Slow Cooker Zucchini Soup

Ingredients (13)

• + 1 ½ pounds sweet Italian sausage add to pantry
• + 2 cups 1/2-inch pieces celery add to pantry
• ✓ 2 pounds zucchini, cut into 1/2-inch slices
• + 2 (28 ounce) cans diced tomatoes add to pantry
• + 2 green bell peppers, cut into 1/2-inch slices add to pantry
• + 1 cup chopped onion add to pantry
• + 2 teaspoons salt add to pantry
• + 1 teaspoon white sugar add to pantry
• + 1 teaspoon dried oregano add to pantry
• + 1 teaspoon Italian seasoning add to pantry
• + 1 teaspoon dried basil add to pantry
• + ¼ teaspoon garlic powder add to pantry
• + 6 tablespoons grated Parmesan cheese, or to taste add to pantry