Raised bed soil composition

Asked May 1, 2020, 9:20 PM EDT

I am gardening in a suburban plot in Howard County, with very heavy clay soil (see attached picture). To start a garden, I have built large raised beds, 4 feet wide, by 12 feet long, by 2 feet tall. The beds are filled with a type of hugelkultur fill; first a layer of cardboard, then wood, then straw, then leaf, then 6" of compost, and then topped off with 2" of raised bed garden soil. I have planted a green manure (white clover, vetch, and flax). One bed is not growing as well as I had hoped. Do I have too much compost? I have about 4-6" additional room in the beds before I hit the top, so I can add more soil or whatever is appropriate. Thank you!

Howard County Maryland

1 Response

Hi- that's an interesting set-up. We'd like to hear about your garden later this summer.

Slow growth of your cover crops could have been caused by many different factors- planting depth, beetles eating seeds, cold soil and air temps, excessive moisture, etc. We don't think that you have too much compost in the bed. Adding additional topsoil and mixing it with the compost will increase the rooting depth of your crops. It's not essential but will ultimately make the garden more productive.

You may want to terminate your cover crops now so they can decompose for 2 weeks or so prior to planting your food crops.

If you make any additional beds, we suggest you mix the compost and garden soil at the top of the bed, rather than layering these materials.