Although some impatiens varieties can be grown in sun, the shade-loving varieties add a blast of color to a drab garden. The impatiens can be grown indoors or outdoors and in planters and hanging baskets. Planted in masses, you can create a carpet of multicolored impatiens in the garden. The annual variety is easier to grow from seed, so choose the appropriate annual seed for your specific growing conditions. Start germinating your impatiens seeds eight to 10 weeks prior to the last frost. The first flowers should bloom within eight to 10 weeks of sowing the seed.
Fill a seed tray with seed-starting potting soil. Water the soil well and allow it to drain.
Sow impatiens seeds on the surface of the soil. They need light in order to sprout, so don't cover the seeds.
Place the seed tray inside the plastic bag and secure it. Place the tray on top of the heating mat, set at 75 degrees F, and move it to a room that receives plenty of light.
Germination should occur within two weeks. When the seeds sprout, remove the tray from the plastic bag.
Remove the tray from the heat mat when the seedlings have their first set of leaves and plant in small planting pots with adequate drainage. Keep them moist but not soggy.
Harden off the impatiens seedlings after the last frost. Hardening off is a method of gradually introducing the plants to the outdoor environment. Move the seedlings to a protected area of the garden and leave them there for three hours a day. After 3 days, begin to lengthen the period that the seedlings are left outside. In 10 days the seedlings should be hardy enough to be planted in the garden.