It is a very unusual method of gardening so you might get more info from a site that focuses on the method rather than one that is traditional gardening oriented. I did find this one long discussion about it from over on the Garden Experiments forum.

And a Google search pulls up several links to info on how-to do it and I linked a set of step-by-step videos below and I hope they are of help.

Just a guess on my part but I would suspect, from what I have read, that your bales are too fresh since partially decomposed bales is what is called for. But it looks like you could still hollow out the core and fill it with potting soil for planting.

Hope this helps.

Dave

Here is a link that might be useful: Straw bale gardening videos

I had never heard of that method of gardening until last spring, when the clerk at the local gas station was telling me about it. She said you had to wait 3 weeks before planting.

I asked through the summer how it was going, and she said the seeds sprouted, but they weren't doing well. By the end of summer, she declared it a total disaster and a waste of effort (not to mention not getting much in the way of crops). She said something hatched and the bales were surrounded by clouds of some kind of small flying insects.

She said she would never do it that way again.

Then I googled 'bale garden failure', and got lots of hits agreeing with her view. Below is one of them.

Sue

Here is a link that might be useful: Baling out of the perfect garden dream

Thank you for the information digdirt and belgianpup.