Tasmanian Plants

The weather on Monday (26 Oct 2009) was so nice and balmy today that despite having a splitting headache I chose to go for a short walk.

Having, in my absent mindedness forgotten how to get to the Knocklofty Park entrance, I settled for a short walk at the Leonard Wall – Valley Street Reserve.

The small reserve is relatively new and was erected in 2003 in memory of the well known ornithologist Leonard Ernst Wall (1921-2004).

The first impression of the place was that it is overun with weeds. Particularly prominet was the Meadow Foxtail (Alopecurus pratensis). This was the first time I’ve ever seen so much of this grass growing in one place. However, it is obvious that there have been some efforts to plant native species on the slopes of the reserve.

In all, I counted at least 32 species of weeds and 30 native species there (See checklist).

The highlight of my short walk must have been an old and imposing Blue Gum (Eucalyptus globulus) tree at the top of the reserve. It had ramified trunk right near the base and each trunk had a girth of say, over 2 meters. In the aerial photograph in the checklist page, the crown of this tree can be seen to cover a significant portion of the small reserve.

By the size alone I doubt this Blue Gum was planted. If it was it must have been planted about a century ago. I imagine the tree must be a remnant of old Hobart, and has borne silent witness to all the changes that have taken place for the past century.

What would such trees say if we could hear?

It is common knowledge that the grassland ecosystem is one of high botanical biodiversity. Even disturbed grasslands can have a rather high diversity of a mixed bag of native and exotic plants.

Whilst strolling along the side of a 300m stretch of road in the Queens domain I decided to do an amateur-naturalist survey.

I took the road as an informal transect and count the number of grass genera that I could discern along that 300 m stretch, just on the side of the road I was walking.

I collected some of the grass and laid them out to photograph, as shown below.

Here are some of my results of the impromptu identifications, with the numbers corresponding to the genus identity of the grasses in the photograph:

1. Greater Quaking-grass (Briza maxima)
2. Lesser Quaking-grass (Briza minor)
3. Poa bulbosa
4. Sweetgrass (Glyceria sp.)
5. Silvery Hairgrass (Aira caryophyllea)
6. Poa sp.
7. Fescue (Festuca sp.)
8. Cocksfoot (Dactylis glomerata)
9. Kangaroo grass (Themeda triandra)
10. Speargrass (Austrostipa sp.)
11. unknown sp.
12. Loose Plumegrass (Dichelachne inaequiglumis)
13. Rice millet (Piptatherum miliaceum)
14. Great Brome (Bromus diandrus)
15. Ratstail Fescue (Vulpia myuros)
16. Bearded Oat (Avena barbata)
17. Sweet Vernalgrass (Anthoxanthum odoratum)

Although only 17 species are featured in the photograph, there is not a shadow of doubt that I have missed quite a few species.

For example, there were definitely more than two species of Speargrass (Austrostipa) and a few other more genera that I had seen previously when walking along that road.

Nevertheless, just on the basis of what I have collected and laid out there are at least 14 genera of grasses, all just on one side of a 300m stretch of road!

Such richness!

For a fan of biodiversity (weedy or not) and of grasses, a ramble around such a grassland in springtime is simply irresistible.

Saltmarsh at South Arm with Sarcocornia (Glasswort) herbfield

In saltmarshes, there is always something worth looking out for. I have written about one such plant, the Silky Wilsonia (Wilsonia humilis) in a previous post.

When I went for a walk on the 11th of April 2009 at South Arm, Calverts Lagoon, I was delighted to find another rare saltmarsh plant, the Golden Dodder (Cuscuta tasmanica), which occurs in only a couple of other localities in east and northeast Tasmania (See DPIW’s listing statement).

Golden Dodder hails from the morning glory family (Convolvulaceae), or so it will be revealed upon examining the flowers. I revisted the lagoon when the Golden Dodder was flowering in December the same year just to convince myself of that. I can’t say I am extremely convinced as the plant does seem to be very different looking from other members of the morning glory family. Molecular work however does seem to support the placement of Cuscuta within the morning glory family (Stefanovic et al. 2003). Some botanists consider the genus Cuscuta to belong under it’s own family, the Cuscutaceae.

Disposition-wise however, the Golden Dodder is far from the blooms that glorifies the morn.

The Golden Dodder is a parasitic plant of the first grade. Plants such as the Golden Dodder are called holoparasites, that is to say they do not have functional apparatus for photosynthesis and thus rely entirely on their host for food. Moreover, the Golden Dodder and other members of the Cuscuta genus lack internal phloem, the conducting vessels that transfer food within the plant.

The Golden Dodder thus relies on specialized root-like outgrowths called haustoria which penetrate into the tissues of their host. Talk about a botanical vampire.

I’d call the Golden Dodder the saltmarsh ‘gory’.

A blazing patch of Golden Dodder

The foreboding recognizability of the Golden Dodder precedes its parasitic nature. Despite having no obvious leaves, this plant is immediately recognizable, even from a distance.

In a patch of uniformly green saltmarsh herbs, the Golden Dodder stands out like a blazing orange plague.

When my gaze first fell upon those bright orange chlorophyll-lacking stem threads, the first word that flashed in my head was ‘Pestilence’.

Too strong a word perhaps, but pestilent or not, the form of the Golden Dodder and their place in this unique ecosystem piqued my natural curiosity. I wondered what role these plants play in the ecology of the salt marsh.

The salt marsh is, on its own, a physiologically harsh environment for plants. Salinity has driven various unrelated families to resort to succulence, that is to say, using stored water in their succulent leaves to dilute the salt taken up from the soil.

A number of plants like of Sarcocornia (Glassworts), Disphyma (Pigface) and Spergularia (Seaspurrey) among others, have found succulence to be a viable means of dealing with salt and has thus come to dominate the saltmarshes.

The Golden Dodder in it's full 'gory'

From a scientific perspective, a number of interesting studies that may be undertaken. For instance, the host plants themselves probably have very concentrated sap by conventional standards. What does this then say about the the physiological mechanisms of the Golden Dodder? How does it deal with salt, if it absorbs any from its host?

Flowers of the Golden Dodder

Interestingly and perhaps incidentally, the preferred host of the Golden Dodder is the Narrowleaf Wilsonia (Wilsonia backhousei), another member of the Morning Glory family. Some family feuding going on?

Much still to learn of these wonderful plants in this wondrous natural environment.

The 23th Dec 2008 marks my first visit to the famous Cataract Gorge, Launceston. It’s almost shameful that I lived on this beautiful island for 4 years before paying the gorge a visit.

As I didn’t have much time I merely took a short walk  along the tourist track. The first thing that struck me botanically was the the exuberance of exotic ornamentals. There were whole colonies of  Red Velerian or Kiss me Quick (Centranthus ruber), Blue Periwinkle (Vinca major), Blackberry (Rubus fruticosus aggregate) and more.

By way of native plants, I was most delighted to see the Common Raspfern (Doodia australis). This would be be the first time I am seeing this fern growing naturally.

Also, I was struck by the preponderance of a native moss, Rhacocarpus purpurascens, growing on boulders there. This moss is more often found growing in alpine tarns (see my post on this moss).

My honours project supervisor, Paddy Dalton, told me that he collected this moss in fruit once for this locality. Personally, I’ve seen it scores of times on Mt Wellington but I’ve never seen capsules. Could there be something interesting going on here?

I’ll be back for another visit sometime.

Blue Lovecreeper

There is a nice bit of Silver Peppermint (Eucalyptus tenuiramis) woodland near the Cascade Brewery which I love checking in on. This year I thought I’d go up and have a look around in the hope of seeing some orchids, particularly the Dark Caladenia (Caladenia atrata) and to relocate a very small species of Leek orchid (Prasophyllum sp.) which I had seen a couple of years ago. Alas, it was not the right time – there were no orchids in sight.

Starry Appleberry

The bush didn’t let me go away empty handed however. The Starry Appleberry (Rhytidosporum procumbens) was in full flower. It’s not a very big plant but the white flowers are unmissable. It’s sometimes hard to imagine that this little shrub is a relative of Tasmania’s Pricky Box (Bursaria spinosa). The Blue Lovecreeper (Comesperma volubile) and Peachberry Heath (Lissanthe strigosa subsp. subulata) were also getting started. This twiner would easily be mistaken for dodder (Cassytha sp.) when not in flower.

Breutelia affinis

It wasn’t long before the bryophyte bug bit and I started getting distracted by some of the fruiting bryophytes around. In particular, there were some delightful capsules and antheridia (male reproductive parts – pic left) of Breutelia affinis and some fruiting Fossombronia.

There are new wonders every spring, even in places one has frequented. I’ll be back again for sure.