zone 10-11... it will die outdoors ...

if it were me.. i would try to propagate it... from a cutting.. though the website below says its the wrong time of year .... and get rid of the monster ...

frankly .. in my warped world .. this is available for under 10 bucks in small size.. if you really have to have one.. it might be more pleasurable ... to just start over with a smaller one ... and see how the big one does in z5 winter.. lol ...

if it has some sentimental value... deal with it this winter... root a new one next summer... and then you will still have the same plant.. just a smaller version ...

i remember way back.. one of our first house plants.. struggled with this monster for years ... until we just got rid of it.. and made our lives so much simpler ...

good luck

ken

Here is a link that might be useful: link

Ken :
What will happen adversly if topped ? There are three main trunks all the same heighth and dia

In the mall of america there are planted specimens 40 feet high in the indoor amusemnt park, giving shade... These things WILL get too big in time.

It's a houseplant where you live, but I've seen them do ok as houseplants. Until they get too big, its a big tree.

Still you might not have to bring it in and out, you could keep it in for several years

Im zone 8b. Ive seen some decent size trees in lawns, 12-15 feet. probably bought as a living Christmas tree and moved into garden. But no way would your tree survive even one winter outside.

I like ken's suggestion. take a few cuttings and root them. When your house plant gets to big discard it and start a new one. It's what I did when I got tired of protecting tropical hibiscus plants.

at the link.. note the paragraph on propagation ... leaders do best to make a new, well shaped tree ...

with 3 leaders... you have three chances to replicate your plant ...

topping... is adverse to all tree people.. outside ...

indoors ... well ... hey .. who is in charge here anyway ... GO FOR IT ... if you make it real ugly ... you aren't that far behind my suggestion of getting rid of it anyway .. lol ...

all conifers.. will EVENTUALLY re-establish a leader.. or in your case 3 leaders.... how long.. no clue ...

IMHO ... you are a little late to try to bonsai a plant.. and that is basically what you are suggesting ... prune away.. play around... and when you hit the limit ... start over .. hence the suggestion of trying to root parts ...

good luck

ken

They start to droop at temps under 40F. When temps hit 32F. they are toast. I don't know why they call them a pine because they are not.

Dave

If you simply top one of the trunks it will develop two or even three leaders and they look ridiculous like that IMO.
South Florida is chocked full of storm damaged NIP's with multiple leaders- stupid looking trees this way :) IMO

but by topping or pruning it.. they can cope with it this winter in the hosue.. and still have stock to try propagation material next summer at proper rooting time ...

ken

How about throwing it out/giving it away and starting over with a new one? If you top the one you have and keep it, the problem is it will then be a topped tree, with a stump for a terminus instead of a natural branching structure. Maybe you wouldn't care how it looked then, but you will still have the same problem as with topping outdoor trees - it will try to grow back, and if able to re-sprout soon enough be back up to where it was. Then you have a deformed tree that is too tall, instead of merely a tree that is too tall.

Maybe there is a nearby facility with more room, that could give it a home. Or maybe even sell it over the internet.

As usual the GW has the best experts!!!
Not that this tree is so doggone special I can't just send it to the compost pile:) We might just yet,.............. interesting ideas, thanks guys (gals).
I tend to agree with cearbhaill and ken, sprouting a cluster at the top will look unnatural as it does in the big trees outdoors.
Propagation will be a fun project and B/H had the idea as bboy did that the Kansas City Zoo has one in the foyer.
Maybe one to match?............hmmmm
What would happen if I topped it and then sealed the cut with something like pine tar. Would that keep it from sprouting new leaders?

trees heal themselves .... and have an incredibly high survival function ...

NEVER seal a tree... it can take care of that itself ...

NOTHING YOU DO ... can stop it from re-establishing a leader ... short of repeatedly cutting them off ...

ken