Ceanothus 'Cynthia Postan'

RHS Plant Profile

Californian lilac 'Cynthia Postan'

RHS

Shrubs

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A dense, rounded, evergreen shrub to 2.5m tall with glossy, dark green leaves to 4cm long, and rich blue flowers profusely borne in dense clusters in late spring and early summer

Position

Full sun

Soil Types

Loam, Sand

Max Height

1.5-2.5 metres

Max Spread

1.5-2.5 metres

Size

Time to Maturity: 2–5 years
Max Spread: 1.5-2.5 metres
Max Height: 1.5-2.5 metres

Growing Conditions

Loam Sand

Moisture: Well–drained
pH: Acid or Alkaline or Neutral

Position

Full sun

Aspect: South–facing or West–facing
Exposure: 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
Drought Resistance: Yes

Colour & Scent

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Rhamnaceae
Native to GB/Ireland: No
Foliage: Evergreen
Habit: Bushy
Genus: Ceanothus can be evergreen or deciduous shrubs or small trees, with simple leaves and small blue, pink or white flowers in profuse axillary or terminal clusters. They are fast-growing but may be short-lived
Name Status: Accepted

How to Grow

Cultivation

Grow in fertile, well-drained soil in full sun with shelter from strong, cold winds. Lime tolerant but may become chlorotic on shallow chalk soils. See ceanothus cultivation

Propagation

Root semi-ripe cuttings in mid- to late summer

Suggested planting locations and garden types

Gravel garden
City and courtyard gardens
Coastal
Cottage and informal garden
Mediterranean climate plants
Wildlife gardens
Wall side borders
Flower borders and beds

Pruning

Pruning group 8 after flowering or pruning group 13 if wall trained

Pests

May be susceptible to scale insects

Diseases

May be susceptible to honey fungus