This is Tuscan kale (aka black kale, cavolo nero, dinosaur kale, lacinato kale). According to everything I've read, it's become very popular over the past several years, especially with Italian chefs who often pair it with beans or pork. For starters, it's a beautiful plant. The leaves are a rich, blue-green and have a gorgeous texture. Just look at it--could anything look more hearty and healthy?
Speaking of healthy, kale is loaded with vitamins A and C, along with calcium, iron, and cancer-fighting compounds. That's great, but what does it taste like? Unfortunately, most of what I found written about the taste uses comparisons to other vegetables to describe it. Okay, it's "meatier than Swiss chard, sweeter than collards and more mellow than peppery mustard greens" , but that doesn't help me much, having never tasted chard, collards, or mustard greens! I do like the sound of "sweeter" and "more mellow" though!
Next we have red Russian kale, with its jagged, red-tinged leaves. This is supposed to be a particularly tender and sweet variety of kale. I'm not going to spend too much time figuring this out, but the difference between this and the Tuscan kale has to do with the species (napus vs. oleracea). If you really want to know, read this! The bottom line seems to be that this is a less "cabbagey" variety of kale.