What causes daily morning cough?

Chronic bronchitis? If you are a smoker and have productive am cough for six weeks, you fit the diagnosis of chronic bronchitis. Post nasal drainage from assuming the upright position may also be a cause.
Many possibilities. Chronic morning cough can be caused by many things including bronchospasm from any etiology, gerd, post-nasal drip or even a combination of factors. If the patient is a smoker, malignancy needs to be ruled out as well. See your doctor for evaluation so it can be treated. If you are smoking, you need to quit to avoid further airway inflammation and reduce the risk of sequelae.