Um, the powder is usually made from the seeds, not the leaves. There is a huge difference in flavour. I love the seeds, but hate the leaves. The smell is also very different.
That being said, I do buy the leaves once in a while. They can be a needed ingredient in some dishes. I don't actually hate the leaves if they have been thoroughly cooked, still not a herb I would miss if I couldn't get it.
I usually wrap a bundle of stalks with leaves in waxed paper, label it and put it in a plastic bag in the freezer. I do that with parsley and dill too. I lay the stalks on a piece of waxed paper and roll it up tight, folding in the ends before I finish rolling. Then I put a rubber band around it, before it goes in the plastic bag. When I need some, I expose the leafy end of the herb and I just cut off what I need by cutting thin "slices", until I have as much as I need. I usually don't have to do any more chopping. The rest promptly goes back in the freezer.