Cyathea medullaris Black Tree Fern or Mamaku Native to: New Zealand; Fiji; Polynesia Size: trunk grows to 20-200 inches; fronds grow to 80-120 inches Climate: temperate; subtropical Grow in: Protected location with good supply of water Given the right location, this tree will grow to be a hearty, adaptable source of shade. Its large head covering has black scales and lacy fronds. This fast growing tree will develop a huge crown in a comparatively short time.