You can easily start orange trees from seed. However, some varieties, such as the navel orange, have no seeds, and some varieties are hybrids, which will not reproduce "true to type." Heirloom oranges include Hamlin, pineapple orange and ambersweet. Orange trees you start from seed will take longer to produce fruit than young trees you purchase, but you can save a little money and learn a bit about how plants grow if you start this fruit from seed.
Starting Oranges From Seed
Collect seeds from a very ripe orange that is a known heirloom variety. Cut your orange into two pieces and then poke out the seeds with a fork or a knife. Wash the pulp from the seeds by running them under room-temperature water and then lightly rub each seed with your fingers.
Set a screen, such as a window screen, on bricks or pieces of wood in a warm, dark, dry, well-ventilated area such as your garage. Leave them on the screen for about 10 days and then remove seeds when they are dry.
Mix together about one quart of potting soil with ½ cup each of vermiculite, sand and peat moss. Fill a flat with this mixture, sprinkle it with water and then make holes ½ inch deep and 1 inch apart. Insert one seed into each hole, cover them with your potting mixture and then cover the flat with plastic wrap. With the point of a paring knife, make holes in the plastic wrap to prevent the temperature from rising too high.
Keep your flat in a sunny spot that is not too hot--the temperature necessary for orange seeds to germinate is around 70 degrees Fahrenheit. Every day, remove the plastic wrap and water your flat well. When you see seedlings emerging above the soil line, remove the plastic wrap.
Transplant your orange seedlings to one-gallon nursery pots when they are 2 to 3 inches tall---this should take approximately three months. Use a slightly acidic potting soil and place your pots in an area that receives maximum sun. Water well when you first transplant your orange seedlings and then water them once each week until they are about 1 foot tall and old enough for you to plant them in a permanent outdoor location. Wait until after your final spring frost because young orange trees can suffer frost damage.