"Evergreen" is a bunching onion, which is a different species (Allium fistulosum) from common bulbing onions. They are used for scallions exclusively, as they do not form bulbs. "Evergreen" is also perennial, and fairly winter-hardy. Each year the plants will divide from the base to form clusters, much like walking onions. When the cluster grows large it seems to increase the chance of winter kill, so dividing & replanting is recommended. I do this in the Spring, so I can fill in any holes left by plants which did not survive. In Zone 6b, you may have fewer problems.

Several years ago, I did a trial of 9 bunching onions. They were planted indoors mid-April, and transplanted the first week of June. If you are able to plant earlier, adjust your dates accordingly. I planted 3 seeds per cell, and transplanted whatever germinated together, without separating them.

All of the bunching onions reached harvest size the first year. "Evergreen" tends to form one large stalk the first year (up to 3/4" wide) then divide the second year... so plant some for harvest & some to winter over. They flower the second year; but unless you are saving seed, I recommend cutting off the flower stalks as soon as they appear. You may have to be persistent, because the plants will continue to generate new flower stalks. Pruning off the stalks directs more energy into the base, for better multiplication.

do they die back in winter,also do you dig them out to divide them.idk if this is a dum question but why let it winter over, to produce more?
thanks