Sphaeropteris medullaris

RHS Plant Profile
black tree fern

Other common names

black-stemmed tree fern, gray tree fern, mamaku, sago fern

Synonyms

Cyathea medullaris
Cyathea cumingii

Award of Garden Merit
Ferns

An evergreen, upright tree fern eventually reaching heights of 7-16m. Its slender black trunk bears fronds to 5m long arching up from the crown and made up of small, oblong, glossy leaflets with scaly undersides and spines along the margins

Position

Partial shade

Soil Types

Loam, Sand

Max Height

Higher than 12 metres

Max Spread

wider than 8 metres

Size

Time to Maturity
20–50 years
Max Spread
wider than 8 metres
Max Height
Higher than 12 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
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-fern with tall, single scaley stems and large yellow-brown to purple fronds at the top of these stems
Name Status
Correct
Plant Range
New Zealand to S Pacific

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. See how to grow tender ferns outdoors for further advice

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