I eat a lot of kale - both cooked and raw. I am lucky to be able to get it year 'round at farmers markets. The size varies by season. Right now (February) the stems are generally pretty short (5-7") from stem-end to tip of the leaf, but during the warmer months, very often twice that - or more. Every week I cook up a bunch (or two) to store in the fridge for daily use or use it in a few dishes or a salad. Many recipes advise you to de-stem by cutting out the stem from the entire leaf. If I am going to use only four leaves of kale this is fine, but if I am de-stemming two large bunches, I start to feel a little stab-y.
Sometimes I just cut off the woody part of the stems from the bottom of the leaf and don't bother with de-stemming. If the leaves are tender, it's just not necessary. I have tasted the stems and as long as it's not woody or stringy, they are generally tender enough, especially if cooked.
The easiest and fastest way I've found to de-stem kale is to use your fingers to tear a tiny bit of the leaf at the lowest end on both sides of the stem and then, holding the end of the stem in one hand, strip the leaf off with the other, towards the tip end. Think about how you strip rosemary leaves from a stalk. Same deal-io.
It is very easy...
...and very fast...
...and two batches are de-stemmed in no time flat and ready for washing.
I just don't understand why recipes so often recommend that you cook kale in vast quantities of water for 5 or even 10 minutes (gasp!) before sauté-ing or adding to other dishes. Curly kale might be a little unruly (it can be very curly) but you might as well chuck a fist-full of cash into the street, if nutrients (not to mention taste) were dollars, when you boil it. If you must reduce the volume, or need to get the water our of the kale for use in a recipe (as you would by squeezing spinach) either saute or steam it first. If you know how to do this with spinach, you're good to go with kale.
Wash your kale in a really big bowl by filling it up with water. The bowl needs to be big enough so that there is room for any dirt or grit to sink to the bottom - or do it in batches Add the kale leaves (chopped however you plan to use them is easier than full leaves) and swish it around. A lot. Swish it around a few more times and then don't touch it for a few minutes. After it has rested, pick up handfuls of kale being careful not to disturb the water, and place in a clean bowl shaking a little - but not all - of the water off the leaves in the process.
Heat up a large pan or dutch oven with about a tablespoon of oil - medium high - until the oil is shimmery and there's no more than a tiny wisp of smoke. Throw a couple of handfuls of kale in the pan and toss it around with a pair of tongs. Push that batch aside and add a couple more handfuls and toss. Repeat until you've added all of the kale, and it is reduced in volume. Taste it periodically and you shouldn't cook it until it's too limp. I like mine to be brightly colored and tender - not limp and discolored.