raised bed questions

[cgillett5]

I have recently constructed the exterior of a raised bed for my outdoor cacti. I am in zone 4. I have spent the winter and spring researching which plants are native to my zone. Now my question is what sort of drainage do I need and what about soil?

I plan on having mostly Opuntia in it. There are two other varieties that I have found that are suppose to be cold hardy enough, but I am at work right now, so I don't have their names.

My bed is about a foot above ground level and a foot below. I have removed all the dirt that was in there. My soil is very nice for what most people would call "normal" plants. It's black and rich. From what I have seen as I dug it all out, there isn't any clay in it. I know I will need to replace this soil with something more suitable for cacti. I need advice on drainage and soil mixture.

Thank you in advance for any and all advice. I want to make sure all my plants grow.

[Harriet]

If you post where in zone 4 you are, you may get some area-appropriate responses.

[cgillett5]

Sorry, west central WI. The area I live in is good farm land. Not so good for growing plants that need good drainage. Most of the plants I found have shallow but wide root bases. I planned on approximately 18 inches of soil and 6 inches of drainage. I'm not really sure what would work the best for either.