We have always been reluctant to sell a triploid watermelon because the seed is so expensive. You are probably going to want to start Ruby indoors with a soiless mix kept at 85 degrees until germ. Also you'll need a pollinator - another neighboring watermelon flowering at the same time. But the result is pretty spectacular. Oval fruit can weigh as much as 15 lbs with delightfully crisp, sweet, red flesh, and of course, no seeds to spit. 5 seeds
Indoors- Individual biodegradable peat/ cowpots 1/2” deep, 3-4 weeks before last frost with soil temperature 70 degrees. Transplant 36” apart after last frost without disturbing the roots.
Outdoors- 1/2” deep after last frost in warm soil at least 70 degrees.
Harvest- Look for the following signs as it does take some practice on telling when they are ready to harvest. The closet tendril to the stem dries, there is a crack in the stem that attaches to the watermelon to the vine, where the watermelon touches the ground it should be a butter yellow color, give it a knock with your hands it should sound hollow, the skin is dull, and slipping of the stem from the melon with slight finger pressure.
Tips- Plant in fertile soil amended with compost or well rotted manure and keep well watered. They benefit from growing on black plastic and by using row covers for weed, insect control, and more rapid growth.