Alsophila smithii

RHS Plant Profile
soft tree fern

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Synonyms

Cyathea smithii

Ferns
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A slow-growing tree fern with an upright trunk covered in chestnut-coloured scales eventually reaching 5-8m tall. Fronds to 2.5m long are held horizontally from the crown and made up of soft, delicate leaflets, the longest reaching to 50cm, dark green above and paler green on the undersides

Position

Partial shade

Soil Types

Loam, Sand

Max Height

4-8 metres

Max Spread

2.5-4 metres

Size

Time to Maturity
20–50 years
Max Spread
2.5-4 metres
Max Height
4-8 metres

Growing Conditions

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

Position

Partial shade
Aspect
North–facing or West–facing or East–facing
Exposure
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

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Cyatheaceae
Native to GB/Ireland
No
Foliage
Evergreen
Habit
Columnar upright
Genus
A genus of tree ferns, native to the tropics and subtropics, with upright stems and large, dark green fronds on top of the stems
Name Status
Correct
Plant Range
New Zealand

How to Grow

Cultivation

In areas prone to frost, grow in a container under glass with a minimum winter temperature of 10°C. The plant may be placed outside during the summer in a sheltered and partially-shaded spot. It requires a moist but well-drained, humus-rich soil; in hot, dry summers water the stem as well as the soil, but avoid watering the crown in winter. Apply liquid fertiliser monthly during the growing season. Will grow without winter protection only in milder areas

Propagation

Propagate by sowing spores as soon as ripe

Suggested planting locations and garden types

  • Architectural
  • City and courtyard gardens
  • Coastal
  • Flower borders and beds

Pruning

Dead or damaged fronds may be removed as necessary

Pests

Generally pest-free

Diseases

Generally disease-free