How do I get this slot ready for planting?

I don't think it's tree roots. But some are still a thumb thick a foot deep in the dirt but it's longer that that. I go a bit deeper but end up cutting it. Those plants have spikes on the top.

Last frost date is end of April. When should I start them?
This are store bought and have been on a drk corner under a kitchen table. I have a few more, do these need to be chited? If so, it's just a day or two before they go on the soil, right?

I've never grown anything, or tryed to. This is all a first to me.