How to Grow Watermelon from Seed: A Complete Guide

Watermelon (Citrullus lanatus) is the classic taste of summer, and growing it from seed is easier than many gardeners expect. Watermelon thrives in hot, humid weather and sandy, well-drained soil, and it rewards a little care with big, juicy fruits. Starting your own seeds also lets you choose from far more varieties than you will find as nursery transplants. With a head start indoors and the right watering at each stage, you can harvest sweet, homegrown melons by mid to late summer. Shop watermelon seeds

Watermelon growing at a glance

  • Botanical name: Citrullus lanatus
  • Need for sun: 8+ hours (full sun)
  • Planting depth: 1/2″–1″
  • Sprouts in: 5–10 days
  • Ideal growing temperature: 70–90°F
  • Minimum soil temperature for direct sowing: 70°F
  • Plant spacing: 3–4 ft
  • Frost hardy: No
  • Growth habit: Vining

When to Start Watermelon Seeds

Start watermelon seeds indoors 3–4 weeks before your last frost date. Watermelon grows quickly, so a short head start indoors is all it needs to be ready for the garden once the weather warms. You can also sow seeds directly in the ground after your last frost, as long as the soil has warmed to over 70°F.

How to Start Watermelon Seeds Indoors

  1. Fill seedling trays or small seedling pots with a seed starting soil that has essential nutrients in it.
  2. Sow seeds 1/2″–1″ deep and cover them with soil.
  3. Keep the soil moist for quick germination. In warm conditions, seeds should sprout in 5–10 days.
  4. Keep the young seedlings under good light. Strong light gives you strong plants with sturdy, healthy stems and leaves instead of tall, weak seedlings.

When to Transplant Watermelon

Transplant watermelon seedlings to the garden, or to a pot with ample space for roots to spread, after your last frost. Watermelon is not frost hardy and grows best at 70–90°F, so wait until both the air and the soil are warm. Handle the root ball gently when transplanting, since watermelon roots don’t like to be disturbed.

How to Direct Sow Watermelon Seeds

Alternatively, you can direct sow watermelon seeds in the ground after your last frost. Note that seeds can rot when they are direct seeded if the soil is cool and moist before they can sprout, so make sure the soil temperature is over 70°F before you sow. A soil thermometer takes the guesswork out of timing.

Best Soil and Spacing for Watermelon

Watermelon does best in sandy soil with good drainage. Plant in fertile soil in a spot that gets at least 8 hours of full sun a day. Space plants 3–4 ft apart so the vines have room to spread and air can circulate between them.

How to Fertilize Watermelon

Feed watermelon plants with a liquid fertilizer once every two weeks. Regular feeding keeps the vines growing vigorously and supports flowering and fruit development.

How to Water Watermelon

Water regularly, especially during the flower stage, when the plants need steady moisture to set fruit. Once the fruits are maturing, reduce watering to improve flavor and sugar content. Always water at the base of the plant rather than over the leaves, and mulch around the plants. Both habits keep the foliage dry and help minimize disease.

Trellising Watermelon

If your watermelon variety produces small fruits, you can grow the plants on a trellis. Trellising lifts the vines off the ground, which improves air circulation and decreases disease pressure. It also saves a lot of garden space.

Watermelon Growing FAQ

How long do watermelon seeds take to germinate?
Watermelon seeds usually sprout in 5–10 days when the soil is kept moist and warm.

How deep should I plant watermelon seeds?
Plant watermelon seeds about 1/2″–1″ deep and cover them with soil.

When should I start watermelon seeds indoors?
Start watermelon seeds indoors 3–4 weeks before your last frost date.

Can I direct sow watermelon seeds?
Yes. Sow seeds directly in the ground after your last frost, once the soil temperature is over 70°F. In cool, moist soil the seeds can rot before they sprout.

How far apart should watermelon plants be?
Space watermelon plants about 3–4 ft apart to give the vines room to spread.

How often should I fertilize watermelon?
Feed watermelon with a liquid fertilizer once every two weeks.

How can I make my watermelons sweeter?
Water regularly through the flower stage, then reduce watering once the fruits are maturing. Less water at the end improves flavor and sugar content.

Can I grow watermelon on a trellis?
Yes, if the fruits are small. Trellising improves air circulation and decreases disease pressure.

Can I grow watermelon in a pot?
Yes. Choose a pot with ample space for the roots to spread, and fill it with fertile, well-draining soil.