For the last couple of years, I've grown Swiss Chard in my garden. It's easy, prolific, and it doesn't bolt as soon as the days start getting warm enough to enjoy like spinach and lettuce tend to. The taste is tender and delicious, with a mild beet-green flavor. If given enough space to grow, it gets gigantic-- dinosaur food.
I use the leaves in salads as well as adding them into soups and sauces and well, just about everything. We're aren't really "pile of steamed greens" type of people, but they're delicious that way, too, especially with a cream sauce.
This year, I tried a new variety, "Bright Lights". There is ever color under the sun in this mix! It's just gorgeous! I went out a picked a bunch of it to freeze for winter time. I just can't get over the riot of color on my countertop!
I can't help but share some pictures, even though they don't do the color justice. It sort of makes me wish for a good camera to properly capture the colors. (Actually, I really should get out my paints...) Here I've done my best with my point-n-shoot and Gimp: