Perhaps you forgot to say what the plants are. Depending on whether these are root cuttings, stem cuttings or simply something else entirely, the answer might be different. Otherwise we can only guess what you mean.

we like to give as much information to answer questions as posable, we can not do this unless you tell us every thing you know about the subject you need information on, and if you dont know then a photo will help us a grate deal.

Sorry, Tropaeolum Speciosum

thanks for teling us the name this of corse is a tuber,I would plant it horizontaly, by the way it is also known as nose-twister or nose tweaker, and white butterfly's love laying their eggs on them.

Many thanks for your information.

if they are 3" bare rooted cuttings then you will see the roots. so the non rooty bits will be the stem. roots down shoots up.