Pachypodium saundersii or Kudu lilies are native to my country and relatively easy to grow, we can even keep them outside in the garden all year round if there is a hot, sunny, area that doesn't get frost in winter. They don't mind being outside in the summer rain, as long as the growing medium in the pot drains well and they must be kept dry in winter when it is cold. Kudu lilies are very slow growers and only flower when they are 4-5 years old. I got this one almost 2 years ago and looking at the picture below, which I took when I got it, you can see just how slow growth is. Kudu Lilies lose all their leaves in winter, leaving the naked caudex and stems, that's why the leaves are turning yellow, it will be winter soon and it's flowering before going to sleep until next spring.
Stems tend to grow sideways with this plant, instead of straight up although the beauty of these caudiciform plants is that no two plants are ever alike.
Looking at the flowers, it's clear that they are pollinated by moths: the white colour is only really visible to nocturnal insect pollinators and the tiny hairs in the floral tube are there to deter other insects from crawling in.
The floral tube from the side:
The floral tube is long and the flowers fairly large so it is probably pollinated by one of the larger moths, probably one of the Sphinx Moth family. I'll try pollinating the flowers with a cat whisker to see if I get any seeds forming.
If you look closely, you'll see that it has a small infestation of white scale, a pest you normally get on aloes. I haven't had any luck getting rid of it with water-based insecticide and because I can't get oleum during lockdown, I'll try plain cooking oil: apparently that works too. If you're wondering what the plant on the side is, it's a Bushman's Candle, Monsonia vanderietiae. It's been cold and rainy and I moved these two under a roof to keep them drier because this kind of weather tends to provoke rot in caudiciform plants