How to Grow Watermelon in the Northwest

Select an early variety of watermelon. These are seeds that are more accustomed to cooler climates, and will germinate and produce fruit earlier in the season than regular varieties.

Fill 4-inch planting pots with potting soil. Insert the watermelon seeds into the soil at a depth of one inch and water until the soil settles. Keep the pots indoors, in a warm, sunny location on a heating pad set at 80 to 85 degrees F. Do this in late April or early May.

Prepare the outdoor garden bed in early June by removing the weeds and covering the site with a 2-inch layer of compost. Turn the compost into the soil at a depth of 8 inches. The garden bed should be in full sun.

Mound the soil in the garden into raised rows that are 4 to 6 inches above the bed. Space rows 7 feet apart. Install a soaker hose along each raised bed for watering.

Cover the rows with black plastic to raise the temperature of the soil. Cut holes in the plastic with a hand spade so you can plant the seedlings. Space the holes 3 feet apart.

Remove the seedlings from their indoor pots and plant them at the same depth in the rows. The plants go in the holes you cut into the plastic. Turn on the soaker hose to water the seedlings from below, so you do not wet the foliage. Keep it on whenever the soil is dry to the touch.

Cover the rows with a plastic cloche, which is a small, portable plastic plant tunnel. The cloche will raise the temperature of the soil. Remove the cloche when temperatures are at least 70 degrees daily.

Reduce your watering by half when the fruit begins to set. Put the watermelons on over-turned coffee cans to keep them off the moist soil common in that climate.