Home Joys: Growing Sweet Potatoes Here is takes about four months - but since your climate is so different then mine, I won't even be able to guess! I never knew the leaves were edible. we have found that it is best to keep the plants trimmed back. We usually plant the sweet potatoes at the side of the garden and mow off anything that grows into the yard. That way the strength of the plant goes into growing sweet potatoes and not just vines!