Fill a large pot about 1/2 full with water. Place the ham shanks into the water, and as many of the greens as you can fit. Bring to a gentle boil.
As soon as the greens begin wilting, start transferring the greens to the slow cooker. Alternate layers of greens with the ham shanks and jalapeno until the slow cooker is full. Stir in the baking soda, olive oil, pepper and garlic powder. Cover, and bring to a boil on High. Reduce heat to Low, and cook for 8 to 10 hours.