"You Northerners just don’t know beans,” my Southern friend Stella declared. “They’re always undercooked.”

We’d just finished topping and tailing a pile of garden beans, and the pot of water was boiling hard. We tossed them in and, within a couple of minutes, their green and yellow colors had turned vibrant, then deepened. We drained them after six minutes and refreshed them under cold water, then patted them dry with clean towels.

These green and wax beans are the immature edible bean pods, so it’s important to cook both pod and bean through while being careful not to overcook them. This opens the flavor of the inner bean, resulting in a richer, far less grassy taste.

Those pretty yellow or wax beans are nearly identical to green beans in all aspects except the lush buttery color and a slightly nuttier flavor. They are interchangeable in any green been recipe, as are the purple beans. But purple beans turn green when cooked and are a little tougher than their green and yellow cousins, so give them 30 additional seconds of cooking time in the pot.

My grandmother called these beans “string beans” for the fibrous thread that ran the length of their seams. But these days, growers plant the “stringless” varieties for less fuss in prepping. The tough ends just need to be snipped. Loaded with nutrients, especially Vitamin A and C, green, wax and purple beans are low in calories, too.

Once cooked, all of these varieties will keep several days in the refrigerator — ready for last-minute salads, or to serve with dips, or to add to a quick sauté. But do not dress them until you’re ready to serve because the acid in the vinegar turns the green beans a khaki gray-green.

Cooked beans freeze beautifully. Prepare more than you can use for any one recipe, then freeze and package the rest for a soup or stew on a cold winter’s day.

A pound of beans equals about 3 to 4 cups of cut green beans and will serve about four people.

Beth Dooley is a Minneapolis writer and cooking instructor.