Phlox paniculata 'Roberta'

RHS Plant Profile
perennial phlox 'Roberta'

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An upright, clump-forming deciduous perennial with glossy dark green leaves. Fragranced, red-purple flowers are produced in summer and autumn.

Position

Full sun, Partial shade

Soil Types

Chalk, Loam, Clay

Max Height

0.5-1 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity
2–5 years
Max Spread
0.1-0.5 metres
Max Height
0.5-1 metres

Growing Conditions

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

Position

Full sun Partial shade
Aspect
East–facing or South–facing or West–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
Unresolved

How to Grow

Cultivation

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

Propagation

Propagate by basal cuttings in spring, or take root cuttings in early autumn or winter

Suggested planting locations and garden types

  • City and courtyard gardens
  • Cottage and informal garden
  • Wildlife gardens
  • Flower borders and beds
  • Wall side borders

Pruning

Prune back to the base in late autumn. Deadhead regulary to prolong flowering

Pests

May be susceptible to stem eeelworms

Diseases

May be susceptible to leaf spot and leaf gall. Good mildew resistance