Mix split peas, water, sherry, sweet potato, onion, garlic and salt in 3 1/2- to 4-quart slow cooker.
Cover and cook on low heat setting 10 to 11 hours or until peas and vegetables are tender.
Stir in spinach, half-and-half and dill weed. Cover and cook on low heat setting about 30 minutes or until spinach is wilted. Season with pepper.