Tannic black tea substitutes

I've had to lay off caffeine and I'm pining for strong tannic black tea. It is actually the dark, bitter tannins I miss. Currently, I'm drinking a roasted dandelion root tea but it lacks body. I believe oak leaves have tannins so when I find some is it okay to just rinse them off and steep and drink?  I would appreciate learning about substitutes.
Thanks!
denise

I like siberian tea (Bergenia crassifolia). You can collect the died off leaves (even in winter). They have a nice aroma and pleasant tannin. I read the fresh leaves are more adstringent tannic, but never tried those.

Philipp,
I will look into this and see if it grows here.
Thanks!
denise

Raspberry leaf is a substitute for black tea.

As to your question about oak leaves  ... try collecting a few young leaves and steep them to see how they taste.

To improve the 'body' of tea, you could try including a dried clove when brewing it. I use 4 cloves per gallon of ice tea. The taste is rather subtle.We really like it.