This soup is a good source of potassium, vitamins A and C, iron, folate, magnesium, and selenium.

In a large soup pot over high heat, combine the potatoes, asparagus, onions, celery and water. Bring to a boil. Reduce heat. Cover and simmer until the vegetables are tender, about 15 minutes. Stir in the butter.

In a small bowl, whisk together the flour and milk. Pour the mixture slowly into the soup pot, stirring all the time. Increase the heat to medium-high. Keep stirring until the soup thickens, about 5 minutes. Remove from heat. Season with lemon zest and cracked black pepper. Serve in warmed bowls.

• 2 cups peeled and diced potatoes
• 1/2 pound fresh asparagus, cut into 1/4-inch pieces
• 1/2 cup chopped onion
• 2 stalks celery, chopped
• 4 cups water
• 2 tablespoons butter
• 1/2 cup whole-wheat flour
• 1 1/2 cups fat-free milk
• Lemon zest, to taste
• Cracked black pepper, to taste