Grapefruit trees can survive indoors or outdoors. Rather than purchasing a grapefruit tree, save money by harvesting grapefruit seeds from store-bought grapefruit. The seeds germinate easily when started indoors, and the trees produce delicious fruit in as little as one year.
Slice the grapefruit open with a sharp knife. Choose a variety of grapefruit that you would like to grow.
Remove the seeds with your fingers. Pick out the largest seeds and set them off to the side.
Wash the seeds under warm water. Place them on a layer of three moist paper towels. Fold the paper towels over in half. Continue to fold the paper towels to cover the seeds with a thick layer.
Keep the paper towels moist. Place them in a warm location where they will not dry out too quickly. Transplant the seeds once they begin to sprout leaves and roots.
Fill a paper cup with soil. Plant one germinated seed into the cup at least 1 inch into the soil.
Water the soil to keep it moist. Place the cup in a warm location that maintains a temperature between 21.1 and 29.4 degrees Celsius. Allow the grapefruit seed to germinate. This may take anywhere from one week to a month. Keep the soil moist and poke two holes in the bottom of the cup to allow the water to drain.
Transplant the grapefruit once it becomes too large for the cup. You will need a container twice the size. Keep it in a sunny and warm location.
Move the tree outdoors. Once the tree reaches 2 to 3 feet in height, plant the grapefruit tree outside next to concrete or a south-facing wall where the heat will reflect.
Dig a hole at least 3 to 5 feet in diameter with a shovel. The hole needs to be wider than the root ball but at the same depth. Create a watering ring around the grapefruit tree about 5 to 6 inches in height, and wider than the planting hole.
Water the tree every seven to 10 days deeply. Do not water the tree when it rains, and prevent over watering the tree when the weather cools.
Add 2 to 3 inches of mulch around the tree to help it retain water.
Fertilise the grapefruit tree every four to six weeks during the growing season between March and August.
Trees may not produce fruit for three years. Be patient when growing any type of citrus tree. Grapefruit seeds can only survive in areas that do not reach temperatures lower than -1.11 degrees C.