Christmas Bells

Christmas Bells
Christmas Bells - Blandfordia nobilis

Sunday, April 19, 2009

Tiny Greenhoods and a Terminal Wattle

Yesterday I went to Manning Lookout, a Sandstone bluff overlooking the Kangaroo Valley, just a few Kilometres from Robertson. This Lookout is near Fitzroy Falls, but it overlooks the centre of Kangaroo River valley (and the village of Kangaroo Valley). By contrast, the lookouts at nearby Fitzroy Falls mostly look into the giant valley of the Shoalhaven River - with a southwesterly perspective. It is all part of the same Shoalhaven valley system, just that the Kangaroo River starts above Carrington Falls, north-east of Kangaroo Valley village, and it runs south-west until it meets the Shoalhaven River system. These days, the junction of these rivers is within Tallowa Dam.

Manning Lookout is one of my favourite places, locally, both for scenic attractiveness, and also for plants, fungi, birds and for gentle bushwalking. But yesterday, the main point of interest was the local autumn-flowering plants. There were many Banksias just coming into season, and I shall deal with them in the coming days (if my computer is ever returned to good health).

Today let us examine some of the "Tiny Greenhoods" (Speculantha sp. aff parviflora). As with most Greenhoods, this plant was previously known as a "Pterostylis". I have written about these plants many times, now, as there are numerous variant forms in the local area, and at Nowra (on the coast south from here). What was of interest was to see the form which grows here in shallow moss gardens on exposed sandstone rock shelves, within about 50 metres of the cliff faces.

Unlike the classic "form" of this species of Greenhood, which is simply green and white, this plant has distinct brown colouration on the top and front of the flower. It has small "ears" or "points" which do not protrude above the 'hood" of the flower (unlike the longer "eared" form I have shown previously, from near Nowra). When seen from the side, like this, you can see that the "sinus" (lets call it the gap at the front of the flower) of this form is not "stepped when viewed from the side" (PlantNET). Contrast it with this form of what is apparently the classic "parviflora" type of Greenhood - which has a very prominent step or protruding bulge in its "sinus".

The point about this location is that it means the plants are subjected to the full extremes of the weather - drying winds, lashing rains, and with a mere inch of soil below the moss, very little reserves of moisture to keep the plants alive over the summer. That latter condition of course, is what determines their predilection for flowering in autumn - after the heat has gone. To further highlight the tough conditions in which these plants live, if you look back at my earlier post about Manning Lookout, where I discussed Mallee Gums living there, you will see how tough and demanding is this localised "desert-like" environment (although it is a high rainfall area, these plants are living in a "virtual desert" on top of a sandstone cliff, with little or no soil). There Tiny Greenhoods are growing on rock shelves where not even the Mallee Gums can survive, but they are a mere handful of metres away from the Mallee Gums. There is a physical limitation to the size of plants which can survive on these exposed rock shelves, (insufficient soil to hold their roots - tall shrubs and trees would blow over), but tiny "heath" shrubs, and perennial plants such as Orchids and Sundews thrive amongst the mosses.
Here is the "Tiny Greenhood" as seen from the front.

By pushing the flower back slightly, I was better able to show you the "sinus" of the flower - it is not deeply notched, as some of these Tiny Greenhoods are. "Sinus shallowly notched when viewed from the front" (PlantNET) In fact this form does not appear to be "notched" at all.Here is a "mature" or ageing flower. The brownish colour has gone more red (which commonly happens in these brown forms of the plant). The "points" on the lateral sepals are just starting to protrude above the "hood". It seems to me to me to be unlikely that these points "grow" - so I assume that the "hood" starts to collapse as the flower ages, leaving the points protruding. I guess that is something which one could determine with some accuracy with a set of calipers, over a week of the life of an individual flower - but I have never done that measurement test.The point I am making about the variation amongst these related plants is that, in my opinion, there is ample evidence to classify them as different species. I know that David Jones, formerly from CSIRO and the Australian National Herbarium agrees, but he simply did not have the time to classify all these numerous variants from the "type" of the "Tiny Greenhood". He has retired now, but I understand he is still hoping to "publish" his conclusions on the revision of these "Speculanthas". It cannot come soon enough for me.

Another plant which was flowering abundantly at Manning Lookout yesterday is the Sunshine Wattle (Acacia terminalis). I mentioned this plant the other day, when discussing the "Sweet Wattle" which is just coming into flower on the Budderoo Plateau.

Here is a flower stem, with a fully opened head of flowers,
one set of partially opened flowers,
and one "head" with a single flower opened.

Next is a close-up study of the single opened flower. (Click to enlarge the image).
This image shows the buds of other flowers just starting to open.

You can clearly see the hard sheath-like petals from which the stamens of the flowers protrude.
These hard shell-like petals are permanent, and stay hidden by the "ball" of stamens which we think of as the flower. They do not fall, unlike those bracts which surround the buds in the "Sweet Wattle", prior to the true flower opening. For a more technical description of flowers of Acacia plants see this post, and this link to how the "botanists describe" Wattle flowers (see Fabaceae - Mimosoideae).
Here are some leaves of the Sunshine Wattle.

This plant has true leaves, not Phyllodes, as do the vast majority of Australian Acacias.

By the way, I do not know why this a plant is called Acacia "terminalis" - but I have left it to the end of this post to declare that fact!


mick said...

An interesting contrast in the subjects again - such tiny orchids which most would miss seeing even and wattle which which is hard for anyone to miss! Fascinating photos - again!

mick said...

Hi Denis, I'm back with another comment and maybe a suggestion. I really enjoy seeing your photos of the tiny orchids but as I am sure you are aware by now I know little or nothing about them. So I have trouble visualizing what they would look like in among other plants and especially the particular environment where you find them. Could you also photograph the area where you find them? Not huge big landscapes but just right around the plants? Or would this mean carrying around a different lens for the camera and would it be too much weight when you are wriggling around down on that oftentimes damp ground?? Thanks!

Denis Wilson said...

Hi Mick
Good suggestion.
I will try to remember to switch lenses and take a general view. I usually carry my bag with me, so it is no big deal, and it does help to complete the story.