Most likely Cleistocactus strausii, although at this age they can be tough to tell from C. tupizensis, C. hyalacanthus, & C. tarijensis.

Thanks so much. From what I can see on the web, now that it's been narrowed down, it appears to be Strausii. However, I noted the other names so when it matures, if it looks different from a Silver Torch, I'll have some other possible names to look at.

Laura,

Generally with South American cactus, you'll have at least two names, with some running luckily to five or six.

The flowers will clinch the ID - C. strausii flowers are quite distinct from the others. C strausii flowers are straight and very hairy on the exterior, and the petals do not flare open on the ends like the others; flowers are also more of a burgundy red too. It might be a few years though before it blooms.

Thanks again for all the info!