Since ground temps always lag behind air temps, the bed, surrounded by air on five sides instead of one, should warm up faster than the earth. Is that what you meant?

Also, please consider adding a large portion of minerals (soil) to that three feet of compost. it should work out better that way unless you have something special in mind.

Agree with grubby completely, especially about adding mineral based soil (real 'dirt') to your mix. A) because all plants need it and it offers a much broader range of plant nutrients than does just compost, and B) because that 3' of compost will only be about 1.5-2' of compost come spring planting time.

thanks for the idea of adding dirt. I have some left over from another project.

With a planting bed with a soilless mix (compost and other organic material) you may have more problems then those with potted plants do. That planting bed needs some mineral soil in it, about 92 percent mineral soil to about 8 percent organic matter. What everyone considers the best garden soil, loam, is about 92 to 95 percent mineral and 5 to 8 percent organic matter.

kimmq is kimmsr

In his other post he mentioned the compost was his own and about 5 years old, so some mineralization has occurred but more soil would still be advised.

Other Post.

tj

Edit: Ooops. I guess he mention the compost was 5 years old here already.

Compost5 doers not mineralize.

kimmq is kimmsr

Perhaps not the best term for it but I think the point is that after 5 years, compost isn't going to further shrink very fast at all. But I too agree these beds need some soil mixed in.

Since 'mineralization' as it applies to soil science is the decomposition or oxidation of the chemical compounds in organic matter to plant accessible forms, compost does indeed mineralize. But that is not what is meant here when referring to a 'mineral based soil' - a mineral based soil is naturally occurring soil that has resulted from eons of erosion and weathering of rocks - the minerals - combined with organic matter to form 'dirt'/soil. Any garden soil that has not been imported or purchased in a bag is a mineral based soil.