How to Start Hosta Seeds
Hostas can easily be started by seed and will produce a new plant seedling in a matter of weeks. However, when hostas are propagated by seed they very rarely produce a new plant that is an exact replica of the plant from which the seed was taken. This makes growing hosta from seed a bit of a surprise process in that a healthy plant will result but you will not know the varietal until the foliage begins to appear. One varietal, hosta ventricosa, is an exception to this as it will produce an exact replica plant when started from seed. Hosta are most commonly propagated by dividing the plants in the spring or fall and replanting the divisions. Hosta seeds should be started indoors in the late winter or spring.
Prepare nursery pots or flats filled 3/4 of the way to the top with a commercially bagged, nutrient-rich, organic potting soil that is sterile and drains easily.
Plant your hosta seeds approximately a 1/4 to 1/2 inch deep in the potting soil. Space the seeds at a rate of one to two seeds per square inch or thereabouts. Cover lightly with the potting medium without compressing the soil onto the seeds. Watering the seeds will ensure good contact between the seeds and soil, so compacting the soil at planting is not recommended.
Water in the hosta seeds deeply and carefully so as not to disturb the soil. Keep the soil evenly and consistently moist throughout the germination and seedling stages, never allowing the soil to dry out.
Cover the pots or flats with a clear plastic cover to create a greenhouse effect. Keep the seeds covered until the seedlings each posses at least one fully formed small leaf. The cover can then gradually be removed for more hours each day to slowly acclimate the tender young plants to their surroundings. Crack or lift the cover if you see mold forming on the seeds or soil, and cut back a bit on watering.
Transplant hosta seedlings only after they are four to five inches in height and have developed a half-dozen leaves or more each. Transplant your hostas out into the garden soil in the late spring after the last frost is well passed or in the summer or fall at least six weeks before the first frost. Waiting to transplant until a later season is perfectly acceptable if your seedling pots are large enough to hold the maturing roots or the seedlings can be carefully transplanted to larger pots.