I see chopped kale without a Hechsher sold in some kosher supermarkets. Is this OK to buy?

Not at all.

Kale is heavily infested and must be checked.

Method of checking:

1. Soak the leaves in a solution of dish-washing liquid and water. Allow to soak for at least five minutes. Agitate the herbs while they are in the solution.

2. Remove the leaves from the solution.

3. Hold the herbs in a downward position, and direct a stream of water at each leaf while spreading out the herbs with the hand, making sure that every spot is reached by the water.