After washing and chopping it up in big pieces, I don't spend time blanching it.

Unless the stalks are really hard to cook. I don't think this veggie is that difficult to cook, if it is what I think it is.

Actually come to think of it, I very rarely do any blanching of veggies before cooking process. I have the danger of overcooking something, so I don't blanch.

I would tend to sautee or stir-fry such veggies with others for around 15 min. Should be a bright green and soft enough to sink your teeth in, but not mush, dull-yellow green when properly cooked.