Vernonia noveboracensis

RHS Plant Profile
New York ironweed

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New York ironweed Dorling Kindersley Ltd

Other common names

New York flat tops

Herbaceous Perennial
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A tall, herbaceous perennial to 2m with stiff, upright stems carrying narrow, pointed leaves and topped with open, branched clusters of purple, thistle-like flowers in late summer and early autumn

Position

Full sun, Partial shade

Soil Types

Chalk, Clay, Loam

Max Height

1.5-2.5 metres

Max Spread

0.5-1 metres

Size

Time to Maturity
2–5 years
Max Spread
0.5-1 metres
Max Height
1.5-2.5 metres

Growing Conditions

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

Position

Full sun Partial shade
Aspect
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

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Asteraceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Columnar upright
Genus
Vernonia are annuals, perennials, climbers, sub-shrubs, shrubs and trees, though only the perennials are in cultivation. They have upright stems, simple, stalkless leaves and flat branched heads of tubular purple or reddish pink, occasionally white, flowers
Name Status
Correct
Plant Range
E USA & New Mexico

How to Grow

Cultivation

Grow in any light, moist soil in full sun or partial shade

Propagation

Propagate by seed or division

Suggested planting locations and garden types

  • Cottage and informal garden
  • Prairie planting
  • Flower borders and beds

Pruning

Deadhead regularly to prolong flowering

Pests

May be susceptible to slugs

Diseases

Generally disease-free