Answer: Usually, morning glories and sunflowers are started in the ground where they are to grow because they are difficult to transplant. They also grow very fast and would quickly be too tall for the cold frame.
Using a cold frame can be a bit of a trial and error. Usually you want to place it in a location that is sheltered from the wind, and in a spot that faces south to maximize the sunlight. A spot on the ground and up against a building will allow the cold frame to hold heat better at night and protect plants from frost a little better as a result. An elevated deck may be colder than a location on the ground because the air circulates beneath it. On the other hand, you also need to be able to get water to the plants easily and it is nice to have it handy where you will remember to check on it often.
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