I’ve been experimenting with straw bale beds since last fall. I used them in a couple of difficult spots where the soil is very poor and I didn’t have the time or the materials to make the soil suitable for garden use. I now have some opinions about this method of gardening.
To slugs, straw bale beds are like slug motels, and the crop is like the restaurant out front. We have slugs in other parts of the garden, but the straw bale beds are infested with them to a much greater degree than other parts of the garden. I have put diatomaceous earth down on the beds around the plants, and that seems to have slowed them down, but because of their very porous nature, the straw bale beds require a lot of diatomaceous earth to be spread on them. I don’t know how long it will continue to protect the plants. We’ve had a lot of rain, so I’m not hopeful that it will be very long. I’m going to experiment with using unused coffee grounds to see if that will do the job as well. I don’t like using diatomaceous earth, for one thing, because it also kills beneficial creatures like pill bugs, and also, because you don’t want to get it on your skin or breathe it, and I don’t like working with things that are so dangerous that you don’t want to get them on your skin or breathe them. I’ll provide updates when I have an idea whether or not the coffee grounds work.
So my opinion is that unless the only area people have available to put a garden is one with very poor soil, and they don’t have the time or money to work with the soil to make it suitable for a garden, or they need an instant garden that requires almost no effort to prepare, straw bale beds are not a particularly good choice. I will probably not ever use this method again.
Update 8/27/13: The coffee grounds worked for a little while and then stopped working. I think it would be very expensive to try to solve the slug problem with coffee grounds. If I were to try straw bale beds now for the first time, I would probably experiment with Surround crop protectant, which is made from kaolin clay, and neem oil sprayed on the crops themselves as a way of repelling insect pests and slugs.