In a small bowl whisk 4 tablespoons poppy seed dressing and 2 tablespoons white balsamic vinegar.
In a large bowl, lightly toss the 6 cups packed arugula with half the salad dressing mixture.
Top the arugula with 3 cups cubed watermelon, 6 ounces cubed feta cheese, 1/4 cup pickled onions and 1 ounce julienned mint leaves.
Gently toss again and drizzle the remaining dressing on top.
Serve immediately as the arugula will begin to wilt if it sits on the salad too long.
Three Secrets to Choosing a Ripe Watermelon
Look for a yellow “field spot.” A yellow spot from where it rested on the ground is probably the best indication that the watermelon is ripe. It demonstrates that the melon was sitting in the field longer while ripening on the vine. If the spot is white, it has not fully matured yet.
Whether it’s large or small, it should feel heavy for its size. This usually means it’s full of water and will be juicier when you slice it open.
Give it a thump with your knuckles. A ripe watermelon should have a deep, hollow sound when thumped. If it is under or over-ripened the sound will be dull.