentiation during the Cretaceous period before continental separation. However, they are confined to open habitats in temperate or warm zones and tropical highlands. The genus belongs to the Hypericaceae family according to the APG III phylogenetic classification, formerly part of the Clusiaceae family.

The term millepertuis means “a thousand holes” – ‘pertuis’ referring to holes or passages in Old French. When observing a leaf of the wild herbaceous species Hypericum perforatum in particular, the lamina appears pierced with small holes which are actually glands filled with essential oil. The scientific name Hypericum, already mentioned by Pliny the Elder, refers to something entirely different – the shape of the leaves compared to heather, from the Greek hupo “almost” and ériké “heather”. Some species like H. olympicum indeed display this fine opposite foliage reminiscent of heather, though this explanation remains debated. Others suggest the etymology comes from huper and eikon meaning “above” and “image, presentation”. Hippocrates and Paracelsus mention the curative virtues of St John’s Wort used to ward off demons, likely referring to its recently recognised antidepressant effects considered preferable to Prozac®.

Hypericum flowers: ‘Magical Universe’, ‘Magical Beauty’ and ‘Blue Velvet’

The leaves have a rather graphic appearance due to being opposite, creating rungs along the stems, and sometimes whorled. The lamina varies in width, from ovate to lanceolate, triangular in x inodorum and without petiole. Hypericum x moserianum ‘Tricolor’ features dark green foliage variegated with cream white, pink and light red. H. androsaemum ‘Albury Purple’ offers beautiful green and purple hues dotted with small orange flowers paired with red berry-like fruits. H. frondosum ‘Sunburst’ stands out with its glaucous foliage. The foliage of cultivated varieties is often semi-evergreen, allowing enjoyment for much of the year with autumnal colour displays in some varieties like the completely deciduous H. reptans which turns red in autumn.

The particularly melliferous flowers are easily recognisable with their yellow to orange cup-shaped corollas, featuring a prominent tuft of stamens mixed with 3 or 5 styles. With 5 persistent sepals and 5 petals, they measure 1 to 6 cm in diameter and appear solitary or more commonly grouped in cymes at branch tips. They bloom continuously for many months between May and October depending on the variety.

The fleshy fruits, sometimes dry capsules, spherical or oval stand above the persistent calyx like a gemstone in its setting. They form while new flowers bloom, making the foliage sparkle, particularly in androsaemum and x inodorum species. Their yellow, orange, red or white hues (Hypericum x inodorum ‘Kolmawhi’ MAGICAL WHITE) eventually turn black, creating a bicoloured effect for several weeks. These berries are appreciated by birds which aid seed dispersal.

St John’s Worts have a rhizomatous root system allowing easy spread, especially in dwarf varieties. H. calycinum roots deeply, explaining its drought resistance.

St John’s Worts have very decorative foliage: Hypericum moserianum ‘Tricolor’, Hypericum inodorum ‘Rheingold’, Hypericum ‘Golden Beacon’

The berries are the icing on the cake: Hypericum inodorum ‘Magical White’ (‘Kolmawhi’)

The main varieties

Most Popular

Our Favourite Varieties

Hypericum Hidcote

Here is an all-terrain, generous bush that will thrive in all gardens, including challenging areas and dry soils. This dense, often evergreen bush with a spreading habit can reach 1 to 2 m in all directions. It provides a long flowering period from July to October, with bright golden-yellow cup-shaped flowers. The ideal plant, low-maintenance and undemanding, to plant in full sun in northern France but in partial shade in hot climates.

• Flowering time July to November
• Height at maturity 1,50 m

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Hypericum calycinum - St. John's wort

A ground-covering perennial that grows absolutely anywhere. The large, bright yellow flowers, ruffled with long central stamens, bloom all summer, borne on slender stems above evergreen green foliage.

• Flowering time July to October
• Height at maturity 35 cm

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Hypericum olympicum - St. John's wort

A deciduous undershrub that loves sun and is drought-resistant. The wide-open bright yellow flowers with a tuft of central stamens bloom in summer, borne on slender stems above small grey-green foliage. This suckering, very hardy plant forms a good small ground cover for slopes, rockeries and borders.

• Flowering time June to August
• Height at maturity 35 cm

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Hypericum kalmianum Gemo - St. John's wort

A horticultural variety developed in Denmark. A small, fast-growing bush with fairly small but numerous golden-yellow flowers. Adapts to all soils and exposures. Hardy to -15°C.

• Flowering time August to October
• Height at maturity 80 cm

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Hypericum x moserianum - St. John's wort

Here is another all-terrain, generous St John's wort that will thrive in all gardens, including challenging areas and dry soils. This semi-evergreen bush, 50 to 60 cm tall, with a spreading-rounded habit, displays slightly arching reddish stems. It provides a long flowering period from July to October, with 5 to 6 cm bright yellow cups with red anthers. The ideal plant, undemanding, to plant in full sun in northern France but in partial shade in hot climates.

• Flowering time July to November
• Height at maturity 50 cm

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Hypericum inodorum Magical Beauty Kolmbeau

Ideal in pots or along a border, this dwarf St John's wort is decorative from early summer until late autumn. In summer, its abundant golden-yellow flowers give way to numerous small shiny fruits in eggshell pink.

• Flowering time July to October
• Height at maturity 90 cm

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Hypericum inodorum Magical Red Flame KOLMAREF - St. John's wort

Very compact habit and handsome semi-evergreen foliage that resists rust well. It offers abundant bright yellow flowering followed by large clusters of red then black fruits that remain decorative until autumn. Easy to grow in ordinary well-drained soil, in sun or partial shade.

• Flowering time August to October
• Height at maturity 90 cm

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Hypericum inodorum Rheingold - St. John's wort

This shrubby St John's wort has a dense semi-upright habit and is clothed in semi-evergreen foliage, reddish-purple at bud burst, green in summer, sometimes tinged purple-violet in autumn. Its flowering is early, abundant and long-lasting, with small cup-shaped flowers producing large bright red fruits turning chocolate at ripeness.

• Flowering time June to September
• Height at maturity 1 m

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Hypericum x inodorum Magical Universe Kolmuni - St. John's wort

A bush with a dense habit and handsome deciduous dark green foliage that resists rust well. This bush offers bright yellow flowering that contrasts beautifully with its purple petioles and stems. Abundant flowering coexisting with clusters of purplish-red fruits turning brown. Easy to grow in ordinary well-drained soil, in sun or partial shade.

• Flowering time August to November
• Height at maturity 80 cm

See the product sheet

→ To choose the right variety, follow our advice: “St John’s Wort, Hypericum: Which Variety to Choose?“

Planting St John's Wort

Where to plant Hypericum?

Hypericum bushes grow effortlessly and won’t suffer from neglect, absence or beginner gardener mistakes. Exposed to full sun, wind, sea spray or cold – all tolerate frosts down to -15°C – they keep flowering, again and again… They can be grown in pots on terraces or balconies regardless of exposure. St John’s Wort thus fully deserves a place in all planted areas, even on slopes with poor soil.

You can create ground cover in sunny, partially shaded or even shaded spots if flowering isn’t essential, using stoloniferous species like calycinum, reptans, moserianum. Golden varieties like Golden Beacon® will however look prettier in partial shade, adding a lovely luminous touch. The plant can cover an area completely or fill spaces between bushes or perennials without causing excessive competition. Calycinum, androsaemum and ‘Hidcote’ tolerate shade well, meaning less than 4 hours of daily sunlight.

Shrubby specimens can be planted as standalone features if they reach 0.8 to 1 m tall, like H. ‘Hidcote’ or frondosum ‘Sunburst’. Less vigorous plants like ‘Gemo’, x inodorum or moserianum ‘Tricolor’ work better in perennial beds, rockeries or large containers.

The compact rounded clumps of Hypericum olympicum ‘Citrinum’, with large lemon-yellow flowers on blue-green stems, work well in dry rock gardens or for edging. It flowers from May to July.

When to plant?

Although potted St John’s Wort can be planted year-round, ideally it’s best done between October and March/April. Avoid planting during frost, extreme heat or when flowering.

How to plant?

Ground cover species like calycinum

• Weed the area then fork the soil to aerate to at least 20 cm deep.
• Add a few spadefuls of compost or organic fertiliser.
• Soak rootballs in a bucket of water then dig holes 30 cm apart for quick coverage.
• Position the collar level with the soil surface, backfill and firm around the plant. It shouldn’t come loose when tugged.

Shrubby species

Allow 40-60 cm around each young plant for even growth. For hedges, space vigorous plants 0.8-1 m apart.

• Soak the rootball to aid establishment.
• Backfill soil and firm gently.
• Water thoroughly.
• Apply mulch around the base to retain moisture and suppress weeds.

For container growing, add 3-4 cm drainage layer (gravel, pot shards etc). Use a mix of 1/3 garden soil, 1/3 compost and 1/3 coarse sand.

Maintenance and pruning

St John’s Wort is an easy bush that practically requires no maintenance.

Water during the first year to ensure proper establishment. Apply a complete fertiliser the following spring after cutting back any dried foliage. Potted young plants require more regular watering but will stop flowering if lacking water.

Decorative St John’s Wort berries

Pruning St John’s Wort

Dwarf (5 to 20 cm) or low-growing (30 to 50 cm) ground covers

(H. reptans, calycinum, x moserianum ‘Tricolor’)

This pruning is not obligatory but helps rejuvenate the young plant, control its spread by cutting back stolons, and maintain good density.

• Use hedge shears or secateurs once a year. Prune in late flowering in autumn for evergreen species or in late winter for deciduous species.

Shrubby species:

• Remove dead branches and those that disrupt the habit.
• Thin out occasionally with secateurs to open up the centre of the bush by cutting back half of every other branch.
• The following year, prune the remaining older branches.
• It’s also possible to cut back the entire bush completely every 5 years or so.

Potential diseases and pests

St John’s Wort may occasionally develop orange pustules on the underside of leaves. This is rust, a fungus that mainly affects forms derived from the hybrid Hypericum x inodorum (H. androsaemum X H. hircinum, found in the wild on Madeira Island). Classic St John’s Wort varieties are rarely affected, and there are resistant cultivars such as ‘Gemo’, x inodorum MAGICAL BEAUTY…

Avoid confining the young plant in damp locations, improve air circulation around the branches and prevent alternating wet and dry soil to limit the disease. Clear away pruning debris.

Propagation: propagation by cuttings, sowing, division

You can propagate St John’s Wort by sowing and propagation by cuttings. Propagation by cuttings seems to us to be the best technique, as it is simple and will produce young plants more quickly, with the assurance that they will be identical to the original variety. It is also possible to separate the stolons from running St John’s Worts.

Propagation by cuttings

Cut St John’s Wort shoots during summer and until early autumn.

1. Prepare a pot by filling it with compost mixed with sand or make your cuttings directly in the ground if it is light, after aerating it with a fork, then moisten the medium.
2. Take shoots about ten centimetres long from this year’s growth by cutting horizontally just below a node. They should be healthy and disease-free.
3. Remove the leaves near the base of the cutting, and trim the others to reduce the foliar surface. Leave only a few leaves at the top if they haven’t fallen off.
4. Make a hole in the medium using a pencil or a wooden stick.
5. Place the cutting in the hole and gently firm around it to remove air pockets and ensure good contact between the compost and the cutting.
6. Place the pot under a cold frame in a warm, bright spot but out of direct sunlight.
7. Transplant the rooted cuttings in spring into a richer medium and grow them for at least until the following spring before planting the young plants in their final position.

Sowing

St John’s Wort is sown in autumn but you are not guaranteed to obtain the selected variety you started with.

Harvest the seeds in autumn when the fruits have turned black and separate the seeds from the pulp. Rinse the seeds before storing or sowing them.

1. Prepare a pot by filling it with a special sowing compost.
2. Sow the seeds by covering them with 1 cm of soil and place them under a cold frame.
3. Water with a fine spray.

Continue to water regularly, but not excessively, to keep the medium moist. Repot the seedlings a few months after germination. After one or two years, you can plant them in their final location.

Division and layering

Carry out in autumn.

To divide a clump, separate the root ball with a sharp spade or cut with secateurs a stolon that has already produced roots to separate it from the mother plant.

To layer, bury a shoot from a deciduous plant, previously notched, and bring it back out a little further away. Wait at least 1 year before separating the layer from its mother plant.

→ Learn more in our tutorial: How to propagate St John’s Wort?

Use and pairing

The flowering of St John’s Wort offers various shades of yellow ranging from lemon yellow to orangey tones through to golden yellow. Avoid mixing warm yellows (calycinum, ‘Hidcote’) with cool, diffuse yellows such as those found in the foliage of x inodorum Golden Beacon or the flowers of olympicum ‘Citrinus’. These colours cancel each other out unless you add a touch of bluish-grey or dark green or stagger these hues over time. You could therefore border your Hypericum beds with Euphorbias and Lady’s Mantle, whose very flattering foliage flowers in chartreuse yellow tones much earlier.

A planting idea: Hypericum ‘Golden Beacon’, Euphorbia characias ssp. wulfenii, Hakonechloa macra ‘Aureola’ and Alchemilla mollis

Golden yellow pairs well with plants of similar tones such as goldenrod (Solidago), loosestrife, Kniphofia caulescens, yarrow ‘Coronation Gold’ or Rudbeckia. Remember to vary the habit of plants to create a harmonious composition. To attenuate the brightness of yellow, which can become overwhelming, combine St John’s Wort with the blue-grey tones of a Caryopteris, Perovskia or blue chaste tree (Vitex), or with the bronze hues of purple fennel or Macleaya. The purple of a Physocarpus, Cotinus coggygria ‘Rubrifolia’ or a Berberis thunbergii ‘Admiration’ or a Phormium will create an on-trend effect.

→ Discover more planting ideas with St John’s Wort in our advice sheet.