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Herbaceous Perennial

Veronicastrum sibiricum 'Kobaltkaars'

Culver's root 'Kobaltkaars'

An upright, clump-forming, rhizomatous perennial to 1.4m, with large, broadly linear green leaves arranged in whorls around the stems. Tall, thick spikes of lilac-blue flowers appear from June to August

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Plant nurseries
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Ultimate height

1–1.5 metres

Time to ultimate height

2–5 years

Ultimate spread

0.1–0.5 metres

Chalk

Clay

Loam

Sand

Moisture

Moist but well–drained

pH

Acid, Alkaline, Neutral

	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Full sun
Partial shade

Aspect

East–facing or 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)

Botanical details

Family: Plantaginaceae
Native to GB / Ireland: No
Foliage: Deciduous
Habit: Clump forming
Genus: Veronicastrum are tall herbaceous perennials with erect stems bearing narrow leaves in whorls, and long terminal racemes of small flowers in summer
Name status: Unresolved

How to grow

Cultivation

Grow in moderately fertile, humus-rich, moist soil in sun or partial shade

Propagation

Propagate by by sowing seed in pots in a cold frame in autumn, or by division in spring

Suggested planting locations and garden types

Cottage and informal garden
Flower borders and beds

Pruning

Cut back old stems in early spring

Pests

May be susceptible to aphids

Diseases

May be susceptible to leaf spot, downy mildews and powdery mildews

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