Cyathea medullaris

"Mamaku"
"Black Tree Fern"

This very large treefern is native to New Zealand, Fiji, and Polynesia.  In New Zealand it is possibly the most common tree fern, and it is found growing in a large range of microclimates and situations throughout the island.  It is a rapid grower and makes a very imposing specimen even in less than perfect conditions.  Unlike C. dealbata and C. smithii, it generally found growing in open places with full exposure to wind and sun.  Although relatively few fronds remain on the crown at once, they can reach over 12' long on vigorous young plants.  Its large size and black shiny leaf bases make it a most spectacular plant in cultivation.  This species is not yet common in gardens, though there are a few in the British Isles, including one that has already spent a few winters outdoors in Ireland.

Although it is very adaptable, it seems to be only slightly hardier than C. cooperi, and its massive size makes it a formidable challenge to protect from cold.  In addition to this, its preference for open places limits the number of positions in a garden or landscape available to site it that are relatively sheltered from cold.  It ought to be able to withstand temperatures down to about 25°F before the cold would begin to do serious damage.  Some high elevation provenances may be a couple degrees hardier than this.  The ideal situation for it is where its fronds get full sun, but the trunk can remain moist.

Cyathea medullaris in habitat in New Zealand, demonstrating its preference for open sunny locations.  Photo courtesy of Peter Richardson.

Cyathea medullaris in habitat in New Zealand.  Photo courtesy of Peter Richardson.

Cyathea medullaris at a hotel in New Zealand.  It certainly makes quite a dramatic landcape plant.  Photo courtesy of Peter Richardson.

Cyathea medullaris at Oasis Designs Nursery, Essex, UK.  Photo courtesy of Paul Spracklin.

Cyathea medullaris silhouette in New Zealand.  Photo courtesy of Ralph Booth.

Cyathea medullaris with Queen Charlotte Sound in the background.  Photo courtesy of Ralph Booth.

A slab of trunk of Cyathea medullaris.  Treefern trunks are handy for growing epiphytic ferns and other epiphytes on.  Photo courtesy of Ralph Booth.

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