In the right environment, you can grow citrus trees of all kinds, including orange, lemon, lime, tangerine and grapefruit trees, at home. All citrus trees are attractive, with shiny green leaves, fragrant white flowers and tangy and colorful fruit. Outdoors, citrus trees prefer warm, humid environments, generally doing well in hardiness zones 9 or 10, the warmest U.S. regions. You can also grow citrus trees indoors as ornamental house plants, and they can even flower and bear fruit indoors under the right conditions. Except for seedless varieties, such as the naval orange, citrus fruits have seeds that you can germinate and plant.
Cut open a citrus fruit and remove the seeds or buy seeds from a garden center or seed catalog. If you removed the seeds from the fruit, rinse them with water and use them immediately.
Prepare a planting medium by mixing equal amounts of potting soil and coarse sand. Cut the drinking cups to about 3 inches tall and punch holes in the bottom for drainage. Fill the cups with the planting medium.
Plant the citrus seeds while they are still fresh and moist. Insert one seed a half-inch deep in each cup. Cover the seeds with potting medium and water lightly.
Place the each cup in a zip-top plastic bag and seal the bag. Put the cups in a warm place to germinate. Keep the soil damp but not wet.
Check the citrus seeds after a week or two for signs of growth. After the seeds sprout, remove the cups from the plastic bag. When the seedlings have three to four leaves on them, transplant each seedling to a 1-gallon container.
Ensure that the juvenile citrus trees receive about four hours of direct sunlight each day and temperatures remain between 60 and 70 degrees Fahrenheit.
Plant your tree outdoors by digging a hole twice as deep and wide as the root ball. Place the tree in the hole and back-fill. Do not to cover the trunk with soil.