My Japanese sweet potato (which I planted 2 years ago) keeps popping up new green leaves, despite my harvesting many sweet potatoes this late spring.  I wanted to keep my bulb onions, beets, and beans growing in that bed, so I'd been yanking the sweet potato greens out.  But I thought, "How wasteful!" so, after making sure that they are truly safe and edible, I cooked some and they were delicious!  Now I'm a fan of the greens - they have more vitamins and nutrients than many other green vegetables, have a delightful slightly sweet taste, have beneficial anti-oxidants, and are quick and easy to cook.  I will plant those in the LA Green Grounds teaching garden soon and they will grow for a long time, giving us healthy greens to harvest.  Yes, like many dark green edible plants, they have oxalic acid, but they have much less than regular spinach!

Here's a link, so you can read yourself, a scientific study:

https://www.uaex.edu/publications/PDF/FSA-6135.pdf 

Keep eating fresh vegetables!  There are so many easy-to-grow greens that are quick to cook, tasty, and you don't have to wait months for the harvest, such as with peppers, tomatoes, eggplants, etc.