Answer: Growing grapes, either for table use or for making wine, is a rewarding use of landscape space. There's lots to know about grape growing, though, including pruning and training, and there isn't enough space in this forum for me to explain it all to you. However, I found a great reference with diagrams for pruning and suggestions for feeding your grape vines through the Iowa State University. If you disregard the references to the best grapevines to grow (it's a local preference), you'll find lots of other information. Here's the URL: http://www.extension.iastate.edu/Publications/PM1707.pdf
As for watering your grapevines, daily watering is excessive, even in the heat. Try a deep soaking once or twice a week. Here's how you can get to know your soil: Water as usual, wait 3-4 days and then dig down near the plant to check the soil moisture 3-4 inches beneath the surface. If it's still moist, you don't have to water for another few days; if it's dry, it's time to water.
Best wishes with your merlot grapes!
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