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ShrubsAlpine Rockery

Lithodora zahnii

Zahn's gromwell

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

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Ultimate height

0.1–0.5 metres

Time to ultimate height

5–10 years

Ultimate spread

0.1–0.5 metres

Chalk

Loam

Sand

Moisture

Well–drained

pH

Alkaline, Neutral

	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

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)

Botanical details

Family: Boraginaceae
Native to the UK: No
Foliage: Evergreen
Habit: Bushy
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

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