Alcea rosea 'Polarstar' (Spotlight Series)

RHS Plant Profile
hollyhock 'Polarstar'

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A short-lived perennial with lobed rounded leaves and long, erect pyramids of open funnel-shaped white single flowers with a yellow eye in summer.

Position

Full sun

Soil Types

Chalk, Loam, Sand

Max Height

1.5-2.5 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity
1 year
Max Spread
0.1-0.5 metres
Max Height
1.5-2.5 metres

Growing Conditions

Chalk Loam Sand
Moisture
Well–drained
pH
Acid or Alkaline or Neutral

Position

Full sun
Aspect
South–facing
Exposure
Exposed or 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)
H5

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Malvaceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Columnar upright
Genus
Alcea are robust biennials or short-lived perennials with showy funnel-shaped flowers borne in tall, erect racemes in summer
Name Status
Accepted

How to Grow

Cultivation

Thrives in well-drained, moderately fertile soil in full sun. May need support on exposed sites, see staking perennials

Propagation

Propagate by seed, sown in gentle heat in midwinter, or in situ in spring

Suggested planting locations and garden types

  • Architectural
  • City and courtyard gardens
  • Cottage and informal garden
  • Low Maintenance
  • Wall side borders

Pruning

Cut back dead foliage after flowering, or pull out and discard - growing as annuals or biennials can help limit the spread of rust

Pests

May be susceptible to cutworms and slugs on young growth, and to capsid bugs, aphids and mallow flea beetles

Diseases

May be susceptible to hollyhock rust