cow manure will be on craigslist. it may not be fully composted but you can ask and get manure that is a few months old. if you have money, composted manure can be found at Home Depot. To grow watermelons, dig a planting hole, plant the seedling, spread the manure, then cover the manure and the grass with cardboard (add bricks as needed to prevent cardboard from flying away, or even better, cover cardboard with wood chips for optimal water retention). if you do not have cardboard, several layers of newspapers will do it.

You need something the grass and weeds won't grow through. To me that's not manure and soil. Put down something like black plastic, black weed barrier, or cardboard that will smother the weeds and grass. You'll get a lot more melons if they don't have to compete with the other vegetation.

I grow mine on black weed barrier fabric and get the best melons I've ever grown. Last year 14 brix, ~14% sugar, and 20 to 40 lbs each.

You get way more than enough heat so something black isn't needed. Some heavy cardboard boxes broken down flat and over lapped does a good job as a temporary ground cover.

i lied, my side yard where my watermelon plants will be growing is 20ft x 5'7". will all 10 seedlings fit?

You really don't need more than two plants of large fruited watermelon for that area. You don't want so many that some go without fruit. If they don't fruit they are just weeds. You could go four plants but still might plant all 10 and thin after they get established to the strongest four.

If they aren't dark green and growing rapidly apply more nitrogen. It depends on your soil but water and nitrogen are my keys for great fruit. Too much of either and they aren't as sweet. Not enough and it really hurts the yield. You want vigorous but not rampant growth.

Sounds good! I started with 3 seeds per pot. I used those organic pots you can put directly in the ground. I don't remember what it was called? I had 12 seedlings now I have 10. I was thinking of planting 5 the most. How do I know which seedlings are strongest? They are all very green standing tall. Also if I take out one will it hurt the other seedlings roots?

Sounds like you have about four pots of seedlings. So plant all four pots spread out. Divide the area into four equal parts. Plant one pot in the center of each area.

Then after they start growing well thin to the fastest growing plant in each area.

Thank you fruitnut for the tips! One more question, when should I plant them? They're almost 2 weeks old and now they are kept outside to get use to the weather and to get sunshine.

I'd plant those four that have two plants each right now. The sooner they are planted the better. Mine planted outdoors in place are about that size. You are warmer than here so it's plenty warm enough to be planted.

After about two weeks thin each pot to one plant.

Will the roots grow through the cardboard?

I would at least remove the bottom of the pot when you plant them out. They are supposed to rot away to let the roots out but when you plant them with the pot a lot of times the roots don't make it out past the pot.

Plant your seedlings in the soil. Then before they start running lay down cardboard around them to cover as much of the grass and weeds as possible. The watermelon will be growing in a crack between pieces of cardboard. Put something heavy on the cardboard so it doesn't move or blow away.

You could also cover the soil with black plastic and allow holes for the watermelon.

Do like they said with the manure and compost, I would use cardboard I think the black plastic will get to hot in the summer the carboard acts as mulch as well keeping in moisture. What variety are you growing? Some varieties like sugar baby do not get as long as most others 8 to 12ft., however they are small melons, crimson sweet are a medium size and do really well for me but the vines can grow up to 20 ft. after fruit sets you can prune the vines, but I do not, to me more leaves mean more energy shade and sugars for the fruit, but I do thin the set fruit to two melons per vine, stay consistent with watering to much varation and the melons will crack, with four plants your side yard will soon be overtaken, try to train the vines so you have room to walk without stepping on them. When you decide if you want to thin your seedlings the best way I have found is to pinch off the one you are culling at the base, this will kill the plant without harming the roots of the other plant . I live in North Peoria and have grown some killer melons it is said that the heat here makes for sweeter melons I am not sure if that really has anything to do with it but they have been really good....Have fun!