To propagate Helenium, the most common method is to divide established plants in either spring or autumn by digging up the clump and carefully separating it into smaller sections with a sharp spade, then replanting the divisions in a new location; this is considered the quickest way to get new Helenium plants and is also a good practice to maintain the vigor of existing clumps every few years. 

Key points about propagating Helenium:

Division is the preferred method: Most gardeners propagate Helenium by dividing existing plants as they naturally form dense clumps. 

When to divide: The best time to divide Helenium is either in early spring after new growth starts or in autumn when the plant is dormant. 

How to divide: Dig up the entire plant clump. 

Use a sharp spade to cut through the root ball, separating it into smaller sections with healthy roots and shoots.  Discard any old or damaged parts.  Replant the divisions in a new location at the same depth as the original plant.  Water well until established. 

Other methods (less common):

Seed propagation: You can also propagate Helenium from seed, but this can be less reliable as some varieties may not come true to type. 

Sow seeds directly outdoors after the last frost or start them indoors earlier. 

Note that seeds may require cold stratification before germination. 

Cuttings: In theory, you can take basal cuttings from young shoots in spring and root them under cover, but this is not a widely practiced method.