For those that are interested in the Lasiodeae subfamily, there is an interesting new species entering cultivation this year! Known as Cyrtosperma giganteum, this herbaceous behemoth is native to the island of New Guinea. First described in 1910 by Adolf Engler, this huge plant boasts giant, leathery leaves (an English translation of his description can be found here). Although only recorded from the Lorentz river in Papua, Indonesia, it could be possible that the range of this species extends further.
As I do not own any photographs of the adult plants, all I can do is informally describe it and link to websites that do have photos. The plant somewhat resembles a more robust version of C. merkusii, with stouter petioles (although the height of the leaf blades seem to almost make up for this). From what I can gather, the inflorescence is the largest of the genus. I’m not sure if this species is solitary or clustering, hopefully the latter but I’m sure it’ll become apparent as it grows! Photos in-situ show multiple plants growing in close proximity, but I’m not sure if they are clones or separate individuals. I’ve also seen a young plant growing in captivity with an offset growing from a node on its rhizome, which suggest this plant does have the ability to cluster. The blades and petioles appear mostly unarmed, at least from what I can see in photos.
There is very little information available for this species at the time of writing (September 2020), so this post is currently quite short! Hopefully with time I will be able to edit and expand this post as I obtain more photographs and figure out how to cultivate it. Although some of the most famous Cyrtosperma species are helophytic, many are not, so I’m not completely sure about how to cultivate this species as I certainly don’t want to drown it.
Recently, I scraped together to obtain 10 seeds originating from ex-situ plants in Papua, which has made my year! They were originally sold as C. merkusii, then as “sp. Papua”. They are yet to make their first true leaves, but seem to be happy growing in sphagnum. The seed is typical of many Lasioids, having a curved shape and a warty seed coat.
So, wish me luck. I will endeavour to update regularly and record my progress!
Update 11.10.2020
The first few seedlings unfurled their leaves today. They seem to be happy in indirect sunlight with some supplemental overhead lighting. The sphagnum they’re in is pretty damp, but the roots seem to grow faster when the moss is wetter. I’m looking forward to seeing how the leaves develop as they mature.
Update 27.08.2021
After potting my seedlings up, most collapsed and left me with one plant, which has grown to do quite well. It could be because I kept them a bit too dry, or perhaps a pathogen got to them. The box I was growing them in didn’t have much in the way of ventilation.
Update 22.02.2022
After being shaded by its hardier relatives C. merkusii and C. johnstonii, this plant looks a bit worse for wear. I think the cooler temperatures, lack of feeding, and tiny pot size haven’t helped either! I’ve been away a lot for work and haven’t given many of my plants the standard of care they deserve in recent months.
Today I noticed a new emerging leaf which I’m hoping will push past the “canopy” of other Cyrtosperma species and allow it to soak up the returning spring sunlight. I’ve started to feed gently again which will hopefully help it to produce strong new growth. The plant is producing thick roots around the base, which are helping to re-stabilise it.
Lost and Ferned 
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