Planting

Direct seeding is the most common method of planting. In cooler climates, it may be necessary to start the seedlings in a greenhouse to ensure good germination.

Seed rates per ha are 1–2 kg for direct-seeded and 0.3–0.5 kg for transplanted watermelon.

Plant spacing requirements vary depending on variety selection, growing area, time of planting, and soil type, but should be around 60-90 cm and approximately 2 meters between rows.

A. Direct seeding:

Watermelon seed should not be planted until soil temperatures are warm enough to ensure rapid germination. Plant after the soil is warm and when all danger of frost is past.

Triploid plant population density should be 10 to 20% less than that recommended for production of standard watermelon varieties.

Per hill, 3–4 seeds are sown at a depth of 3–4 cm; 3–4 weeks after sowing, at the 2–4 leaf stage, seedlings are thinned to 1–2 per hill (Thinning is practiced 15 to 25 days after sowing). The plants should be thinned to one plant per hill (two if selection is not good).

Seed will remain viable for at least 8 years when stored dry at temperatures below 18°C.

There is no seed dormancy in cultivated seed- and watermelons, but germination is retarded under high temperature regimes.

Germination can be accelerated by pre-soaking in water for 24 hours after scarifying the seed at one end, especially for cultivars that have a hard seed coat. When planted in warm soil, seedlings will emerge in a week or less.

Use fungicide-treated seed. Watermelons are subject to damping off and decay in cool wet soils.

B. Transplanting:

Transplanting watermelons offers several advantages:

1- Plants can be produced under greenhouse conditions when outdoor conditions are not conducive to plant growth.

2- Seed-use efficiency increases, which is especially important with costly hybrid and triploid seed.

3- Soil crusting and damping off, detrimental to seedling growth, can be eliminated or reduced.

4- Planting depth is uniform.

5- It usually results in earlier harvests.

6- It is the only cost-effective way to grow seedless watermelons.

Watermelons suffer transplant shock if the roots are even minimally disturbed. So seedlings must be grown in containers such as peat pots, Speedling trays, or Jiffy pots to be successfully transplanted.

Sow seeds in small plastic pots or containers using a potting mix that has good water-holding capacity and good drainage such as peat moss, commercial potting soil, or a potting mix prepared from soil, compost, rice hull, and vermiculite or sand.

Sow one to two seeds per container for open-pollinated varieties and one seed per container for hybrids to reduce seed costs. Pinch off or cut seedlings to avoid disturbing the roots. Do not pull seedlings out of the container to thin.

1- Watering:

Uniformly moist media will ensure good germination, but overly wet media will encourage damping off and high seedling mortality.

Established transplants should be watered only when necessary. Excessive watering leads to succulent plants with restricted root growth. Water should be applied only when the surface of the media is dry to the touch.

As plants grow larger, their water needs will increase. They may need water daily when approaching transplant size. The media should be moistened thoroughly until water drips through the container’s drain holes.

Water the seedlings in the morning, to allow the foliage to dry before night. Wet foliage encourages disease.

2- Fertilizing:

Plants are fertilized every three days with a solution containing 50 ppm N from Ca(NO3)2 and KNO3 from cotyledon expansion until the first true leaf is fully expanded, then with a 200 ppm N solution applied every other day until the second true leaf is fully expanded, finally the fertilizer is reduced for several days before transplanting to the field.

3- Hardening-off:

Watermelons need not undergo a long hardening-off period; three to four days are sufficient.

Hardening-off can be initiated by reducing greenhouse temperature and by withholding water or limiting fertilizer. Hardened plants are more able to withstand chilling stress, mild water stress, drying winds or high temperatures. Hardened plants generally produce new roots more rapidly than unhardened plants.

4- Planting:

Plants generally will take three to five weeks to be field ready depending on variety and growing conditions. Plants grown under less than ideal conditions will take longer to produce.

Seedlings are ready for transplanting when they have 2 or fewer true leaves at the time of transplanting. Older plants establish very slowly in the field.
Bare-root plants will not survive so pull seedlings with their root balls intact before transplanting.

Transplant seedlings into the field at spacing similar to those used for the direct seeding method.

Transplants should be watered as soon as possible after transplanting to remove air pockets surrounding the roots and to ensure sufficient soil moisture for good root establishment.

If you grow seedless melons, you must also plant a row of a standard seeded variety for every three rows of the seedless melons. The seedless melon varieties do not have the fertile pollen necessary to pollinate and set the fruit.
Use a starter fertilizer solution when transplanting. Use a water-soluble fertilizer such as 10-34-0. Mix 1 quart of this material in 50 gallons of water.