To propagate fountain grass, the most reliable method is by dividing an established clump in early spring, after cutting back last year’s growth, using a sharp tool to separate sections with healthy roots and replanting them immediately; this also rejuvenates the original plant; while you can technically grow fountain grass from seed, it’s not always reliable as cultivated varieties may not come true from seed. 

Key points about propagating fountain grass:

Best time to divide: Early spring, after cutting back old foliage. 

Method: Dig up the plant, carefully separate the clump into smaller sections with attached roots, and plant the divisions in new locations. 

Seed propagation: While possible, not always recommended as seed might not produce plants identical to the parent plant. 

Important considerations:

Use a sharp tool to avoid damaging the roots. 

Ensure each division has healthy roots.  Water the newly planted divisions thoroughly.