Juglans nigra (F)

RHS Plant Profile
black walnut

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black walnut RHS 1999

Other common names

American walnut

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Trees
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A vigorous, large, deciduous, broad-crowned tree with large pinnate leaves composed of 15-21 lanceolate leaflets, with 10cm long male catkins and insignificant female flowers followed by globose green fruits, 5cm wide

Position

Full sun

Soil Types

Chalk, Clay, Loam, Sand

Max Height

Higher than 12 metres

Max Spread

wider than 8 metres

Size

Time to Maturity
more than 50 years
Max Spread
wider than 8 metres
Max Height
Higher than 12 metres

Growing Conditions

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

Position

Full sun
Aspect
South–facing or West–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)
H6

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Juglandaceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Bushy
Genus
Juglans are deciduous trees with pinnate leaves, and inconspicuous flowers in catkins followed by usually edible nuts
Name Status
Correct
Horticultural Group

Horticultural Classification Codes

Horticultural Classification Codes are often given to genera which have a large number of species or cultivars. They are used to categorise cultivated plants based on specific, shared characteristics such as shape, colour, size or flowering time, and can be displayed as letters or numbers

For example:
Dahlia ‘Sunset Kate (Sin) = Single flower
Rosa ‘Marigold’ (HT) = Hybrid Tea

Produces walnuts
Plant Range
E USA

How to Grow

Cultivation

Grow as a specimen tree in any well-drained or moist but well-drained soil in full sun

Propagation

Propagate by seed or grafting

Suggested planting locations and garden types

  • Low Maintenance

Pruning

Pruning group 1

Pests

May be susceptible to aphids and walnut blister mite

Diseases

May be susceptible to walnut leaf spot, walnut leaf blotch, honey fungus and coral spot