Christmas Bells

Christmas Bells
Christmas Bells - Blandfordia nobilis

Monday, November 03, 2008

Tubular Flowers

I was struck by the superficial similarities between the form of two flowers which were both flowering on the same day, last week, in my yard. As these plants are not classed by the botanists as being related, I assume that their similarity is an example of parallel evolution, where plants have adapted similar basic external flower form (but not in terms of their more complex internal structure) to suit similar needs (in this case, presumably to do with pollination).

The first is what I regard as a choice garden plant, the "Chinese Beauty Bush". It is named
Kolkwitzia amabilis (after a German Botanist) but it was only introduced to Europe in 1901, from China, by the English plant hunter Ernest Wilson. Wilson is most famous as the principal collector for the Arnold Arboretum in Boston (Mass.) USA. This plant is classed as a member of the honeysuckle family - the Caprifoliaceae.
Unlike the flower below, this plant has prominent stamens held high in the throat of the flower. This flower has really prominent hairs on the lower side of the tubular flower. Compare this with the flower below.

This plant produces fruits which are small rounded capsules which are very hairy, allowing them to be dispersed by catching onto passing animals (including humans). In that way, their seed capsules resemble the annoying habit of Myosotis ("Forget me Not") - but that plant is not related, being in the Boraginaceae.

The second plant which I photographed that day is the Wonga Vine (Pandorea pandorana). It is a local climber, in the Bignoniaceae family. This plant is capable of growing to a huge size, indeed one of the first jobs I did when I moved to Robertson was to rescue a large Sassafras tree which was being smothered by a huge Wonga Vine. I cut the trunk of the Wonga Vine (with some difficulty) because the trunk was more than 6 inches thick. Subsequently, the Sassafras has outgrown the skeleton of the now dead Wonga Vine. These photos were taken on a much smaller plant which is growing as a scrambling vine, growing through a series of mixed shrubs just over head height, with the flowers in full sun. Both flowers being discussed today are tubular, with prominent hairs (bristles) on the lower inside edge of the tube. Although the bristles on the Pandorea appear to have golden tips, they are NOT stamens (of which the botanists assure me there are only 4) - which apparently are held deeply within the tubular corolla (unlike the Kolkwitzia).

As a naturalist (not a botanist), I am curious about how both these plants are pollinated, but I do not have any information on that aspect of these plant's life cycle. I assume that the Wonga Vine is pollinated by moths, as the flowers are white coloured (increasing their visibility at night), and many moths have a long proboscis for reaching into the centre of a long tubular flower. Certainly, their flowering period coincides with a peak in moth populations. Being a climber, this plant regularly reaches high into the tops of local rainforest plants, and then it flowers right at the top of the host plant. This has an advantage for moth pollination (greatly increasing its visibility at night), as well as for seed dispersal.
I do know that these flowers produce seed capsules which split open to release flattened winged seeds which are very effectively dispersed on the wind, in hot summer days. I have witnessed huge numbers of seeds being blown across open ground from seed capsules splitting on a hot day, allowing the wind to carry the seeds as much as 75 metres away from the parent plant.

I cannot say that this plants seeds provide food for the Wonga Pigeon, but I can say that they both occur in my yard.


mick said...

Lovely flowers - again! - and very interesting details about them.

Duncan said...

The Wonga Vine can really take over Denis, it's about time I cut mine back.

Denis Wilson said...

Thanks Mick. I find the whole business of parallel evolution fascinating.
Duncan, I certainly agree - the one I had to cut off at ground level was smothering a 40 foot Sassafras tree. Amazing. Obviously very old, but they will get that large here, if left unchecked. Normally I would leave them to their own devices, but in this case, it was the Sassafras closes to where I would eventually site my house - so the tree is an important part of my landscape. Further down in the bush, and I would not have intervened. But if they are covering a structure, or other plants, then I am with you.
Not as fast as Wisteria, for example, but ultimately, just as destructive, if left unchecked.
Pretty flowers, though.