Best soil mixture for raised garden beds

Asked April 14, 2019, 8:36 AM EDT

Hi there - I'm interested in some science to point me in the direction of the best soil mixture for a raised garden bed for vegetables (tomatoes, cucumbers, peppers, beans, leafy greens, carrots), fruits (muskmelon, strawberries) and flowers (marigolds, nasturtium). I've heard 1/3 compost, 1/3 vermiculture, 1/3 peat moss (Mel's mix) and heard that I need topsoil. I picked up some compost (leans more alkaline 7.4-8) and bark mulch from the Dept of Public Works in College Park, MD, but I don't have a truck and don't know where to get topsoil if I really need it. Thanks!

Prince George's County Maryland soil vegetables

1 Response

Hi- we aren't aware of research studies on raised bed soil. We recommend the following approaches:
1. Fill the bed with a mixture of compost and purchased topsoil in a 1:2 or 1:1 ratio. There are vendors who sell topsoil mixed with compost and will deliver. Topsoil sales are not regulated in Maryland. Go to a reputable nursery or topsoil dealer and ask questions about where the soil comes from, what kind of soiling testing is performed, what the pH is and if anything has been added to it. Examine the soil before purchase or delivery. Topsoil should be dark and crumbly with an earthy smell. Do not purchase if the soil is foul smelling, has grayish mottling or a chalky texture.
2. Fill the bed with compost and a soilless growing mix in a 1:1 ratio. Soilless media typically contain ingredients such as peat moss, composted bark, perlite, vermiculite, compost, and coconut coir. They improve drainage and water holding capacity but are costly.
3. If appropriate you can also add to the beds the top 2-3 inches of topsoil surrounding the beds to the beds.