Remove the seeds from a fresh grapefruit. Wash the seeds under running water and pat them dry with a towel.
Fill a 4-inch pot three-fourths full with a rich potting mix that drains well.
Under ideal conditions the grapefruit seedling may flower and produce fruit in six to seven years.
How to Plant Grapefruit Seed
A south-facing window covered with sheer curtains provides sufficient light without exposing the seedling to direct sunlight, which may burn the plant.
Press one grapefruit seed into the center of the pot. Push the seed into the soil so it is twice as deep as the seed is long. For example, if the seed is 1/4 inch long, plant the seed 1/2 inch deep.
Water the newly planted seed until the soil is moist but not soggy. Cover the pot loosely with plastic wrap to create a greenhouse effect to keep the seed warm and encourage growth.
Transplant the seedling to larger pots, such as 6-, 8- and 12-inch containers, as it grows so the roots will have plenty of room.
Place the covered pot in a brightly lit, warm location with a consistent temperature of around 70 degrees Fahrenheit. Monitor the progress of the plant, adding water as necessary to keep the soil moist. Watch for the seed to sprout and leaves to form.
You can grow your own grapefruit tree from seed harvested from your breakfast fruit. Plant the seed and keep it warm so it germinates indoors.
Grapefruit seeds go dormant if they dry out. Soak them in clean, room temperature water for 24 hours before sowing to revive them.
Transplant all of the sprouted seedlings into individual 3- to 4-inch pots filled with sterile soilless growing medium once they produce several sets of leaves. Be sure to plant them at the same depth as they were in their starter pots. Use pots that have drainage holes.
All varieties of grapefruit grow in U.S. Department of Agriculture plant hardiness zones 9 through 11, although most cultivars will also grow in zone 8b once established.
Keep the soil evenly moist, but let the surface dry out between waterings to reduce the risk for root diseases. Water until the excess drains from the bottom of the pot.
Fill the pot to within a 1/2 inch of the top with sterile, soilless potting medium, or create your own by combining equal parts milled peat moss and half perlite or medium-grain sand. Saturate the mix with water and let the excess drain off for 15 minutes before sowing.
Wash a small plastic pot that has multiple drainage holes around the base. Size doesn’t matter, although smaller, 2- to 3-inch pots warm up more easily. Dry the inside with a clean cloth.
Transplant the grapefruit seedlings into half-barrel containers or into the ground in spring of their third year. Position them in a bright, sunny spot and fast drainage.
Move the pots outdoors to a sheltered area with bright, diffuse light in spring of their second year. Keep them watered as before, and feed every two weeks with 1/2 teaspoon of water-soluble, 10-10-10 fertilizer diluted in 1 gallon of water. If yellow leaves appear, reduce feeding frequency by half.
Cover the seeds completely with soil to block out the light. Loosely drape a sheet of plastic wrap over the pot and move it to a warm spot where temperatures stay between 70 and 80 degrees Fahrenheit. A propagation mat works well, but the pot will stay just as warm on top of a refrigerator.
Grapefruit trees sprout easily from seeds, although the seedlings lack the same fruit quality as commercially grown trees.