Oxydendrum arboreum also is referred to as sourwood, sorrel tree and lily-of-the-valley tree. They are indigenous trees to the southeastern United States. The fragrant, white flowers of the oxydendrum arboreum appear in spring and continue to bloom through early summer. Oxydendrum arboreum trees can grow to heights of 25 to 30 feet and are hardy in the USDA Zones 5 through 9. They grow best in full sun to light shade and prefer a rich, fertile soil. Planting Oxydendrum Arboreum SeedsFill a seed starting tray with sphagnum moss and vermiculite. Mist the surface of the soil until you are certain it is dampened well. Lightly scatter the oxydendrum arboreum seeds over the surface of the soil mixture. Try to keep the seeds between ½ and 1 inch apart. Sprinkle a light layer of soil over the seeds, approximately 1/16 of an inch. Place the tray of seeds into a plastic bag or cover them tightly with plastic wrap. Do not allow the plastic bag or wrap to come in contact with the growing medium. Place the covered tray 4 to 6 inches from a florescent light for 24 hours a day. The USDA Forest Service suggests using a cool-white fluorescent light. Keep the temperature between 65 and 70 F.Keep the soil in the tray moist. Spritz the surface of the growing medium every day or two, if necessary, so the soil is never allowed to dry out. Germination typically begins in two weeks. Open the plastic bag or loosen the plastic wrap to allow for ventilation when germination begins. Place the tray of seedlings into an irrigation tray and begin watering the seedlings from below. Pour water into the irrigation tray when the seedlings need moisture. Once seedlings have two to three sets of leaves or are about 2 to 2 ½ inches tall, transplant them into larger pots, such as peat pots, or 1-gallon pots. Transplanting Oxydendrum ArboreumFill peat pots or 1-gallon pots with a growing medium that contains peat moss. Pour water into each of the pots until you are certain the growing medium is well-moistened. Dig a hole in the center of each pot to a depth of about 3 to 4 inches. Use a spoon to gently dig out the oxydendrum arboreum seedlings from the tray. Transplant the largest and healthiest-appearing seedlings. Place an oxydendrum arboreum seedling in a pot. If the base of the stem is sitting lower than the surrounding soil, it's planted too deeply. Add or remove soil so that the seedling is sitting at the appropriate level to the surrounding soil. Scoop soil around the seedling with a spoon until the hole has been filled with soil. Tap down the soil around each of the oxydendrum arboreum seedlings. Water each of the oxydendrum arboreum seedlings with an indoor watering can. Place the pots 4 to 6 inches from the florescent lights. Give them 10 to 12 hours of light per day. Acclimate the seedlings to exterior temperatures when they are 6 months old.. Put them in a sheltered location for three to four hours a day for 10 to 14 days before planting them in the garden.