You could try cutting off some of the leaves and carefully paint the cut stems with weedkiller. I've seen this done with privet, the weedkiller is supposed to be painted on as soon as the cut is made.

They have a deep and tenacious root system. To actually remove it would require a football side armed with crowbars, or a small backhoe. If you don't want to risk the rock waterfall then you may, as anthurm suggests, have to do your best to kill it through cutting and poison. That won't remove the root system which would probably take years to break down and rot away. In the meantime you won't be able to replant anything there except on top in pots. Unless a stump-grinder might work - you'd need to get an expert in for a look (those make a lot of mess though you'd need to protect the pool area from the pulp)

I have a couple the same size so I can picture your situation.

Consider cutting it progressively with a machete until you have it down to the stump. I would give it a little time and see if it wants to shoot again and then consider poison.

We have cut several Cocos Palms down over the years and some we have cut out the centre of the stump and planted Bromies or succulents. Made a feature from the stump. They rot aware in time.

Nod

A lot of hard Yakka. the method I used was to remove the outside
leaves- the roots themselves are tuberous and plentiful Remove
til the monster is manageable and go to work with the crowbar.
Good luck!!
chas

Hi
assume you're referencing S. nicollai white bird of paradise and not Ravenala madagascrensis or Phenokaspermum??
Nicolai can be removed slowly by keeping it cut back while the other two require MAJOR digging lol you will end up with a hole but can be filled over time
Had to hire a backhoe for ravenala. ended up with a hole 2 meters both ways lol
Haven't removed the s. american one as yet as they are so rare at least around here
keep cutting you'll win eventually !!! gary

If a plant doesn't have leaves there's no photosynthesis, and no photosynthesis means no food to the plant and it fades away. I did it with a Bougainvillea, also covered the stump so no light got to any new leaves trying to come through. It took about 3 years before the plant was dead, and a few more years before the stump rotted out. It may not be much faster with a Bird of Paradise. Poisons will short cut the process, but there's also a downside to poison. Depends on how fast you want the process.

I removed mine about 18 months ago, it wasn't as tall as yours but it was fully grown - the smaller version, Strelitzia reginea, yours sound like s. nicolia; grows much taller, has white flowers. All the advice I had was that it would be a monstrous job but I attacked it anyway. I cut it down to about metre or less tall, soaked the ground all around with water and then attacked it with a good, strong, 2 metre crow bar and was surprised at how relatively easy it was to prise out. Some of the deepest roots I left which have now pretty well rotted away and improved the soil and what I planted in its place is now coming along nicely, if a little slow (Sorry, can't think of the name of what I replaced it with).
B.