18 June 2024
The OTHER stinky flower putting on a show at Kew
Alongside the iconic Titan arum, meet another foul-smelling flower that's making its debut this June.
A week in mid-June marked an exciting event for us in the Palm House: our Aristolochia goldieana flowered for the second year in a row.
Native to Tropical West Africa, this vulnerable species was first described in 1865 and is one of the largest Aristolochia species known.
This is only the third time this species has ever flowered in the UK, with the second being last year and the first back in the nineties in the Princess of Wales Conservatory.
Our plant, a scrappy looking climber, hides in the back of Bed 15 in the African section, largely not doing anything save growing a couple of feet each year. It has only been in the ground for around three years and, although it was pruned a little in 2022, it largely keeps to itself, and is now about four metres tall.
Small but powerful
Now, for anyone with any experience of Aristolochias, this is pathetic.
Aristolochia grow throughout much of the world (including Europe) and are known for mostly being rambunctious vines that twist around anything they can find. Aristolochia goldieana, however, tends to have a more compact growth and flower towards the base.
If you visit the Palm House, you might have noticed the A. tithonusiana flowering by the North door in the winter, a vine with a similar habit but tiny flowers the size of your thumb.
This year, our A. goldieana looks excellent, and has grown notably more than normal. This is likely a sign that it is fully settled into its position now and has a good spread of healthy roots down. The vine has quite a bit of sunlight and space around it, especially at its base.
Inside the Aristolochia
Aristolochia blooms are very easy to recognise once you know what to look for. You might know the Artistolochia grandiflora that was once in the Waterlily House, or behind the Princess of Wales Pond. They have alternate, heart-shaped leaves and cavernous flowers.
Each inflorescence is carried in a complicated structure that has earned Aristolochias many common names, such as pelican flower or Dutchman’s pipe.
While the foliage smells bitter and of chemicals, the flowers smell like a garbage heap in high summer. Aristolochia uses the same method as many well-known aroids, including the Titan arum, to deceive their pollinators. Even the giant Victoria waterlilies are comparable, though with a nicer scent.
The trap is sprung
Pollinators are attracted by the sweet smell of decay, and the dark conical entrance seems to entice them further. Gnats and small flies (there were many bluebottles attracted to the A. goldieana), travel deeper into the structure.
They pass through a tube lined with hairs, known as trichomes, before arriving in a wide chamber known as the utricle. This is where the male and female parts of the flower are located, in a structure called the gynostemium.
The female parts of the flower, the stigma, are sticky and capture any pollen that the flies have brought from previous flowers. But the pollinators cannot escape until the pollen from this flower is released.
Artistolochia traps the flies in the utricle for up to 24 hours to ensure pollination. Whilst the stigma is active, the trapping trichomes in the tube all face downwards, allowing the flies in, but not out.
Once the stigma begins to dry, the pollen is released. Only then do the trichomes begin to wither, finally allowing the flies to escape and visit the next flower.
Two attempts at pollination
Last year, when this Aristolochia goldieana flowered for the first time, two flowers were produced over the week. I attempted to pollinate the second bloom, once by using the pollen from the first, and secondly by self-pollination. Neither attempt worked.
There are many reasons as to why this may be the case. From some very quick research, some Aristolochia are not self-compatible. Timing of pollination events are likely incredibly important.
Although both attempts were completed at very different times with this in mind, perhaps I got it wrong. In the future, we could experiment with pollen storage, though I have not seen any scientific papers covering this with regards to Aristolochia.
A goldilocks greenhouse
We should also consider the health of the plant as a whole. With this being the first flowering event, perhaps the plant is not mature enough to produce fruit.
External factors may also have played a part. The weather dipped a little after flowering in 2023, maybe the watering changed now that we were focussed on the plant, or perhaps it needed much more feed than we realised at this growth stage.
Another entirely valid option is that it just didn’t work this time round. Living things often have their own minds about these things.
In a way, I am quite relieved. My fear would have been that it would be too much effort for the little thing, the seed would be sacrificial.
As it is, our plant is still healthy, and gaining in strength. Perhaps now our A. goldieana has reached this ‘goldilocks’ period, it will flower again. And again. And again.
So while it'll only flower for a few days, perhaps next year, you'll be able to spot this pungent giant in the Palm House once more!
.jpg.webp?itok=QOasOS6F "Kew horticulturalist working in Kew’s Waterlily House pond © RBG Kew")
