They are more determinate that tomatoes, so I wouldn't prune them. When I've grown tomatillos they've produced all at once, and assumed a "candelabra" growth habit similar to mole peppers. I think they are tougher and easier to grow than tomatoes, and in fact I worry about them getting away from me and becoming weedy. Happy salsa verde!

Agree - they (tomatillos) are not usually pruned. Doing so will substantially reduce your production.

Do they have sucker branches that should be pruned? Is there a main stalk to keep clean?

But for future reference, neither are tomato plants - pruned that is. ;) Pruning is OPTIONAL, not mandatory and depends on how you support them and what type they are. So called "sucker" branches do not have to be removed and believe it or not, many gardeners don't remove them, and stems do not have to be "kept clean".

So if you are also growing tomatoes you might want to do some reading about pruning over on the growing tomatoes forum here.

As to BER (blossom end rot) it's possible but it usually isn't a problem because they are a small fruited variety.

Hopefully there are two plants because it takes more than one to pollinate effectively for the best production. If there was more than one in the pot as is often the case it would be best to separate them when planting but it may be too late for that now.

Dave

Here is a link that might be useful: How to Grow Tomatillos

Great! Thanks for the help. It'll be fun to see what they do. I'll leave them alone, which is kind of my preference anyway. Thanks, again.