Goldenrod can be propagated by division or by seed.
Division
When to divide: Divide in the spring before new growth starts, or in the fall.
Prepare the plant: Water the plant a few days before to hydrate the roots.
Dig up the plant: Use a shovel to dig around the root ball and lift the clump out of the ground.
Separate the clump: Use a sharp knife or spade to cut the clump into smaller sections, each with a few growth tips.
Replant: Place each section back into the ground at the same depth as the original plant.
Water and maintain: Water well and continue to water until new growth appears.
Seed propagation
Prepare the seeds: Sow seeds indoors in small pots or flats filled with potting mix.
Provide light and warmth: Place the pots in a warm location with full sun or a grow lamp, and keep the temperature between 80–86°F.
Water and maintain: Mist the seeds daily to keep them moist, but not soggy.
Thin seedlings: Once the seedlings have a few sets of true leaves, thin them to two plants per pot.
Harden off: Place the seedlings outdoors in a protected location for a short time, gradually increasing their exposure to sunlight, wind, and cold temperatures.
Transplant: Transplant the seedlings outdoors after the last spring frost, 12–18 inches apart.