Chrysanthemum 'Sea Urchin' (21f)

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chrysanthemum 'Sea Urchin'

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chrysanthemum 'Sea Urchin' RHS
chrysanthemum 'Sea Urchin' RHS

Synonyms

Dendranthema 'Sea Urchin'

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Herbaceous Perennial
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'Sea Urchin' is a relatively low-growing cultivar, to 55cm in height. Flowers in mid autumn with yellow quilled florets

Position

Full sun

Soil Types

Loam

Max Height

0.1-0.5 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity
1 year
Max Spread
0.1-0.5 metres
Max Height
0.1-0.5 metres

Growing Conditions

Loam
Moisture
Moist but well–drained
pH
Neutral

Position

Full sun
Aspect
South–facing or East–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)
H3

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Asteraceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Bushy
Potentially harmful
Skin allergen. Wear gloves and other protective equipment when handling
Genus
Chrysanthemum are erect woody-based perennials with aromatic, pinnately lobed leaves and flowerheads of diverse form, from late summer to late autumn
Name Status
Accepted
Horticultural Group

Horticultural Classification Codes

Horticultural Classification Codes are often given to genera which have a large number of species or cultivars. They are used to categorise cultivated plants based on specific, shared characteristics such as shape, colour, size or flowering time, and can be displayed as letters or numbers

For example:
Dahlia ‘Sunset Kate (Sin) = Single flower
Rosa ‘Marigold’ (HT) = Hybrid Tea

Korean chrysanthemums (21f) are perennials with a range of flower types, including Spider, with long, narrow, pendent ray florets; Spoon, with tubular rays opening to a spoon-shape at the tip; and Quill, with slender, tubular rays oblique at the tip

How to Grow

Cultivation

Korean chrysanthemums are borderline hardy. Overwinter more tender cultivars in a cold frame. Needs a sunny site with moderately fertile, well-draining soil. See chrysanthemum cultivation

Propagation

May be propagated by division in late spring or by cuttings

Suggested planting locations and garden types

  • Flower borders and beds

Pruning

Cut down after flowering

Pests

May be susceptible to chrysanthemum leaf miner, glasshouse whitefly and aphids

Diseases

May be susceptible to glasshouse grey moulds, powdery mildews and chrysanthemum white rust