While hostas don't always grow true to the parent from seed, the surprise of what you may or may not get is worth the effort. Some gardeners choose not to propagate hostas from seed because they want a plant identical to the original plant, or they are under the misconception that hostas grown from seed are weak. For a plant identical to the original, propagating from seeds may not be ideal, but the grown plants will be just as hardy as any other as long as they are given proper care.
Gather seeds from existing plants when the seeds have turned black.
Fill one-quart planting pots with potting soil. Be sure to use pots that have holes in the bottom.
Tamp the soil down lightly.
Sprinkle the seeds evenly on top of the soil, placing 2-3 seeds per square inch.
Place a very thin layer of soil over the seeds, using just enough soil to cover the seeds.
Set the pots with the planted seeds in a tray filled about halfway full with water and let the water soak up through the potting soil until all of the soil in the pot is moist.
Remove the pots from the tray and place them in a warm, sunny location.
Cover the pots with plastic wrap or a clear plastic bag.
Wait for the seeds to germinate, checking the moisture level every few days to make sure the soil has not become dry.
Remove the plastic wrap after the seedlings have emerged.
Transplant the seedlings into individual pots, with fresh soil, when they have three to four leaves.
Harden the seedlings in the spring, about two weeks before planting, by leaving them outdoors during the day and bringing them in at night.
Plant the seedlings outdoors after the last frost.