Two of them, Pennantia baylisiana and Tecomanthe speciosa, must be the world's equal rarest plants, because both are known from only single individuals on the Three Kings Islands. You could argue that P. baylisiana is even rarer because the only plant is a female; however somehow it occasionally produces fruits which are a prospect for its reintroduction in the wild. Both are well established in New Zealand gardens.
|Elingamita johnsonii in my garden.|
The plant in my garden is a male, and I've had it about 20 years. For some of that time it lived in a pot in my office, where it suffered badly from scale insects. After a while I took a risk and planted it out in the garden, and it hasn't looked back. Now I'm having to build a dog-leg in a new retaining wall, to avoid burying its roots.
|Elingamita johnsonii, male flowers starting to open|
|Elingamita johnsonii, male flowers.|
|Elingamita johnsonii, a male flower soon after opening|
|Elingamita johnsonii. At a later stage, when the filaments begin to elongate (right) and the anthers release their pollen (left).|
|Myrsine australis female flower. Note the expanded stigma (out of focus in the centre).|
|Myrsine australis male flower. Note that the four petals are shortly joined into a tube|
How did Elingamita come by its name? It's named after the S.S. Elingamite, which ran aground in 1902 on West Island in the Three Kings, with the loss of forty-five lives. One other native plant I know of commemorates a shipwreck: Lepidium naufragorum, a coastal cress. The name refers to cast-aways, nine (correction 16 Feb 2013: the accounts I've linked to say ten) sealers who were dropped on the Open Bay Islands in 1810. Their ship was never seen again, but they were rescued after 4 years of hardship.