I really enjoy a good artichoke. A few months ago I would regularly get some artichokes, fill a saucepan with water, and cook them for around a half hour on the stove. I would have the heat high enough to cook them but not to bring it to a rapid boil. I would trim the top of the 'choke off and also a good portion of the stem, and they would turn out perfectly delicious; the leaves yielded generous portions of goodness and as the layers got deeper, the leaves were increasingly tender, to the point that one could almost eat the entire leaf. The heart/bottoms were tender and absolutely delicious. Then I put one on the stove a while back and forgot about it; all the water evaporated and the artichoke was burned and the saucepan ruined! I got a new saucepan and some artichokes the other day and went through my usual preparation; but now pulling the leaves off pulls a lot of stringy fibers from the stem and the leaves seem thicker and yield less edible portions. The bottoms are tough and fibrous as well.
So I’m thinking of what changed; new saucepan which seems to conduct heat better, as water boils sooner at the same heat I was using before. Or is it just a different variety of artichoke, one that is tougher and more fibrous in general? Do I need to just cook them longer or are the “good” artichokes out of season now?
My guess would be that it is the artichokes and not the pan. I always test my artichokes to see if they are done. Stick a fork down the center of the stem. It the fork enters easily, it is done. If not, it needs to cook a little longer. Have you tried this already?
Try steaming them. Boiling leaches out all the vitamins, and the flavor.
The ghost of the artichoke you killed is haunting your kitchen and warning the new artichokes about you. 
I better anoint them with holy olive oil, and maybe some salt and pepper then.
In other news, I got four more artichokes last night. One thing I noticed before but forgot to write was that the 'chokes I’ve gotten lately tend to be fatter with leaves that more tightly conform to the globe shape than some 'chokes I’ve had in the past. I sought out some that had the leaves splaying out a bit more this time. I cooked them for about 40 minutes each in boiling water (I’ll try steaming next time) and lo and behold, they were much better…so it does look like it was the artichokes and not the cooking method.
Good call on steaming them; I used a method I read about online for steaming them in the microwave, and they turned out nearly perfect!
Yeah, I only steam mine. We use a Black and Decker steamer, and it works well.
Also, I use Alton Brown’s method of checking for a good artichoke: when holding the artichoke, it should feel heavy for it’s size with the petals tightly packed. Take one of the petals and bend it backwards. It should fold a bit, and then snap in half. If it doesn’t, that means the 'choke has been sitting a while and may be tough. My whole family loves artichokes, but if they’re in the store and they don’t past the AB test, I don’t buy 'em.
I boil mine for 1.5 hours at least (covered, so they steam inside the pot as well). The resulting broth is excellent as well. 40 mins seems to be fairly short in my experience.
I steam for 45 minutes and they always come out well. I do the fork test as well.