I bet my BofP is 15 years old still growing leaves but has never bloomed. You're lucky !! Hubby bought me the plant pretty huge and says I must be doing something wrong but as long as it continues to grow large leaves something must be right..

I'm wondering how it would be if you reduced the stems to near the base and then went lower using a sharp mattock or even axe. I'm thinking of it as being in the same category as removing a full-size Phormium tenax - requiring serious effort. It does help to have a manual winch to keep tension on the plant while you chop the roots through - and to pull it clear. Sharp tools and great prudence. If someone with a 'calf-dozer' could access your small yard, then taking it out with the front scoop could be an option. Or hauling it out for you. The mini-size machines used for working in ditches and tight corners. You might find that there is a local company with the skills to work in constricted areas to remove plants past their acceptable size. (I hope they don't have to cart it through your house to take it away... I remember doing a job where I had to do that.) It would be worth a trawl through the Yellow Pages, perhaps. For the roots: Personally, I'd leave it for a season to see if there was any regrowth, then put fresh soil/compost into the area and allow natural decay to work for me. The other thing I'd be looking for would be the effect of the change in light density on the other plants in the yard, You may find some of them start into enthusiastic growth as soon as they get more light and water.

Strelitzia nicholai is commonly used as a large indoor foliage plant in California, where it can do quite well long term if it is treated well. If you have the room for it, I would suggest keeping it as an indoor plant rather than trying to "dwarf" it by letting the first frosts kill the tops from leaving it outdoors in the fall. They are relatively slow to regrow from the roots if they are frozen back to the ground, and as Cagary says, they don't divide all that easily as the roots are massive. I'd avoid fertilizing them much to try and slow their growth down, and give them enough light indoors so that the foliage doesn't become too floppy. The actual trunks take some time to form, and new leaves aren't really going to increase in height significantly if kept as an indoor plant. Unless you have early spring warmth, this plant is unlikely to recover well from being completely frozen back, although they regularly do so here in northern California conditions, but then again we are USDA zone 9b climate.

People are entitled to believe what they want to believe about what their climate zone is. I wouldn't make a claim that parts of downtown Sacramento could ever be considered almost a zone 10a, just as I think it is a stretch to consider my part of Berkeley a reliable zone 10a, although it may be 9 out of 10 winters. We are talking about Strelitzia nicholai here, the Ravenella simply doesn't tolerate northern California winters, the soils stay too wet and cold and they rot away. While there may be the occasional Strelitzia nicholai in downtown Sacramento up against buildings which benefit from reradiated heat and don't tend to look frozen back after each winter, the foliage will get zapped in a major way when temps drop below freezing here. In a hot summer area like Sacto, they will regrow new foliage more quickly, but the mature size will be restricted by being frozen back so often. This plant would really only be suitable as a long term specimen, in my opinion, where it is up against a wall or protected by an overhang or evergreen trees. Out in the open in a Sacramento garden, it will tend to get frozen browned foliage almost every winter, and 25F temps will kill it back to the ground. They can bloom at smaller sizes, I've seen 15 gallon sized plants in southern California that may only have had 3 feet of trunk blooming, as I've also had some that were relatively young and foliage topped out at 10 feet bloom here in Oakland. I've also got one in my front yard that has 10 feet of trunk that has never bloomed yet. Full sun, hotter weather year round and regular feeding will encourage them to bloom at smaller sizes, and also being planted in the ground. Not to discourage someone from planting one in a USDA zone 9b climate here in northern California, but be prepared to cover them if you don't like looking at burnt foliage for 6 months out of the year after a freeze. They do burn foliage right at 32F here in Berkeley, if it is more than just an hour or two.