Suggest you rent a electronic jackhammer at your local rental store. There are various heads that you can insert on the end of the jackhammer to facilitate getting the roots out. Also, many people will dig it out if you give them the roots/plant. Both private collectors, landscapers, and bamboo nurseries wld do the job for nothing. I'd start here before you put a lot of time and effort into a dig. I'd start by putting it on Craigslist in their freee category. I'd do a google on bamboo nurseries and contact any located in a 100 mile range.
Rgds

Are you really, really sure it's Buddah's Belly? Mine is several years younger than yours, but it has stayed very well behaved, as has my oldhamii. I have heard that some of the larger running bamboos will behave like clumpers for their first several years. Good luck!

Thank you fredgpops and tugbrethil for your responses. Yes, I am very sure this bamboo is Buddah's Belly. I purchased four 7 gallon size plants that were potbound, and all were exhibiting the swollen internodes then. Each pot was divided into two clumps and planted in a very rich soil. None of the new canes display the bulging. That does not bother me, but the all encroaching, ever present roots are a menace. Needless to say, I am very disappointed.

gcbunnell - Noninvasive is a relative term. Invasive is when a new shoot pops up 30 feet away. :) If someone told you the ROOTS were noninvasive they may have been thinking or speaking in terms of the RHIZOMES rather than the actual roots. Presuming you have Bambusa ventricosa (since you are in 8b) this is a fairly large bamboo (50+ ft tall), especially when it stops bellying. The clump will continue to get larger and larger in diameter as the plant gets older. You can cull the new shoots that come up where you do not want them but eventually you will need to renew the center.

Just like a tree with that much leaf area to support, a large bamboo requires an extensive root system to supply water and nutrients. Fredgpops has some good suggestions. The roots you encounter should be more fibrous than thick and woody, and so you may be able to cut though them with a sawzall or even a long sharp thin (sharpshooter type) shovel (or both) presuming your soil is not rocky. All you need to do is cut the roots not necessarily trench the area. If you circle the clump too closely, you may cut off the plant's water supply and kill it. In my experience Bambusas do not recover from dehydration as well as some other species. It may be better to just circle the area and kill the roots where you want to plant a new plant and water well until the new plant is established.

If the new culm is 3 feet away from the nearest other culm in the main clump then in my experience that would be very unusual for a B. v. unless perhaps you have been culling the new shoots as they come up on that branch of the rhizomes.

It may be that your Bambusa ventricosa has gotten too large for where you want to grow it and you should consider severely dividing the clump to make it smaller and moving it. This should set it back again for a number of years. As Fredgpops indicated you may be able to find someone who would do this free for the remainder of the plant. Check with your local ABS Chapter. If you are lucky you may find a nursery/bamboo seller willing to pay you a nominal amount for the plants they remove.

Good Luck

Mike McG near Brenham TX

Commonly sold Phyllostachys aurea produces swollen nodes. I would be very surprised if you did not purchase this species and mistakenly assume it was the other. This plant can spread all over in a hot climate. I once saw an entire small city lot in California with golden bamboo sprouts on some part of all of it.

I have Bambusa ventricosa 'wamin' which I believe is the real
Buddah Belly Bamboo in the same spot for 8 years now,and the
farthest it has EVER thrown a new shoot is less then a foot away from the clump. On another note it rarely throws culms
that are not 'swollen' like they should be. A friend close by
has had the straight species for 10+ years and it does about the same, about 12" max.
My guess is you don't have the real deal as someone else posted above. Just my 2 cents for what its worth.

Bambusa ventricosa 'wamin is a missnomer. To be "wamin" it must be Bambusa vulgaris wamin which is also called buddah belly. Hmmmm do we see the danger of common names here?

Anyway I also do not believe you have EITHER B, ventricosa or B. vulgaris "wamin". They are both medium tight clumpers and will not run 10 feet from the clump.