Grapefruits (Citrus x paradisi) stand out among other citrus varieties with their large size and mouth-puckering fruit, which contains anywhere from zero to more than 60 seeds. Fresh grapefruit seeds sprout readily and can be used to grow a tree, although seed-grown trees lack some of the advantages of grapefruit trees from a garden center.
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Types of Grapefruit
Grapefruits fall into two categories: white-fleshed and red-fleshed. Common white-fleshed varieties include the 'Duncan' grapefruit (Citrus x paradisi 'Duncan'), which is a seedy variety with 30 to 50 seeds in each fruit. Red-fleshed varieties include 'Ruby' (Citrus x paradisi 'Ruby'), which is a common grapefruit at supermarkets. 'Ruby' is a seedless variety, which means it has six seeds or fewer per fruit.
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.
Seed-Grown vs. Grafted
Grapefruit trees are typically propagated with bud grafting to increase their resilience and hasten fruiting. Seed-grown grapefruit trees often prove less reliable than their nursery-grown counterparts, and may include drawbacks such as:
- Delayed fruiting. Seed-grown grapefruit trees can take four to five years to flower or fruit. In extreme cases, flowering and fruiting can take up to 15 years.
- Shorter life span. Grapefruit seedlings are often short-lived. Disease, cold and drought kill seedling more easily than grafted trees.
- Strange fruit. Grapefruit seeds are polyembryonic which allows them to grow true to type. But mutations can create seedlings of varying quality. Plant more seeds than you plan to use so you can choose the strongest.
Grapefruit seedlings with undesirable fruit can still be enjoyed for their highly fragrant, waxy white flowers.
Preparing Grapefruit Seeds for Planting
Grapefruit seeds do not require extensive preparation, although the seeds must be sown fresh. Have your pots prepared before you open the grapefruit up. Rinse the seeds in clean water after removing them from the fruit to get rid of the sugary residue, then pat them dry on a paper towel. Do not let the seeds dry out completely.
Seeds taken from ripe fruit perform best, so only collect seeds from grapefruits with a solid, pure gold skin with no hint of green at the ends.
Grapefruit seeds go dormant if they dry out. Soak them in clean, room temperature water for 24 hours before sowing to revive them.
How to Sow and Germinate Grapefruit
Grapefruit seeds can be started any time of year, although they perform best when started in spring as the days lengthen and the weather warms.
Step 1: Prepare the Planting Pot
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.
Step 2: Create the Potting Mix
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.
Step 3: Sow the Grapefruit Seeds
Sow three grapefruit seeds in the pot. Sow the seeds at equal distance from one another at a depth equal to twice their length. For example, a 1/8-inch-long grapefruit seed should be sown at a depth of 1/4 inch, while a 1/4-inch-long seed should be sown 1/2 inch deep.
Step 4: Choose a Warm Spot
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.
Step 5: Watering the Seeds
Step 6: Watch for the Seedlings
Watch for the first grapefruit seedlings in two to three weeks. Remove the plastic after they emerge, and move the pot to a bright, sunny spot indoors near a lightly shaded south-facing window.
How to Transplant Grapefruit Seedlings
Grapefruit seedlings grow slowly, but they still need the right conditions and plenty of space to spread out as they mature.
Step 1: Transplant the Seedlings
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.
Step 2: Set the Pots in a Bright Window
Position the pots near a south- or west-facing window with roughly four hours of direct sunlight each day. Maintain temperatures between 60 and 70 F. In winter, temperatures must stay above 40 F.
Step 3: Keep the Soil Moist
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.
Step 4: Repot the Seedlings
Repot the grapefruit seedlings in spring into a pot that is no more than 1 to 2 inches larger than the previous pot. Use soilless medium and a pot that has multiple drainage holes around the base.
Step 5: Move the Pots Outdoors
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.
Step 6: Transplant the Seedlings
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.
Grapefruit trees are thorny, so plant them away from areas where pets and children play.
- Floridata: Citrus x Paradi
- Texas A & M Department of Horticulture: Home Fruit Production-Grapefruit
- University of Vermont Extension: Growing Citrus as Houseplants
- California Rare Fruit Growers: Growing Rare Fruit from Seed
- University of California Cooperative Extension: Citrus
- Logee's Plants for Home and Garden: Cultural Information--Citrus
- Purdue University Center for New Crops and Plants Products: Grapefruit