Slow Cooker Zucchini Soup

1 1/2 pounds sweet Italian sausage

2 cups 1/2-inch pieces celery

2 pounds zucchini, cut into 1/2-inch slices

2 (28 ounce) cans diced tomatoes

2 green bell peppers, cut into 1/2-inch slices

1 cup chopped onion

2 teaspoons salt

1 teaspoon white sugar

1 teaspoon dried oregano

1 teaspoon Italian seasoning

1 teaspoon dried basil

1/4 teaspoon garlic powder

6 tablespoons grated Parmesan cheese, or to taste

What You Need