Seeded Watermelon Growing Guide

 

Watermelon (Citrullus lanatus)

 

Watermelon is a warm-season crop in the same family as cantaloupe, squash, cucumber, and pumpkin. Watermelon varieties are categorized into three main classes based on seed development: open-pollinated, F1 hybrid, and triploid (seedless). Fruit varies widely in size, shape, rind pattern, and flesh color.

Temperature

 

Watermelon seed germinates at soil temperatures ranging from 68–95°F, but germination below 70°F is slow. At approximately 77°F, seedlings should emerge in about 5 days. Seeds should be planted only after soils have warmed sufficiently for rapid, uniform germination.

Seedless Watermelon: Triploid watermelon seed benefits from especially warm germination conditions. Maintaining temperatures around 90°F with high humidity until emergence can significantly improve germination. Seedlings generally emerge within 4–5 days and are then grown in the greenhouse for approximately three weeks before transplanting.

Planting too early can delay germination, create uneven stands, and increase the possibility of crop loss. Although early plantings can provide earlier harvests, balancing early and later plantings can help provide more consistent production.

Soil

 

Watermelons perform well in most well-drained soils, although sandy loam soils are generally preferred. When possible, select fields that have not been planted with cucurbit crops such as cantaloupe, cucumber, squash, or watermelon for at least five years.

Raised beds are particularly useful for early-season production because they warm quickly and improve drainage in heavier soils. However, raised beds can dry more rapidly, so careful attention to moisture is important, especially during the first two weeks after emergence. Avoid soil compaction, which can severely restrict root development.

Planting

 

Transplanting allows watermelon plants to be started under controlled greenhouse conditions when outdoor conditions are unfavorable. It also improves seed-use efficiency, which is particularly important for expensive hybrid and triploid seed, and can provide more uniform establishment and earlier harvest.

Transplants must be handled carefully because young watermelon seedlings are fragile and susceptible to frost and transplant damage. Transplant production may also increase the risk of certain diseases, including fruit blotch.

Transplanting Guidelines Plant seed approximately 1 inch deep. Seed requirements generally range from 1–2 pounds per acre depending on seed size, germination, and spacing. Set transplants slightly deeper than they grew in the greenhouse to help protect the root and stem interface from wind damage. Water immediately after transplanting to eliminate air pockets and encourage strong root establishment.

Peat Pots: Plant peat pots completely below the soil surface. Any exposed portion can act as a wick, drawing moisture away from the root zone and increasing the possibility of moisture stress.

Spacing

 
In-Row Spacing 24–48 inches between plants.
Between Rows Approximately 72 inches between rows.

Harvest

 

Watermelons are considered optimal for eating when the flesh develops good sweetness, crisp texture, and the characteristic mature color of the variety. Because rind appearance does not always indicate internal quality, soluble solids can be checked with a hand refractometer. High-quality watermelon should generally contain 10% or more soluble solids in the center of the flesh.

Signs of Maturity
  • The tendril nearest the fruit wilts and turns brown.
  • The ground spot changes from white to light yellow.
  • The sound when thumped changes from a metallic ring to a softer, hollow sound.
  • Green bands on striped varieties may begin to break where they intersect at the blossom end.
  • Certain varieties develop noticeable ribbed indentations along the fruit.

Immature melons may develop additional red color after harvest, but their sugar content will not increase. Overmature fruit can develop a mealy texture and poorer internal color, so accurate harvest timing is important.

Watermelons intended for distant markets are generally harvested mature but not fully ripe to help maintain texture during handling and transportation. For best eating quality, watermelons should generally be consumed within 2–3 weeks after harvest.

Harvest Carefully: Cut watermelons from the vine rather than pulling, twisting, or breaking them off. After cutting, turn the melons with their bottoms facing down to help prevent sunscald.

For More Information

 
→  Penn State Extension – Watermelon Production
→  UGA Extension – Watermelon Production
→  University of Kentucky – Watermelon Crop Profile
→  Printable Version

Grow Watermelon

 

Explore our selection of watermelon seed for producing sweet, flavorful fruit for fresh markets, roadside stands, and home gardens.

Shop Watermelon

Watermelon

Looking to get started by growing your own watermelon from seed? Click on the button below to get started.

Shop now
Seeded Watermelon Growing Guide

There are no products listed under this category.