Tuesday, 10 May 2016
Brilliant salvia look-alike from Tanzania
The Uluguru Mountains of Tanzania are named after the local Luguru tribe, both of which are located in the middle-west of Africa, just south of the equator and east of the Congo, about a hundred kilometres from the Indian Ocean.
These mountains are best known for their wildlife - from odd sunbirds and shrews to rare frogs and millipedes - but it has an interesting flora as well. Over a hundred plant species are found only in the mountain range, most of them in the high-altitude (1200-2500 metres above sea level) rainforest.
Brillantaisia ulugurica, although named after the mountain range named after the tribe, is not restricted to just this area. extending elsewhere in Tanzania, as well as Democratic Republic of Congo, Rwanda, Burundi, Uganda, Malawi, Mozambique, Zambia and Zimbabwe. It seems to favour damp areas under or at the edge of tropical forests, and grows down to 700 metres above sea level. It's large floppy leaves suggest a moist, protected habitat.
It and other species of Brillantaisia (do take a look at my post* from Kew Gardens, about another species of this attractive genus) are often called Giant Salvia due to their big (up to 10 cm long), bold, salvia-like flowers. In fact they are classified in an entirely different family, the Acanthaceae (not the mint family Lamiaceae). The family Acanthaceae includes things like, well, Acanthus (Bear's Breach) itself, but also Thunbergia, Justicia, and these days even the mangrove genus Avicennia.
Most of the family Acanthaceae have leaves in opposite pairs that alternate at right angles to the pair below and above - what we call decussate. You can see this pattern in the plant from our Melbourne Nursery, in flower and photographed in January this year.
The flowers are of course the main attraction, for us and bees. It seems this genus is mostly bee-pollinated, with the two halves of the flower articulated to make sure the insect visitor comes into contact with the plants reproductive bits (thereby carrying pollen from one flower to another - generally a good thing...). I wonder with a big flower like this whether humming birds get into the act as well. Or maybe its left to the bigger bees, like bumble bees.
In this close up, you can see two elongate stamen-like things (carrying the anthers, with their pollen) sticking out the top. I understand flowers of Brillantaisia have two fertile stamens and two that are just for display (staminodes), and that the latter are deeper within the throat of the flower.
If you look at the top picture, though, you'll see the female receptive bit (style) way above the flower throat. There must be a bit of mechanical action going on when the bees visits the flower looking for nectar, bringing the style and the stamens closer to its body. I didn't think to dissect the flower or watch a bee visit when I took these pictures. I was simply overcome by the giant, purple blooms!
And in case you are wondering, the genus name has not an illiterate reference to these rather brilliant flowers, but commemorates a 19th century French botanist and explorer of west Africa, Brillant-Marion. As he may have discovered on his travels, other species of Brillantaisia are included in a local plant and snail concoction to treat small-pox. Although my source seems to be a little sceptical, noting that this was 'doubtless effective after the global eradication of smallpox in 1979'.
Note: Our specimen was kindly donated to the Royal Botanic Gardens Victorian by our friend and supporter, Meg Bentley. It's in our nursery at the moment but we hope to get it out into the public garden areas as soon as possible.
*I wondered then, in that first post on this genus, where the name Giant Salvia came from. I know know - a different species!