Monday, February 19, 2007

Two Conospermum species, plus a botany lesson

Conospermum or Smokebush belong to the spectacular Proteaceae family.

There are more than sixty smokebush species occurring in most Australian States, but are most numerous and diverse in the SW region of WA (the wheatbelt). Generally they are low to medium sized shrubs, often with striking floral displays that are used in the cut flower industry. There are several species in the Esperance region, but two outshine the others when it comes to display. These are Conospermum distichum and Conospermum teretifolium.

The Conospermum distichum smokebush is a bushy shrub growing to less than a metre and usually (in the Esperance region) occurring in small colonies on deep sandy soil. It mass flowers during spring producing a striking bluish grey (smoky) floral display.

Smokebush, Conospermum distichum

Conospermum teretifolium the Spider Smokebush grows to over a metre, also on deep sandy soils, but as scattered plants or only a few individuals. The flowers form in dense creamy white heads during late spring to early summer.

Spider Smokebush, Conospermum teretifolium

Like most people interested in botany, I have often been caught out on identification. On occasion I have seen (to me) a new species and on keying out the botanical features, it eventually indicates that it belongs to this or that family. But being familiar with some species and genera within that family, I think it can't be as it looks nothing like them. So believing I have made an error, I retrace my steps, only to arrive back again at the highly suspicious family. So reluctantly I investigate, only to find the key was correct and I had encountered yet another variation of the taxonomic features.

These two Conospermum species are also very dissimilar, but now have a look at the flowers, first the C. distichum smokebush. Note the small petals and densely woolly flowers.

Now the Conospermum teretifolium the Spider Smokebush, see how large the flowers are in comparison, with no hairs and the long thin petals.

So how come these completely different plants have been placed in the same genus? The secret is in the structure of the flowers, and this applies not only to these two species, but also to the hundreds of other species in the large Proteaceae family. These Proteaceae plants are found in several countries, although Australia and South Africa have the greatest diversity of species. These include the Australian Banksia, Hakea, Grevillea, Isopogon, Persoonia, Conospermum, etc, also the Protea, Leucospermum, Leucadendron, etc, from South Africa.
The similarity of these plants world wide, is they all have four perianth-segments (4 petal-like structures), with four stamens that are either attached directly to the petal-like structures, or to the perianth (flower) tube itself. There are other features like a superior ovary (where the floral tube runs uninterrupted to below the seed bearing structure, ie the ovary), but basically you have 4 petals + 4 attached stamens.

Now the main differences between the genera relate to the seed and/or, the seed bearing structure, which with Conospermum is a hairy obconical seed/nut. Conospermum in Latin means a cone [shaped] seed.

Therefore both these very different looking plants, have with close examination, 4 petals + 4 attached stamens + obconical seed/nuts!

Why not checkout the above features on the Proteaceae plants in your garden or bush? Then look at the different seeds and seed carrying arrangements. So now you should be able to recognise any Proteaceae plant from anywhere in the world, even if you have never seen them before.


Anonymous said...

yep it proves again, that some day i'll have to check out the flowers in WA.... owadefa

Esperance Blog said...

Hi owadefa, WA is an amazing place particularly if you are into botany. Proteaceae are very common here, so plenty to keep you occupied.


huntervalley said...

hello Jack, a very interesting article, and I just love the Conospermum. They have such a delicate habit in what can appear a harsh habitat - a real contrast.

I have just pulled a grevillea flower from my garden apart with tweezers. It has 4 tiny petals (which I have never taken the time to notice before, so thanks), but it appears to have only one stamen (a very long one with a 'knob' on the end). Can you please explain this. It doesn't appear to be 4 stamens fused together.


Esperance Blog said...

Hi Huntervalley, good to hear of your investigations and thanks for coming back with your queries, as this is the only way for me to know if I have explained it clearly.

The single long stamen you mention will be the style and if you follow it down to its base, you will find the ovary.

With many Proteaceae like Grevillea, Banksia, Hakea, etc, the stamen is reduced to just an anther, which you will find embedded at the ends of the petal-like segments.

The stamens are not fused together, but attached to the perianth (flower-like structure).

Please let me know how you go.

Anonymous said...

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Esperance Blog said...

Thanks ocean and forest walks, pleased you liked it.


huntervalley said...

I've just checked a grevillea closer, and, no, I can't see anther or stamens, just style and 4 petals. If it is a hybrid will it still get all reproductive components?

When a different variety of grevillea flowers in my garden, I'll check it out. I also have a banksia forming new flower stalks, so will check them out also.


Esperance Blog said...

Hi Huntervalley, that is strange as the anthers should be attached at the tip of the petal-like segments. Not sure what the hybridising experience would do in this regards, please let me know what you find on a fresh flower.