Phlox '21st Century White'

RHS Plant Profile
phlox '21st Century White'

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An upright annual with small, lance-shaped dark-green leaves and large clusters of white flowers with a subtle yellow eye for a long period of time in summer. Has long branching, wiry stems, very suited as a cut flower

Position

Full sun, Partial shade

Soil Types

Chalk, Loam, Sand

Max Height

0.5-1 metres

Max Spread

0.5-1 metres

Size

Time to Maturity
1–2 years
Max Spread
0.5-1 metres
Max Height
0.5-1 metres

Growing Conditions

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

Position

Full sun Partial shade
Aspect
West–facing or 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)
H3

Colour & Scent

Fragrance Flower
Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Polemoniaceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Columnar upright
Genus
Phlox may be evergreen or herbaceous, mat-forming or erect perennials or shrubs, with simple leaves and salver-shaped flowers in terminal clusters
Name Status
Accepted

How to Grow

Cultivation

Grow in fertile, moist soil in full sun or partial shade. See phlox cultivation for further advice

Propagation

Propagate by seed in spring

Suggested planting locations and garden types

  • Cottage and informal garden
  • City and courtyard gardens
  • Patio and container plants
  • Flower borders and beds

Pruning

Cut back after flowering

Pests

May be susceptible to stem and bulb eelworm

Diseases

May be susceptible to powdery mildews and leaf spot