Each year I plant morning glories and end up with nice blue flowers but the leaves end up yellow and die. WHY?

There is either not enough nutrients in the soil, or they are not placed in proper light, or they are getting too much or not enough water.

Each year I plant morning glories and end up with nice blue flowers but the leaves end up yellow and die. WHY?
Too much sun light. The leaves are being burned by so much direct sunlight. Morning glories need light but not all day, direct sunlight. Hope that was helpful!
Reply:or a fungus