Planting watermelons at the right time is key to a successful harvest. In my experience growing watermelons in warm regions, I’ve learned to wait until the soil temperature reaches at least 70°F (21°C) before planting seeds directly in the garden. This typically happens 2 to 4 weeks after the last spring frost. Watermelon is a heat-loving crop—originally from Africa—and it thrives in a long, warm, dry growing season. For best results, aim for daytime temperatures between 70°F and 85°F (21–29°C) and nighttime temperatures between 60°F and 70°F (16–21°C). Most watermelon varieties need 75 to 90 frost-free days to reach full maturity.
While you can start watermelon seeds indoors, I’ve found that direct seeding tends to produce stronger, deeper-rooted plants. Indoor seedlings grown in pots—especially without bottom heat to keep the soil around 75°F (24°C)—often develop shallow or distorted roots. These transplants usually need more frequent watering once planted out. If you must start seeds indoors due to a short growing season, be sure to use biodegradable pots and warm soil to minimize transplant shock and encourage better root establishment.
I grow watermelons in light, fertile, deep loam, or sandy soil. Make sure your soil is well-drained. Add aged compost or well-rotted manure to the soil and turn the soil to a depth of 8 inches (20cm) or more. Watermelons are heavy feeders. Add bone meal, greensand, or granite dust to the planting hole.

Planting watermelons on mounds or hills is one way to ensure the soil is sufficiently warm for watermelons. The higher the mound the warmer the soil. Vines can also be trained down and around the hill rather than letting them run through the garden. Vines commonly grow 6 to 12 feet (2-4m)long. Some small varieties can be grown in a container or trained to a trellis.
Watermelons are ripe when they make a “punk” sound when struck by knuckles. A “pink” or “pank” sound means the melon is not ripe—according to Mark Twain.
Watermelons are easy to grow from seed. They simply require warm soil, a long warm growing season, plenty of space, and plenty of water.
Watermelons with red flesh are most common, but there are also watermelons with white, yellow, orange, and pink flesh.
Here is our guide to growing watermelons from seed. We also give you a watermelon growing calendar to help you get started.
My Watermelon Growing Quick Tips
- Sow watermelon seeds 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 seeds can be started indoors 6 to 8 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 growing room.
- Watermelons mature 70 to 100 frost-free days after sowing depending on the variety.

Watermelon Planting Details
Here’s a checklist I use when sowing watermelon seeds:
- Sowing depth: ½ -1 ½ inches (12mm) or slightly more
- Space between plants after thinning: 2-6 feet (30-45cm)
- Days to sprout: 4-10
- Days to harvest: 75-90
- Storage period: 1 week refrigerated
- Seeds per 100-row feet: 1 ounce
- Suggested varieties: Black Diamond (90 days), Charleston Gray (85 days), Crimson Sweet (80 days), Sugar Baby (75 days).
Watermelon Seed Starting Basics
From my years in the garden, I’ve found the following helpful:
- Seed-sowing depth: 1inch (3 cm)
- Seed starting tips: Sow 2-3 seeds per individual peat pot or biodegradable pots indoors. Use a sterile seed starting mix or potting soil. Bottom heat is not necessary but it will speed germination. Use low heat if you use a heat mat.
- Pre-sprouting seeds: Lay the seeds on a damp paper towel, roll up the towel, and place it in a plastic bag; seal the bag and keep it in a warm place until seeds germinate; then place seedlings in individual pots.
- Seed-starting soil temperature: 80-90°F (27-32°C)
- Indoor seed starting time: Start indoors as early as 4 weeks before the last frost in spring; not sooner than 3-4 weeks before transplanting outdoors. Thin seedlings to the strongest plant after seedlings have formed their true leaves.
- Light requirements: Full light
- Transplant time: Transplant outdoors two weeks after the last frost. Avoid disturbing the roots when transplanting.
- Direct sowing time: Plant seeds after the danger of frost is past and when temperatures average 70-85°F (21-29°C). Use black plastic sheeting or black plastic mulch to warm the soil early in the season and conserve moisture in hot weather. Protect young plants with floating row covers or cloches.
- Spacing in the garden: Plant in hills, one or two plants per hill, spaced 6-8 feet (2-2.5 m) apart. Amend the garden soil with aged compost or aged manure ahead of planting.
- Seed germination: 3-10 days
- Watermelon flowers: Monoecious (male flowers and female flowers on the same plant); the first female flowers to appear are the ones most likely to set fruit.
- Pollination: Insects, bees
- Cross-pollination: Can cross-pollinate with other varieties. Cage plants or bag blossoms to prevent cross-pollination. Hand-pollinate or introduce insects.
- Isolation distance: 800 feet to 1/2 mile; isolate plants if you plant to save seeds
- Days to maturity: 70-110 days from planting depending on the variety. Be sure to consult the seed packet for days to maturity and mark your garden calendar. For large fruit cull the growing fruit so that only one or two remain on the vine.
- Harvest time: Harvest when the fruit rind that touches the ground turns yellow; harvest when the tendril closest to the fruit turns dry and black. You can also test watermelon ripeness by rapping the melon with your knuckles; if if sounds hollow it’s ready. Use a sharp knife to cut ripe fruit away from the vine. Decrease water a few days before harvest to increase the fruit sugar content.
- Seed saving: Save seeds from fruit with the best flavors, preferred shapes, and colors
- Seed processing: Scoop out seed; rinse away pulp and dry for 1 week. Seeds should be thoroughly dry before storing.
- Seed vitality: 5 years. Store seed in a cool, dry, sealed container.

Watermelon Sowing and Planting Tips
Start watermelon seed indoors 3 to 4 weeks before transplanting seedlings to the garden; set out transplants 2 or more weeks after the last frost in spring. (Seedless watermelons are hybrids; these cultivar plants are most easily grown from cultivar transplants purchased at the garden center.)
- Grow watermelons from seeds or seedlings.
- Seed is viable for 4 to 5 years.
- 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 home 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.
- Watermelon seed germination occurs in 3 to 10 days at 80°F (27°C) or warmer.
- Transplant seedlings to the garden bed 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.
- Watermelons can be grown in containers; use a 10 to 15-gallon container and set a trellis in place to grow the vine up. Small watermelons are easily grown on trellises.
- Water to keep the soil from drying. Mulch around plants to conserve soil moisture. Watermelons have a very high water content; the soil must never go dry.
- Fertilize with fish emulsion or a soluble complete fertilizer at half strength.
- Add aged compost to planting beds in advance of transplanting. Watermelons like sandy, humus-rich soil.
- Watermelons prefer a soil pH range of 7.0 to 8.0. Perform a soil test before planting.
- Grow watermelons in full sun for the best plant growth and 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, and 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
I’ve grown watermelons in three different regions of the country. I use this calendar whereever I am.
- 6-8 weeks before the last frost in spring: start seed indoors for plants that will be transplanted into a plastic tunnel in 4 weeks.
- 4-5 weeks before the last frost in spring: start seed indoors for seedlings to be transplanted into the garden.
- 2-4 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.
Melon Planting Dates
(These dates are for the Northern Hemisphere)
Average date of the last frost | Planting dates |
Jan. 30 | Feb. 15-Apr. 1 |
Feb. 8 | Feb. 15-Apr. 15 |
Feb. 18 | Mar. 1-June 1 |
Feb. 28 | Mar. 10-June 1 |
Mar. 10 | Mar. 20-June 1 |
Mar. 20 | Apr. 1-Jun3 1 |
Mar. 30 | Apr. 10-June 15 |
Apr. 10 | Apr. 20-June 15 |
Apr. 20 | May 1-June 1 |
Apr. 30 | May 10-June 1 |
May 10 | May 20-June 10 |
May 20 | June 1-20 |
May 30 | |
June 10 |

Watermelon Recommended Varieties
- ‘Sugar Baby’ and ‘Sugar Bush’ are small, 8-10 pounds.
- ‘Fiesta’, ‘Regency’, and ‘Sangria’ are 20 to 25 pounds—all are very sweet.
About Watermelons
- Common name: Watermelon
- Botanical name: Citrullus lanatus
- Family: Cucurbitaceae
- Life cycle: Annual
- Fruit type: Berry
Botanical Name: Citrullus lanatus var. lanatus
Melons are a member of the Cucurbitaceae family; other cucurbits are cucumbers, squash, watermelon, and pumpkins.
Watermelons Overview Post:
How to Grow Watermelons from Seed to Harvest: Ultimate Guide for Sweet, Juicy Success
Melons Overview: The Ultimate Guide to Growing Melons: From Planting to Harvest
Related Posts:
Starting Watermelons Right
- When and How to Start Watermelons: A Seed-Starting Guide
- Watermelon Temperature Needs: Warmth, Frost, and Growth Milestones
- Soil Prep and Mulching Tips for Healthy Watermelons
Planting & Space Planning
- How Much Space Do Watermelons Need?
- Growing Watermelons in Containers: Tips for Small Gardens
- Growing Watermelons Vertically: Tips for Small Gardens
- Companion Planting for Watermelons: What Works and What Doesn’t
Watermelon Care Through the Season
- Caring for Watermelon Plants Through the Season
- Watering Watermelons: How Much and How Often
- How to Feed Watermelons: Fertilizer Schedules and Organic Options
- Watermelon Pollination Tips: Helping Watermelons Set Fruit
Dealing with Pests and Diseases
Knowing When to Harvest
Choosing the Right Varieties
- Watermelon Varieties by Size: From Personal Melons to Giants
- Top Watermelon Varieties for Short Growing Seasons
- Best Long Vine Watermelons for Large Gardens
- Best Watermelon Varieties for Small Spaces (Bush & Short Vines)
- How to Grow Seedless Watermelons Successfully
Enjoying the Harvest
- Preserving Watermelons for Fresh Eating and Preservation
- Watermelon Flavor Pairings to Complement Your Harvest Table