Gardeners often save seeds from a particularly sweet or flavorful watermelon purchased from the store, hoping to reproduce a favorite fruit. The short answer to whether you can replant watermelon seeds from a fruit is yes, you absolutely can, but the result you harvest may not look or taste exactly like the parent melon. Understanding the genetic background of the seed is the most important factor determining your success.
Understanding Seed Genetics
The vast majority of watermelons sold in grocery stores are grown from hybrid seeds, labeled F1, which stands for “First Filial Generation.” These F1 seeds are the result of a deliberate cross between two distinct parent lines, chosen for desirable traits like high yield, disease resistance, and uniform size. This hybridization process results in hybrid vigor, where the first generation plants exhibit superior performance.
The problem arises when you save seeds from this F1 hybrid fruit and plant them, creating the F2 generation. These F2 seeds do not “breed true” because the genetic combination breaks apart and recombines randomly in the offspring. The resulting F2 watermelons can exhibit a wide and unpredictable range of traits, often reverting to less desirable characteristics of the original grandparents.
This genetic instability means you might grow a plant that produces small, bland, or oddly shaped fruit, or a melon with a different color or texture. True success in seed-saving is reserved for open-pollinated varieties, which include heirloom watermelons. Open-pollinated seeds produce plants that are true-to-type, meaning the offspring will reliably possess the same characteristics as the parent fruit.
Preparing Seeds for Germination
Once you have secured your seeds, preparation is necessary to ensure successful germination and prevent mold. Watermelon seeds are encased in a sugary pulp that contains germination inhibitors, which must be removed. Scooping the seeds and pulp into a container of water and letting them sit for two to three days facilitates this removal.
During this time, a slight fermentation occurs, which helps to break down the sticky, sugary coating. Viable seeds will typically sink to the bottom of the container. Non-viable seeds or excess pulp will float and should be skimmed off and discarded. Afterward, the seeds must be thoroughly rinsed under cool water to remove all remaining debris.
Proper drying is important to prevent rot and ensure long-term viability. The cleaned seeds should be spread out in a single layer on a paper towel or newspaper in a location with good air circulation, away from direct sunlight. Allow the seeds to dry completely for a week or two until they are hard and brittle before being stored in an airtight container in a cool, dark, and dry place.
Planting and Early Seedling Care
Watermelon seeds thrive in warmth and should only be planted once the soil temperature is consistently high. For direct sowing outdoors, the soil temperature should be at least 65°F. Germination is fastest when the soil is between 70°F and 95°F. Planting too early in cold soil risks seed rot and poor germination.
To get a head start, you can begin seeds indoors four to six weeks before the last expected frost. Plant the seeds about a half-inch to one inch deep in small containers. Ideally, use biodegradable peat pots to minimize root disturbance during transplanting. Watermelons have sensitive roots, and moving them from the pot to the ground must be done gently.
Keep the seed-starting mix moist but not saturated, as excessive water can lead to seed death. Once the seedlings have developed two or three true leaves, they must be gradually hardened off before being moved outside permanently. This process involves slowly introducing the young plants to outdoor conditions, like sunlight and wind, over the course of about a week.