Direct planting (planting seeds directly into garden bed)
Follow the above instructions for preparing your soil and forming hills. Once your hills are formed and amended with well-aged manure or compost, plant the seeds ½" - 1" deep, sowing six seeds per hill.
When your watermelon plants have reached 2" tall, thin seedlings to 2-3 plants per hill by leaving the healthiest and most vigorous seedlings and cutting the remaining plants off at soil level.
If planting in rows, plant 2 to 3 seeds together ( a couple inches apart from each other) every 18 to 24 inches within the row. Once the seedlings are 2" tall, thin to the best plant per group by cutting the remaining plants off at soil level.
Don't pull weeds up by hand. Hand-pulling could disturb the root systems of the other plants and pull them out of the soil.
Mulching
Applying 2-3" of mulch around the plant will conserve soil moisture and reduce weed growth. Organic mulches like woodchips or straw can also be used when growing watermelons, but do not apply organic mulches until soils are warmer than 75ºF. Applying organic mulches too early keeps the soil cool, resulting in slow growth and shallow rooting.
Weeding
The roots of melons grow close to the surface of the soil, so it's important not to cultivate too deeply or too close to the plants. Cultivate just deeply enough to cut the weeds off below the surface of the soil. Continue cultivating until the vines begin to spread between the rows. Then pull large weeds by hand.
Watering
Regular deep watering is especially crucial during the first 3 to 4 weeks that growing watermelon vines are growing in your garden. Drip irrigation or soaker hoses are the best way to give watermelons a steady supply of moisture. Water deeply and infrequently (1-2 times per week); provide a total of 1-2 inches of water per week.
Cut back on the water once the plants have started to set fruit; over-watering will dilute the melon's sugars, causing it to be less flavorful and lose sweetness. Too much water could also stress the plant and cause less fruit to develop. There is very little benefit in a light watering that only wets the soil's surface. Deep, infrequent, but consistent watering is extremely important especially in the last 2 weeks of growth. Excessive watering at this stage can cause the fruit to split.
Companion Planting and Rotation Considerations
Watermelon doesn't allow much room for companions, and does best when it can sprawl out freely without competing for nutrients with other plants.
You can try planting Marigolds or Nasturtiums in the area which deter beetles, or Oregano which provides general pest protection but it is likely the vines will smother them if planted too close. They need to be in their own pot or raised bed, out of the reach of the encroaching vines.
Because watermelons are in a different class than muskmelons (cantaloupe) and both require the same care, they're good companions. Watermelons and muskmelons share the same nutrient requirements and have the same watering needs; and because they are in a different class, their seeds won't cross-pollinate.
