Lithodora zahnii

RHS Plant Profile
Zahn's gromwell

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An upright, many-branched, evergreen shrub, to 30cm tall, with narrow, leathery, dark grey-green leaves. Small terminal clusters of blue or white flowers are produced all summer and sporadically in autumn

Position

Full sun

Soil Types

Chalk, Loam, Sand

Max Height

0.1-0.5 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity
5–10 years
Max Spread
0.1-0.5 metres
Max Height
0.1-0.5 metres

Growing Conditions

Chalk Loam Sand
Moisture
Well–drained
pH
Alkaline or Neutral

Position

Full sun
Aspect
West–facing or South–facing
Exposure
Exposed
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
Boraginaceae
Native to GB/Ireland
No
Foliage
Evergreen
Habit
Bushy
Genus
Lithodora are evergreen shrubs or sub-shrubs, with 5-lobed blue or white flowers in early spring to summer
Name Status
Correct
Plant Range
S Greece

How to Grow

Cultivation

Grow in well-drained, preferably alkaline to neutral soil in full sun

Propagation

Propagate by semi-ripe cuttings in summer

Suggested planting locations and garden types

  • Rock garden
  • City and courtyard gardens
  • Coastal
  • Cottage and informal garden
  • Gravel garden
  • Patio and container plants
  • Banks and slopes
  • Flower borders and beds

Pruning

Pruning group 8; or pruning group 10 after flowering

Pests

Generally pest-free

Diseases

May be susceptible to honey fungus in gardens where it is present but insufficient data to determine degree of susceptibility