Fatsia japonica, or Japanese aralia, charms gardeners with its large, lobed leaves and sprawling growth habit since it adds a dramatic element to ornamental landscaping. The shrubs grow effortlessly from seed and eventually reach a mature height of 6 to 10 feet if planted in a partially shaded bed with fertile soil and some protection from strong winds. The seeds, however, must be sown fresh and kept warm, moist and near bright light to prompt reliable germination.
Harvest a cluster of fruit from a mature Fatsia japonica shrub in autumn when the flesh turns blackish-purple and the individual fruit feels soft when pressed.
Place the fruit in a bowl of room temperature water. Crush the fruit between your fingers to loosen the flesh. Soak the fruit for 24 hours. Pour the bowl into a mesh colander. Pick out the small, pointed seeds.
Sow the Fatsia japonica seeds in 3 1/2-inch starter pots filled with equal parts potting soil, compost and medium-grit sand. Sow one seed in each pot to a depth of 1 inch. Pour 6 or 7 tbsp. of water into each pot.
Arrange the starter pots on top of a propagation warming mat near a large window with full sun exposure for six to eight hours each day. Drape plastic wrap over the starter pots to hold moisture and heat around the seeds. Set the propagation warming mat to 80 F.
Water each starter pot with 6 or 7 tbsp. of water whenever the soil feels dry 1/4 inch below the surface, which happens approximately every three to five days. Maintain moisture at this level before, during and after germination.
Watch for germination within two to four weeks. Remove the plastic wrap as soon as the seedlings emerge. Keep the starter pots on the propagation warming mat for one to two weeks after the seedlings emerge.
Transplant the Fatsia japonica seedlings into 8-inch-deep plastic pots filled with potting soil as soon as they reach 3 inches in height. Keep the young plants in a warm, sheltered spot until soil temperatures reach 70 F, then plant them in a partially shaded bed with fertile soil.