How to Save Watermelon Seeds for More Plants Next Year

Sweet, juicy watermelons are a delightful addition to the table every summer. Learn how to save watermelon seeds for planting next spring.

How to Harvest Watermelon Seeds

Harvesting watermelons for seeds is simple, but it’s important to follow a certain procedure to ensure food safety:

1. Remove the melon: Cut the watermelon from the vine with shears or a sharp knife. Cut close to the stem but leave some of the stem on the melon.
2. Wash the melon: Gently scrub the watermelon with a vegetable brush under clean, running water. Do not use soap.
3. Dry the melon: Pat the melon dry with a cloth or paper towel. Hand-drying removes more bacteria from the rind than air-drying.
4. Remove the rind: Cut off each end of the melon, stand the melon upright, then cut away the rind. Use a sharp knife and cut along the melon’s curve.
5. Cut the melon: Cut the melon lengthwise into slabs, each slab about half an inch thick.
6. Pick out the melon seeds: Scrape out the melon seeds with a fork.

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How to Save Watermelon Seeds

Wash, dry, and store the watermelon seeds until the next planting season.

1. Remove the flesh: Remove as much of the watermelon flesh or pulp by hand.
2. Wash the seeds: Place the watermelon seeds in a kitchen colander or strainer and wash them with cool water. Remove all of the remaining watermelon flesh.
3. Dry the seeds: Air-dry the melon seeds on coated paper plates, waxed paper, or on clean mesh window screen material.
4. Store the seeds: Store the seeds in airtight, waterproof bags, jars, or containers in a cool, dark location.

When to Harvest Watermelons for Seeds

Harvest watermelon seeds when you harvest the watermelons for eating, usually in spring or summer. You can also harvest watermelons for seeds only, which affords a broader harvesting period.

Watermelons for Eating and Seeds

Watermelons should be harvested at just the right time. Watermelons do not ripen off the vine. If you harvest them too early, they will be watery and not sweet.

Signs that it’s time to harvest the watermelon seeds:

• Dry tendril: Dried curlicue on the vine closest to the watermelon
• Hollow sound: Resonant, hollow sound when gently rapped
• Heaviness: A heavy, dense feel when picked up
• Yellow underneath: A yellow (not white) oval under the melon, where it rests on the ground

Watermelons for Seeds Only

When harvesting watermelons only for their seeds, they can be harvested when ripe or left on the vine.

When reserving some melons on the vine, let the melons soften slightly but do not let them rot. Leaving seed-only melons on the vine can improve the quality of the seeds. Do not eat the melon’s flesh.

Types of Seeds to Plant

Harvest and save black watermelon seeds for planting. Do not use white seeds. Types of watermelons to plant include:

• Black Diamond: Popular for their enormous size, Black Diamond watermelons are juicy and sweet but require consistent watering.
• Charleston Grey: Modestly sized, Charleston Greys top the scales at around 40 pounds and have thick rinds often used for watermelon rind pickles.
• Crimson Sweet: Crimson Sweet watermelons grow easily in a wide range of melon-friendly climates, and the flesh is uniquely sweet. This melon produces few seeds, so more melons must be harvested to gather the seeds.

How to Plant Watermelon Seeds

Grow watermelons from seeds either by starting the seeds indoors in pots or flats or by planting the seeds directly in the ground. 

Watermelons need warm weather without intermittent cold spells, so plant the seeds after the last spring frost. In the U.S. south and southwest, the last spring freeze occurs as early as January. In western mountainous regions, it can be as late as May.

Watermelon seeds germinate fastest in soil that’s between 70 and 95°F. At the very least, the soil should be 65°F, and the seeds should be planted four inches deep.

Consult the USDA Plant Hardiness Zone Map to learn the optimal watermelon growing season for your area.