Hmmm....not a pro here but taking it to 10-15' doesn't sound good at all. Also, I think you want to trim it during the winter months when it's dormant. They are pretty trees...and definitely everywhere here (we're just east of Pasadena). Hopefully someone here will know more. If not, your best bet is to consult a good tree trimming company or arborist. We have a friend with a couple huge jacarandas like yours. She does have them trimmed back quite a bit, but not anything close to what you're asking. It's amazing how fast those trees fill in again after the trimming.

Lots of info online...like these links.

https://www.gardenguides.com/12550605-when-to-prune-a-jacaranda-tree.html

https://homeguides.sfgate.com/trim-jacaranda-tree-42980.html

Yes, it will probably survive. But I seriously doubt you will be happy with the look. Or the upkeep. Those 'suckers' it keeps sending out are in response to the pruning it has already received - that's what jacs do. In fact, various websites will instruct you not to prune at all: "Forget about pruning jacarandas altogether or you will spoil their good looks, and the tree’s shape, forever. When you prune a jacaranda it then sends up vertical shoots (you’ll often see the effect on jacaranda street trees which have been pruned to make room for overhead powerlines). The normal shape for a jacaranda is that of an elegant umbrella, and the appearance of vertical branches ruins its good looks. Your only solution, if you have pruned a jacaranda, is to persist in cutting off the vertical shoots."

I'd consider removal altogther. What you propose will not be a one shot affair and you will need to continue to prune and clean up after the tree going forward.

Somebody local did just to an old fat trunked tree a few years ago. It grew back..but you see huge amputated stump branches that of course grew out like a witches broom,thick in small branches.

They are best left alone..but,you could thin it out,removing whole inner branches and giving more light underneath to other yard plants..with no real shock to the tree. Just get a tree trimmer with a good artistic eye and plant knowledge.

I don't have Jacaranda experience per se, but LOTS of radical cutting experience. In terms of regrowth, I bet you could cut it to the ground and it would bounce back in some vigorous form. The question is how, really, do you want it to look? What are you trying to create? Can you doodle out a simple line sketch of the form you're hoping for?

I had a royal paulownia -- a weedy, fastest-growing-ever tree -- that I made into a multi-trunk and then pollarded to control size and create mind blowing characteristics ... gynormous leaves for one thing. It was a gorgeous thing and is a most missed plant. (I moved. Wish I could have it again!) Was cutting it at 10' above grade and if I recall correctly, the one-year growth branches were about 13' length ... so that's 23' total height instead of 60-something feet, or whatever they get. It started as a huge tree that came with the property, with a 2' or thereabouts diameter trunk. I cut it to the ground to experiment with regrowing in the form I wanted. Had it died after I cut it, I would have said "Oh well," as it was profoundly lopsided and in my estimation, the form was about as homely as could be. But in bloom it was too spectacular to not want around. After I cut it down, there came a lot of sprouts from roots, but I zapped them with Roundup almost as soon as they appeared, as I had no interest in a forest of "weed" trees.

just some tree lore.. no idea about this plant nor growing in CA ...

not many trees or shrubs.. die due to cutting back.. no matter how far ... barring some other problem ...

with no insult to the huge root mass ... which could be twice what you see above the ground ... being a tree ... you would probably be surprised how fast this thing could grow back ... and probably even faster considering your CA year around growing season ...

with no pic.. and only your words to go on ... i would probably agree.. that it is time for it to go ... personally.. i dont like repeatedly spending a fortune on trying to maintain a plant that in all reality.. just p.o.'s me ... every time i look at it.. so the last usual investment.. is removal ...

you can replant something new.. maybe 2 .. and mother earth.. net no loss and maybe plus one ...

ken

Like gardengal said, it will look like crap because of all the water spouts. Jacaranda should be pruned rarely if at all. Take it out and replace it with a tree that will fit the space when fully grown.

"The question is how, really, do you want it to look?"

That would definitely be key to me.

Thanks, all - definitely seems like I'm in wishful thinking territory here that it would not only survive and grow, but also be aesthetically pleasing at the same time.

The tree was already in place when I bought my house and was obviously never tended to the way a Jacaranda should be - it has a low split trunk and had just suffered through a major hacking job when I moved in (probably to clear the canopy when trying to sell the house). At full size, it's also arguably too large for the yard size and overhangs the house and the neighbors' yards (not by a lot, but enough to drop on everyone around me, too), and the power line growth is one of the major concerns for me.

I do love the trees when they're in bloom, though, which is why I was hoping not to go to the extreme measure of full removal. Will have to consider whether to take the chance on extreme cutback, see how it goes and then remove later if it ends up looking awful. If I do, I'll wait until its off-season and hope it miraculously comes back small and beautiful in the Spring... :)

""At full size, it's also arguably too large for the yard size and overhangs the house and the neighbors' yards (not by a lot, but enough to drop on everyone around me, too), and the power line growth is one of the major concerns for me. "

You answered your own question there, really. The tree is a problem and a hazard in several ways. Do as Nil suggested: have it removed and plant something that will mature at a size appropriate to the space available. Short term pain, long term gain.

If you must, there is a dwarf Jac 'Bonsai Blue' that grows to about 10'-15'.

Today in Haytown:

I thought of this topic as we were driving around today. Jacs are truly everywhere.

Plus the fallen blossoms reek of cat piss.

One more. Not for people who like plastic trees!

If you like the Jacaranda but don't have room, there is a dwarf cultivar called 'Sakai01', sold as Bonsai Blue.