To propagate lungwort, the most common method is to divide established clumps of the plant after flowering in the spring or early fall; carefully dig up the root ball, gently separate it into smaller sections with roots attached, and replant each division in a new location, ensuring each section has at least a few shoots for proper growth. 

Key points about propagating lungwort:

Division is preferred: Most modern lungwort varieties are hybrids, so propagating from seed is not recommended as the seedlings may not be true to the parent plant. 

Timing: The best time to divide lungwort is after flowering in the spring. 

Process: Dig up the entire plant carefully. 

Gently separate the root ball into smaller sections using your hands or a sharp knife.  Discard any woody or non-viable parts.  Replant the divisions at the same depth as the original plant and water thoroughly.