To prevent bamboo from spreading, the most effective method is to install a physical barrier, such as a rhizome barrier or a concrete trench, around the planting area to contain the roots. 

Here's a more detailed explanation:

Choose the Right Barrier:
Opt for a barrier made of durable, high-density polyethylene (HDPE) that is resistant to degradation from soil and moisture. 

Install the Barrier:
Ensure the barrier is installed correctly, burying it deep enough to prevent rhizomes from traveling over or under it. 

Root Pruning:
Regularly cut or prune bamboo roots that are growing outside the designated area to prevent them from establishing new shoots. 

Remove Bamboo Rhizomes:
If bamboo has already spread, dig out the rhizomes and any new shoots to prevent further growth. 

Consider Herbicides:
While herbicides can be used, they may not always be effective, especially on established bamboo, and may require repeated applications. 

Choose Bamboo Wisely:
If you're planting bamboo, select a variety that is known for its slower spread, such as a clumping bamboo instead of a running bamboo. 

Regular Maintenance:
Regularly inspect the area around your bamboo plants and address any new growth or rhizomes as soon as they appear.