Friday, 26 October 2012

Another Pittosporum

I never cease to be impressed by the flower diversity within New Zealand Pittosporum.  This week I had the chance to photograph P. obcordatum.  The flowers are tiny, and very different in general appearance from the others I've seen.  Like others in the genus, they're sweetly scented, but the scent is rather faint, at least to my nose, and seems strongest at night.
Pittosporum obcordatum
P. obcordatum, the heart-leaved kōhūhū, is quite rare; so it was great news recently that a small population has just been rediscovered on Banks Peninsula.  (Unfortunately the linked article describes it hard to find because it's a cryptic species, but that's not what cryptic species means.  A cryptic species is one that's very hard to distinguish from another related (usually sister) species, where breeding barriers have arisen without morphological changes.  In the case of P. obcordatum, it's the plants that are cryptic, not the species.  Although it's true that other divaricating shrubs can look superficially like P. obcordatum, they have plenty of differences to distinguish them.)

This plant, cultivated on campus at Victoria University, is a female.

Pittosporum obcordatum flowers
For comparison, here are some other pittosporums.

Pittosporum eugenioides.
P. eugenioides is dioecious (has separate male and female plants), and has large clusters of pale yellow flowers.  The males and female flowers are quite different:
Pittosporum eugenioides flowers: female above; male below.
There's a group of species with dark red, almost black, flowers, also sweet-scented at night, like this P. tenuifolium.
Pittosporum tenuifolium flower.
P. tenuifolium is gynodioecious (separate male and female plants, but the males can set some seed even though most of their reproduction is through their pollen).  This one appears to be a male.

The two species I've already illustrated here have narrow pointed petals, and both grow as epiphytes (plants that grow on other plants, but are not parasitic on them).  These are P. kirkii and P. cornifolium.

Finally, a scan of an old slide of P. dallii.  Its flowers are similar to those of P. eugenioides, but its toothed leaves are very different.
Pittosporum dallii.

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