Phlox paniculata 'Blue Boy'

RHS Plant Profile
perennial phlox 'Blue Boy'

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perennial phlox 'Blue Boy' RHS
perennial phlox 'Blue Boy' Dorling Kindersley Ltd

Synonyms

Phlox paniculata 'Boy Blue'

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Herbaceous Perennial
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A strong-growing herbaceous perennial 90-120cm high with green lance-shaped leaves and large clusters of scented, mauve-blue flowers, with darker purple and white eyes, from summer to early autumn

Position

Full sun

Soil Types

Clay, Loam

Max Height

0.5-1 metres

Max Spread

0.5-1 metres

Size

Time to Maturity
2–5 years
Max Spread
0.5-1 metres
Max Height
0.5-1 metres

Growing Conditions

Clay Loam
Moisture
Moist but well–drained
pH
Acid or Alkaline or Neutral

Position

Full sun
Aspect
West–facing or South–facing or East–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)
H7

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
Clump forming
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 division in autumn or spring, by basal cuttings in spring or by root cuttings from early autumn to spring; root cuttings are the best method to ensure healthy plants

Suggested planting locations and garden types

  • City and courtyard gardens
  • Cottage and informal garden
  • Prairie planting
  • Wildlife gardens
  • Cut flowers
  • Flower borders and beds
  • Wall side borders

Pruning

Deadhead to prolong flowering; cut down to the base in late autumn and remove the cut stems, to reduce the risk of eelworm and mildew the following year

Pests

Generally pest-free but may be susceptible to slugs, snails, aphids, and Phlox stem eelworm

Diseases

Generally disease-free but may be susceptible to crown gall, leafy gall, fungal leaf spot and Verticillium wilt; said to have good resistance to powdery mildews