Hypericum olympicum f. uniflorum 'Citrinum'

RHS Plant Profile

St John's wort 'Citrinum'

RHS 1999

Synonyms

Hypericum olympicum 'Citrinum'

Alpine Rockery Shrubs

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A deciduous dwarf shrub with upright stems bearing small, ovate, grey-green leaves, and small terminal clusters of pale lemon-yellow flowers to 3.5cm wide in summer

Position

Full sun, Partial shade

Soil Types

Chalk, Clay, Loam, Sand

Max Height

0.1-0.5 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity: 2–5 years
Max Spread: 0.1-0.5 metres
Max Height: 0.1-0.5 metres

Growing Conditions

Chalk Clay Loam Sand

Moisture: Moist but well–drained or Well–drained
pH: Acid or Alkaline or Neutral

Position

Full sun Partial shade

Aspect: South–facing or East–facing or West–facing
Exposure: Exposed or Sheltered
Hardiness

Hardiness Ratings

All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets

H1A: under glass all year (>15C)
H1B: can be grown outside in the summer (10 - 15)
H1C: can be grown outside in the summer (5 - 10)
H2: tolerant of low temperatures, but not surviving being frozen (1 to 5)
H3: hardy in coastal and relatively mild parts of the UK (-5 to 1)
H4: hardy through most of the UK (-10 to -5)
H5: hardy in most places throughout the UK even in severe winters (-15 to -10)
H6: hardy in all of UK and northern Europe (-20 to -15)
H7: hardy in the severest European continental climates (< -20): H4

Colour & Scent

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Hypericaceae
Native to GB/Ireland: No
Foliage: Deciduous
Habit: Bushy
Potentially harmful: Fruit are ornamental - not to be eaten. Wear gloves and other protective equipment when handling. Pets: Fruit are ornamental - not to be eaten - see the HTA guide to potentially harmful plants for further information and useful contact numbers
Genus: Hypericum can be annuals, perennials, shrubs or trees, evergreen or deciduous, with usually paired leaves and showy yellow flowers with prominent stamens, followed by capsules, occasionally berry-like
Name Status: Accepted

How to Grow

Cultivation

Grows well in moderately fertile, moist but well-drained soil full sun. It will tolerate partial shade. Ideal for a rock garden.

Propagation

Propagate by softwood cutting or semi-ripe cuttings from late spring to early summer.

Suggested planting locations and garden types

Cottage and informal garden
Gravel garden
Patio and container plants
Rock garden
City and courtyard gardens

Pruning

Pruning group 1 or pruning group 6

Pests

Generally pest-free

Diseases

May be susceptible to a rust and honey fungus (rarely)