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Watermelon Seed Starting Tips

Watermelon seed can be started indoors 8 to 6 weeks before plants are set out.
Watermelon seedling
Watermelon seedling

Watermelons are a tender, warm-weather crop.

  • Sow watermelon seed or set plants directly in the garden in spring 2 weeks after all danger of frost has passed after the soil has warmed to 70°F (21°C).
  • Watermelon seed can be started indoors 8 to 6 weeks before plants are set out.
  • For the sweetest flavor, watermelons require a long, hot growing season and plenty of room; watermelon vines require 10 to 15 feet of grow room.

Watermelons mature 70 to 100 frost-free days after sowing depending on the variety.

Sowing and Planting Tips:

  • Grow watermelons from seeds or seedlings.
  • Seed is viable for 4 to 5 years.
  • Start watermelon seed indoors 8 to 6 weeks before transplanting seedlings to the garden; set out transplants 2 or more weeks after the last frost in spring.
  • Sow seed indoors in peat pots filled with seed starting mix. The indoor temperature should be between 80-90°F (27-32°C) until germination. Grow watermelon seedlings at 75°F (24°C).
  • Direct sow watermelons in the garden in spring after all danger of frost has passed and the soil has warmed to 70°F (21°C). In warm-winter regions, sow watermelons in midwinter for harvest in early summer.
  • Watermelon seeds will not germinate at a soil temperature below 65°F (18°C).
  • Sow seed ½ inch (13 mm) deep.
  • Seeds germinate in 3 to 10 days at 80°F (27°C) or warmer.
  • Transplant seedlings to the garden after the soil has warmed to at least 70°F (21°C).
  • Plant on mounds or hills 12 to 24 inches (30-60 cm) high, space mounds 10 feet apart; vines can easily spread 10 to 15 feet.
  • Water to keep the soil from drying.
  • Fertilize with fish emulsion or a soluble complete fertilizer at half strength.
  • Add aged compost to planting beds in advance of transplanting.
  • Watermelons prefer a soil pH range of 7.0 to 8.0.
  • Grow watermelons in full sun for best yield.
  • Avoid planting watermelons where cucumbers or squash have grown recently.
  • Common pest enemies include aphids, cucumber beetles, flea beetles, squash bugs, squash vine borers, slugs, and snails.
  • Common diseases include bacterial wilt, fusarium wilt, downy mildew, powdery mildew, cucumber mosaic.

Interplanting: Plant watermelons with bush beans, corn, dill, eggplant, lettuce, cucumbers, squash, and tomatoes.

Container Growing Watermelon: Watermelons are not a good choice for container growing. They require significant room to spread and grow.

Watermelon Planting Calendar

  • 8-6 weeks before the last frost in spring: start seed indoors for plants that will be transplanted into a plastic tunnel in 4 weeks.
  • 5-4 weeks before the last frost in spring: start seed indoors for seedlings to be transplanted into the garden.
  • 4-2 weeks before the last frost in spring: transplant seedlings to a plastic tunnel.
  • 1-2 weeks after the last frost in spring: direct sow or transplant seedlings into the garden; minimum soil temperature is 60°F.
Watermelon plant
Watermelon seed can be started indoors 8 to 6 weeks before plants are set out.

Recommended Watermelon Varieties

  • ‘Sugar Baby’ and ‘Sugar Bush’ are small, 8-10 pounds.
  • ‘Fiesta’, ‘Regency’, and ‘Sangria’ are 20 to 25 pounds—all are very sweet.

Botanical Name: Citrullus lanatus var. lanatus

Melons are a member of the Cucurbitaceae family; other members cucumbers, squash, watermelon, and pumpkins.

More tips: How to Grow Watermelon.

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29 Comments

    • Watermelon fruit can separate from the vine for several reasons: (1) check to make sure an animal is visiting the garden and feeding on plants; (2) young watermelons can be attacked by insects which can cause separation of the young fruit from the vine; look carefully for insects and treat with insecticidal soap or neem oil spray; (3) water stress; make sure the soil does not dry out–keep the soil evenly moist; (4) stress caused by very high or very low temperatures; (5) incomplete pollination; the flower was not fully pollinated; encourage bees and other pollinators by planting flowers nearby. Here is a link to Melon Troubleshooting article:
      https://harvesttotable.com/?s=melon+troubleshooting

  1. I need some clarification. Above you say, Avoid planting watermelons where cucumbers or squash have grown recently. But then under Interplanting: Plant watermelons with bush beans, corn, dill, eggplant, lettuce, cucumbers, squash, and tomatoes. They can grow with cucumbers? But not after? Because of heavy feeding? Or ?? Also, I’d like to know if what I’m finding on your website is in your book that I’m buying from Amazon. I’m taking copious notes, but hoping I will be able to just pull the book off the shelf for reference instead of having to keep running back and forth to my computer. Thank you for sharing so much helpful info!

    • First, look for my new book The Vegetable Garden Grower’s Guide which will be out in the early summer of 2018; that book may be the reference you need. You can plant watermelons alongside heavy feeders such as cucumbers, squash, and tomatoes, but you do now want plant watermelon after those crops–they are all heavy feeders and will use many nutrients in the soil. After growing heavy feeders you want you want to feed the soil with aged compost and aged manure or plant a cover crop of beans to feed the soil–that is to renew nutrients.

    • A likely cause would be too much water close to harvest time; cut back on water about 10 days before harvest. As the melon reaches mature size and a yellow spot develops where the melon touches the ground, you will know harvest is coming. Water is important as the melon develops but once it is near ripe, too much water will dilute the melon’s natural sugars and cause the flesh to be mealy. As you prepare for the new season, add 2 or 3 inches of aged compost or a commercial organic planting mix to the soil and turn it under to about 8 inches. You can never add too much organic matter; aged compost will be rich in nutrients and make the soil well drained at the same time.

    • Choose a watermelon variety that comes to harvest in 70 to 85 days; these are short-season varieties. Plant where the melons will get 70 days of temperatures between 70-80F/21-26C or warmer. Place aluminum foil or bright metal under the small melons so that they can soak up as much solar heat as possible.

    • Aged compost contains both major and minor nutrients that are slowly released in the soil. If your soil is humus-rich or if you have added aged compost to the soil, additional fertilizer is not needed. If you believe the soil is nutrient deficient get an organic slow-release fertilizer lower in nitrogen and higher in phosphorus — such as 5-10-10.

  2. My watermelon seedlings have just popped out of the ground and a few is them have the seed casing still on the new leaves. Should I gently pull that off?

  3. Can you tell me what a yellow fleshed watermelon is called? I just got some seeds in Texas and I’m planting them in Arkansas. I used to have them as a kid. Is there anything I need to do different for them?

    • Yellow flesh in a watermelon is a natural mutation. Yellow-fleshed watermelons are grown the same as all other watermelons. There are several yellow/orange-flesh watermelon varieties including Desert King, Janosik, Kaho, Leelanau. Lemondrop, Mountain Sweet Yellow, Moon and Stars, Yellow Doll, Yellow Buttercup, Yellow Petite, and Yellow Crimson.

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