Growing Seedless Watermelons in 5 Steps
Can I Grow Seedless Watermelons?
While growing seedless watermelon is possible, it does take dedication and effort. Seedless watermelon seeds are expensive (about 10 to 15 cents each) and need special growth environments for best results. Follow these five steps for success.
Learn About Seedless Watermelon
Seedless watermelons, quite simply, develop fruit but no seeds because they are sterile. The sterility is caused by crossing plants that are incompatible genetically.
Many people are taken aback when they slice a “seedless” watermelon and see what they think are tiny, white seeds. Actually, these rudimentary (undeveloped) seed coats are edible, just like the seeds in cucumbers.
Most experts, like Laurie Hodges at the University of Nebraska1, recommend starting them from seeds and transplanting them rather than sowing them directly into the garden. Here is what we did to get our seedless watermelons off to the best start.
What You Need
Here is what you will need to start your seedlings and harden them off:
- Seedless watermelon seeds
- Seeded watermelon seeds (choose a variety with a different colored rind than the seedless so you can easily distinguish the two types)
- Peat pots or eggshell planters (see note below)
- Growth medium or fertilizer mix
You need both types of seeds or plants, as seedless watermelon does not produce enough pollen to set fruit. The seeded watermelon, sometimes called the pollinator cultivar, provides the supplemental pollen. The best anthracnose resistant varieties of seedless watermelons are Crimson Sweet, You Sweet Thing Hybrid, or Summer Sweet 5032.
Author's note: This year, we are experimenting with starting the seeds in eggshells as part of our ongoing method of teaching our son to garden. We plan to put the seedless type in white eggshells and the seeded ones in brown eggshells to make it easier to tell them apart. We'll plant the entire thing and as the eggshell decomposes, it will feed our baby seedlings naturally.
Use Eggshells as Organic Planters
Step 1: Start the Watermelon Seeds
- Use peat pots and a greenhouse-type growth medium that includes a fertilizer charge. Prepare the pots by filling them with the growth medium and moistening the soil until the excess water runs off.
- The pots must be kept warm (85 degrees Fahrenheit) for 48 hours to warm the soil in preparation for the seeds. (Seedless watermelons cannot tolerate the cold.)
- Plant the seeds at a depth of one inch. Plant the tip of the seed at a 45 to 90-degree angle to prevent the seed coat from adhering to the cotyledon. Cover them with moist soil and keep warm (85 degrees Fahrenheit) for 48 hours, and then move them to a cooler environment for germination and seedling development.
Step 2: Germination Tips
- The seeds need to be kept at temperatures between 72 and 75 degrees Fahrenheit during the day and no colder than 65 degrees Fahrenheit at night. Wait until the seedlings emerge before watering, and be careful not to over water.
- Seedless watermelons need a slow germination period at relatively cool temperatures and limited irrigation for the best results.
- The fertilizer charge in the growth medium should provide enough nutrition during this stage, but fertilize with a 100 ppm nitrogen concentration at two other stages: the appearance of the first true leaf, and second true leaf.
- Seedling development takes about four to six weeks.
Seedless Watermelon versus Seeded Watermelon
Step 3: Hardening Off the Seedlings
Prepare the plants about seven days prior to their transplant to the garden (also known as hardening off the plants.)
Lower the temperature where they are during the day or set the plants outside. Bring them in each night. Water sparingly, if at all.
Step 4: Prepare the Garden Patch
- For the best pollination results, plan a garden layout that allows you to “plant the pollenizer variety in the outside row and then every third row.”2
- If you are growing watermelon in a small garden plot, try alternating seedless and seeded plants in a row, but remember that the two plants must be close for pollination purposes.
- See screenshot of chart above for ideas on how to plant the seedlings to get the highest yields.
Step 5: Transplanting & Growing Seedless Watermelon
Follow these simple steps for a bumper crop of juicy, sweet seedless watermelons:
- Transplant the seedlings after the last frost date for your area.
- Place seedlings about four feet apart in rich, loamy soil. If you want to skip weeding, lay down a layer of black plastic before planting to kill the weeds.
- Water daily until the fruit appears, and then water only when the soil is dry.
- Fertilize with a 5-10-10 mixture as needed.
- Handle the fruit as little as possible during the growing season or the flesh will be bland and tasteless. The fruit is ripe when the rind resists the pressure of a fingernail.
Although the seeded melons are easier to germinate and do not require as much special attention to germinate, it makes sense to save time and effort by starting the seeds simultaneously. As long as both types are ready to transplant at the same time, there is no harm done by starting them at the same time.
Inspect plants frequently to avoid losing your crop to typical problems such as anthracnose or gummy stem blight.
References and Sources
1 Hodges, Laura, “Growing Seedless Watermelon,” NebGuide.
2 Maynard, Donald N., “Growing Seedless Watermelon.”
Johnson, Gordon, “Producing Quality Seedless Watermelon Transplants.”
Ortho's Home Gardener's Problem Solvers, Michael McKinley, editor.
Rodale's Complete Garden Problem Solver, Delilah Smittle, editor.
Questions & Answers
© 2011 Donna Cosmato