Raised vegetable garden - Ask Extension
Last year, we started a raised vegetable garden because it was in a low spot and sometimes water settles there after a storm. We purchased and filled...
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Raised vegetable garden #893726
Asked March 06, 2025, 8:40 AM EST
Last year, we started a raised vegetable garden because it was in a low spot and sometimes water settles there after a storm. We purchased and filled with bagged "top soil" which isn't actually soil but organic matter almost like mulch. We mixed in a liberal amount of leaf gro and mushroom compost. The vegetable garden had a slow start last year but eventually took off and performed well.
I'm wondering how to prepare the soil for this year. The "top soil" has broken down into a real fine, light, almost dusty material though some larger woody pieces remain on top. I plan to amend with more compost on top.
Should I add actual inorganic topsoil that we had dumped onto our property or leave it as is? If I add actual soil, I assume I should mix it in with the material already present.
Thanks!
Baltimore County Maryland
Expert Response
It's frustrating when gardens get off to a slow start but it sounds like you are on the right track now. It's hard to say why that happened- could've been weather or other environmental affect, or even something like the fact that
mushroom compost sometimes has high salts, which could have impeded root growth for a while last year until it leached out.
If you believe the soil is compacted beneath the all-organic matter raised bed, it would be helpful to loosen it with a garden fork- even if that means pushing the raised bed media to the side temporarily. This loosening may not be necessary if water stands for only a short time, and only after extreme rainfall- >2 inches.
As far as topsoil goes, it is not regulated and is really mostly mineral, so your addition of plenty of Leaf-gro and other composted organic material was a good choice.
If the topsoil is high-quality- it should smell earthy, and have a good crumb structure (large aggregates with a lot of pore spaces of different sizes)- then mixing it with the all-organic matter bed media is a good idea. The mineral soil will help hold water and nutrients. The total volume of raised bed media can be 30-50% topsoil.
If you have questions about the topsoil quality you can have it tested and incorporate a smaller volume to start with.
Here is our soil testing information:
https://extension.umd.edu/resource/soil-testing-and-soil-testing-labs/
Christine
mushroom compost sometimes has high salts, which could have impeded root growth for a while last year until it leached out.
If you believe the soil is compacted beneath the all-organic matter raised bed, it would be helpful to loosen it with a garden fork- even if that means pushing the raised bed media to the side temporarily. This loosening may not be necessary if water stands for only a short time, and only after extreme rainfall- >2 inches.
As far as topsoil goes, it is not regulated and is really mostly mineral, so your addition of plenty of Leaf-gro and other composted organic material was a good choice.
If the topsoil is high-quality- it should smell earthy, and have a good crumb structure (large aggregates with a lot of pore spaces of different sizes)- then mixing it with the all-organic matter bed media is a good idea. The mineral soil will help hold water and nutrients. The total volume of raised bed media can be 30-50% topsoil.
If you have questions about the topsoil quality you can have it tested and incorporate a smaller volume to start with.
Here is our soil testing information:
https://extension.umd.edu/resource/soil-testing-and-soil-testing-labs/
Christine
