Tuesday, 30 October 2012

Wednesday wildflower: Spanish heather

Erica lusitanica is quite invasive, and it seems to do particularly well on clay soils in Wellington.  The epithet lusitanica strictly refers to Portugal, but I guess the species is more widespread than that, so its common name isn't inaccurate.
Erica lusitanica, Messines Road, Karori, Wellington.
They're straggly and untidy plants, yet up close, Erica lusitanica has a pretty hanging flower that starts out pink and fades to white.
Flowers of Spanish heather.

Weed or wildflower, it does at least provide a habitat for the native bag moth.
Bag moth larva, on Erica lusitanica.

Erica is, of course, in the family Ericaceae.  Also in that family: Rhododendron, blueberries, and the native Dracophyllum.

A cultivated Rhododendron, Wellington.
Dracophyllum strictum, cultivated
Dracophyllum scoparium, Campbell Island.

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.

Tuesday, 23 October 2012

Wednesday wildflower: chickweed.

Last week’s wildflower was the annual mouse-ear chickweed (Cerastium glomeratum).  This week’s wildflower is a chickweed that’s not hairy, or at least barely hairy.  Chickweed is also an edible weed.
A thicket of chickweed, Karori.
Like mouse-ear chickweed, Stellaria media has five divided petals, but these are deeply divided so that the flower seems to have ten simple petals.  There are three stigmas instead of five, a clue that the ovary is made up of only three carpels, but in this family there aren’t any partitions inside the ovary.  There are usually 3–5 stamens, but can be as many as 10.  The single line of hairs along the pedicel (flower stalk, below) is a distinctive feature.
Chickweed, Karori.  Both leaf surfaces (upper on left), a flower, and a young fruit.
This is the commonest of the three introduced chickweeds (the others are S. alsine and S. graminea).  There are also five native chickweeds: S. decipiens, S. elatinoides (probably extinct), S. gracilenta, S. parviflora, and S. roughii.
Stellaria decipiens, Garden Stream, Campbell Island
S. decipiens is hard to distinguish reliably from S. parviflora, but is often fleshy.  It’s confined to the subantarctic islands.  This one has no petals, which sometimes happens in S. parviflora too.
Stellaria gracilenta, Canterbury.
S. gracilenta is a common plant in tussock grasslands in North and South Islands.

Stellaria parviflora, Mt Herbert, Banks Peninsula.
S. parviflora is a delicate herb of the forest floor, and common throughout New Zealand.  In the flower above, the petals are the same length as the sepals, although my description in Flora of New Zealand (Webb et al., 1988) says "petals much < sepals or 0".

Stellaria roughii, Cragieburn Range, Canterbury.
S. roughii is a scree-adapted plant.  It has grey fleshy leaves like other unrelated plants in this harsh habitat.
We don't know yet whether these native Stellarias are all related closely to each other and derived from a single introduction, or whether they represent multiple introductions.


Webb, C.J.; Sykes, W.R.; Garnock-Jones, P.J. 1988.  Flora of New Zealand Vol. 4.  DSIR, Christchurch.

Tuesday, 16 October 2012

Wednesday wildflower: annual mouse-ear chickweed

There's mouse-ear (Myosotis) and there's mouse-ear chickweed (Cerastium).  True chickweeds are Stellaria, which isn't particularly hairy, but the mouse-ear chickweeds are furry like Myosotis, or like a mouse's ear.  They're not related to Myosotis however, in spite of their superficially similar leaves.
Cerastium glomeratum, Karori, Wellington.
This one is very common.  It's the annual mouse-ear chickweed, C. glomeratum.  Its leaves have green edges (some of the other species have scarious—thin, dry, almost translucent—edges to at least the uppermost leaves) and hairs overtop the apex of the sepals.  The flower stalks are shorter than the flowers and fruits, hence the name glomeratum, which refers to the rounded cluster of flowers.  

We have five species naturalised in New Zealand.  C. arvense (below) has larger flowers, and is often established on limestone.
Cerastium arvense, Cass, Canterbury.

Tuesday, 9 October 2012

Wednesday wildflower: forget-me-not.

Garden forget-me-not, Myosotis sylvatica, Karori.

We have about half a dozen introduced species of Myosotis in New Zealand.  This one, M. sylvatica, is a common garden ornamental, and has probably escaped into the wild many times from gardens.  Although the flowers are blue, white or pink mutants arise occasionally and these have been selected and propagated by growers.  Sometimes they escape into the wild too.  It’s a bit of a clue as to how the native species came to be mostly white-flowered.
Blue and white forget-me-not flowers from separate wild plants in Glenmore St, Wellington, perhaps escapes from the nearby Botanic Gardens, where they are grown as bedding annuals.
The English name for Myosotis is forget-me-not, although the scientific name translates as mouse-ear, a reference to the shape and furriness of the leaves.  
Myosotis sylvatica leaf
Like Veronica, this genus has two main centres of diversity: Eurasia and New Zealand.  And just as in Veronica, not only do we have a large number of species, but they are very diverse in their growth forms, flower colours, flower biology, and habitats, yet show very little variation in the DNA sequences that have been studied so far.  In both genera, we probably have more variability of form in the New Zealand species than in the rest of the genus put together, but only a small proportion of the genetic variability.  That’s in keeping with the idea that these groups have arrived here quite recently (in geological terms), and that they found a lot of unfilled niches here.  Natural selection took over and populations became adapted to different habitats and pollinators so rapidly that it’s difficult to accurately trace their evolutionary history from the DNA record.  The botanists at Te Papa are studying Myosotis, and their research will document its biodiversity, aiding conservation efforts.
Myosotis capitata, SW Cape, Auckland Island.
Only two native forget-me-nots have blue flowers; the rest are mostly white with some yellow.  Both our blue forget-me-nots grow in the subantarctic islands—Auckland Islands and Campbell Island—where plants in other groups also have striking coloured flowers.  It’s easy to understand why native Myosotis and Veronica don’t generally have blue flowers in New Zealand: we have no native long-tongued social bees that are the specialist pollinators of many blue flowers in Europe.  So any chance mutants with white flowers probably reproduced better here that they would in Europe, and perhaps better than their blue-flowered relatives.  But it’s much harder to explain the presence of coloured flowers in the subantarctic, where not only are there no long-tongued social bees, but very few other flying insects.
Myosotis antarctica, Col-Lyall Saddle, Campbell Island, with Epilobium.
M. antarctica (above) is part of the rather diverse M. pygmea complex, recently split into several species and all these have very small flowers.  Some others are below:
Myosotis drucei, Black Birch Range, Marlborough, with Stellaria gracilenta.

A plant in the M. pygmaea complex, Mt Herbert, Banks Peninsula.

A plant in the M. pygmea complex, Southland coast at Waituna Lagoon.

My final native forget-me-not is M. saxosa, below.
Myosotis saxosa, Maungaharuru Range, Hawkes Bay.

Tuesday, 2 October 2012

Wednesday wildflower: Veronica persica

I've written a few posts about native New Zealand species of Veronica, many of which are hebes.  Lately I've been looking more closely at the introduced species.  There are 16 of these if you regard V. plebeia as native.  One of the commonest is V. persica.
Veronica persica, Kaitoke, Wellington, New Zealand.
It is a common weed in gardens and roadsides.  There are two other common species in similar habitats: V. arvensis and V. serpyllifolia, but these both have much smaller flowers.
Veronica persica flower, Karori, Wellington, New Zealand (scale 1mm)
The flowers have been reported to be pollinated by syrphid flies (hover flies).  A syrphid will fly in to the flower rubbing off pollen from its abdomen onto the protruding stigma.  To hold on while it's feeding, it grasps the bases of the stamen filaments, but these are very narrow at the base and bend like a hinge.  This pulls the anthers into contact with the fly's abdomen, dusting off pollen there.
The native Veronica lilliputiana has creeping stems, tiny greyish leaves, and blue flowers with nectar guides.
Very few native Veronica have such bright blue flowers.  Mostly they're white, sometimes with a touch of blue or mauve.  But V. benthamii in the subantarctic Auckland & Campbell Islands is a good veronica blue, and the tiny creeping V. lilliputiana is also blue, but paler.  A similar thing happens in the forget-me-nots, Myosotis, where most native species have white or yellow flowers, yet two in the subantarctic islands are blue, M. capitata and M. antarctica.  These introduced Veronica also have nectar guides, coloured lines on the corolla lobes, which are thought to attract and guide pollinators.  Again, these are not common in native Veronica, but the speedwell hebe group (about half the former genus Parahebe, e.g., V. lanceolata) have them.  V. lilliputiana has both blue flowers and nectar guides.
Veronica benthamii (Bentham's hebe), SW Cape, Auckland Island.