Well, it depends on what you want to do with them. Mature usually means the same thing as ripe, and they'll be mature when they're red. That said, many peppers are edible while green (like bells), they just don't have as good a flavor.

If you want a milder pepper, go ahead and pick it now. If you're looking for full flavor or to harvest seeds, let them finish turning red.

If you want to encourage more pods, go ahead and pick them now. The plant wants to make mature pods with mature seeds in them, if you let the first ones go all the way the plant will be less inclined to set more right away. If you pick them before they mature, the plant is encouraged to set more pods to try and make up for the fact it lost the first ones.

I suppose by "mature" I just meant edible (done growing, but not yet ripened . . . like a green bell pepper). I just wasn't sure how to tell if they were at the point of being harvestable. I'll probably pick them tomorrow and see how they taste.

You can pick peppers at any stage and they will be edible, the hot ones will be more mild the younger they are.

Those look delicious, and I'd pop them into a stir fry at once !

That is a nice looking pod for sure. Like Josh says, the difference between the two varieties is subtle but he knows. I thought I was growing sweet bananas last year by the name on the package and turned out to be Hot Hungarian Wax. They sure were not "sweet" peppers. Josh is the one who ID'd them for me. Either way, I think the Hot banana and Hot Hungarian are close enough that you wouldn't be able to tell the difference. And I agree that harvesting them while still yellow ensures firm fruit. I let a few get red last year and they were already starting to wrinkle and soften on the vine before completely red.
Bruce

The pods almost look more like Hot Banana to my eye, having seen both varieties growing together.
Regardless, they are edible/ready for harvest as soon as they go grom green to yellow. If you want to
pickle them or can them for sandwich rings/slices, et cetera, I recommend that you harvest the pods
while they are yellow (so that they'll be firm and maintain their integrity when processed).

I thought the two were just different names for the same pepper. Shows what I know! I went back and checked the labels, and sure enough they are Hot Bananas rather than Hungarian Wax. Thanks for the ID!

I picked these peppers, and I think it was a bit premature. The flavor and heat were both less than expected. The same plant has two more large pods right now and I'll wait a bit longer this time.

From what I understand, you can tell the difference between banana and Hungarian Wax by the immature pods. If they begin growing pointing straight up in the air and only hang down after they get full size, then you have a Hungarian Wax. If they point down while maturing, you have a Banana Pepper.

Last year I thought I was growing Hot Banana Peppers but was told otherwise when I posted a picture. Here is a couple photos of my Hot Hungarian Wax Peppers from last season. They clearly how the pods point skyward.

Bruce

Great pics, Bruce!

Chisey, I'm glad to hear that they're Hot Banana ;-)
Give 'em time, they'll taste better.

Josh

Esox, what a beautiful plant! It looks like I may have gotten a mislabeled pepper plant...mine aren't standing up.