Friday, 11 January 2013

The great Veronica hunt, part 1.

Veronica anagallis-aquatica.
My main current work task is a Flora treatment of the genus Veronica, which has 17–18 naturalised species and over 120 native ones.  We've revised the native species in a series of monographs of the previously-recognised New Zealand genera (Hebe & Leonohebe, Parahebe, Heliohebe, Chionohebe; and here's why I treat them all as Veronica now) and the naturalised ones were treated by Bill Sykes in the 1988 Flora.  Since then a couple of additional species have been found in the wild, like V. peregrina at Kakariki, near Bulls (that's a locality, not a commensal association).

So yesterday when I delivered some plants of the native species V. planopetiolata and V. colostylis to Massey University in Palmerston North, I took advantage of the trip to do some field work to try to get photographs for the new Flora.  I targeted V. peregrina because it's only known at the one site.  But first I went to look in a drain east of the Massey campus where V. anagallis-aquatica had been very common when recently collected.  There was none there at all, and this demonstrates a common problem with weeds: their habitat changes all the time.  Maybe the drain was drier this year, maybe the roadside had been sprayed with herbicides, or maybe other plants had crowded the Veronica out.  There was a healthy population of Parentucellia viscosa, a non-parasitic member of the Orobanchaceae.
Parentucellia viscosa flower, near Massey University, Palmerston North.
So I moved on to Kakariki, where fortunately I had excellent directions for the locality where Veronica peregrina had been found, in silty hollows alongside the Main Trunk Railway line.  To cut a long story short, I spent at least an hour there in the hot sun, sweat running down my face from under my hat, and found nothing.  But there were some interesting little plants among the dried up moss.

Linum trigynum, Kakariki.
This little yellow flax was one.  New Zealanders will balk at hearing this called flax, but our large monocot Phormium is called flax only because of its linen-like fibres, and true flax is the genus Linum.

Traveller's joy, Clematis vitalba.
There was a small patch of old man's beard or traveller's joy in flower, and again here's a common name question.  Old man's beard also applies to the lichen Usnea, but traveller's joy seems too benign a name for this nasty invasive climber.

Two possible reasons for the absence of Veronica peregrina spring to mind.  It could be that it's an ephemeral weed that comes up in the spring when these hollows are filled with water and dies off quickly as they dry out in early summer.  Alternatively the plant might have flourished here briefly and then died out again, just like V. anagallis-aquatica at the Massey site.  Its discoverer tells me he hasn't seen it in recent visits to the site, so the latter seems the more likely explanation, but I think I need to go back there next spring for another look (hopefully with a spot of lunch at Macfarlane's Cafe in nearby Feilding).

It seems odd that a new weed for the country could appear and flourish for a while in a tiny isolated patch alongside the railway and not be found anywhere else.  So I thought it would be smart to look down by the Rangitikei River nearby, where damper soil patches might be found.

Equisetum arvense between the bridges at Kakariki.
The first plant I saw there was a vigorous and extensive population of horsetail, Equisetum.  This odd fern genus has a world-wide native distribution except New Zealand and Australia and it's an unwelcome invasive introduction.  I know, it doesn't look like a fern, but it does belong in a large grouping that includes the "true" ferns, which are distinctive because of their pinnate spirally-unfolding leaves and thin-walled spore capsules.
Equisetum arvense, Kakariki.
The leaves are high in silica, so it used to be used as an abrasive, e.g., for scouring pots.  A friend tells me the violin-makers at Cremona use it to gently abrade the lacquer layers in violins between coats.

Veronica, Rangitikei river bed at Kakariki.
Across the river I found the wet silt I was looking for, among stones on the river bed.  And here was a Veronica, not V. peregrina, but one of the aquatic species that I hadn't photographed before.  Within the small population there were plants with pink flowers and plants with mauve flowers.  Flower colour is said to distinguish V. catenata (pink) from V. anagallis-aquatica (blue).  This looked to me like a polymorphic single population, but I guess there could be two species growing together.

Mauve and pink flowered plants of Veronica anagallis-aquatica, Rangitikei River at Kakariki.
There were other differences.  Some of the mauve-flowered plants had glandular cilia on the capsules; the pink one had glabrous capsules.  The Flora says glandular-ciliate for V. anagallis-aquatica, ciliate for V. catenata.  No plants had the spreading pedicels said to be characteristic of V. catenata.  I'm going to go with V. anagallis-aquatica for all these plants for now, but to use different collection numbers for the pink and mauve ones, so they can be separated later if need be.

It's going to be a challenge getting all 17–18 introduced species.  Many are quite local, and likely not to be present at sites where they have been collected in the past.  I've already done the three common local species: V. arvensis, V. persica, and V. serpyllifolia, and now I've added V. anagallis-aquatica.  I'd be happy to hear of sites where the others can be collected, so I can add more posts to this series on the Great Veronica Hunt.

No comments:

Post a Comment