What is the Best Soil for Herbs in a Raised Bed?

“What soil is best to use for my herbs in a raised bed? I have lemon balm, mint, basil, and thyme.” Stacey of Brooklyn Park, Minnesota

Answer: Our Black Gold Natural and Organic Raised Bed Potting Mix is specially formulated for raised beds and has all of the characteristics needed for growing herbs, including good drainage, ample organic matter, and a neutral pH. Additionally, I always recommend that gardeners mix a little natural topsoil into their raised beds at a ratio of one part topsoil to two parts bagged mix. The addition of natural mineral soil will increase the longevity of the mix and provide natural microbes and minerals.

The lemon balm and basil will grow beautifully in the organic-rich mix. In the areas where you plant thyme (or lavender and sage, for future reference), I recommend the addition of a fast-draining mineral amendment, such as sand or gran-i-grit. A small bag will help. Mint is a very aggressive herb that will completely take over a raised bed, so I suggest growing it alone in a large pot.

After your herbs have initially been planted, water them every other day to help them become established. After a couple of weeks, you will only need to water if the soil becomes dry in the absence of rain. Add a slow-release fertilizer for vegetables and herbs at the beginning of the season to ensure that they grow their best. (Click here for more information about growing essential culinary herbs.)

When determining how the amount of mix to add to your beds, use this formula:

How to find soil volume for square or rectangular raised beds:

To find the amount of soil you will need, determine the volume of your square or rectangular bed by measuring its length, width, and height. Then use the following formula: V = L x W x H.

V = soil volume
L = bed length
W = bed width
H = bed height

So, if your bed happens to be 6 feet x 4 feet x 1.5 feet, multiply 6 x 4 x 1.5 = 36 cubic feet. Our raised bed soil is sold in 2.2 cf bales. To determine the amount of bagged soil you might need (36 cubic feet/2.2 cf bales= 16). If you plan to add topsoil at a 1:3 ratio, then you will need 2/3 mix (24 cubic feet (10.66 2.2 cubic foot bags of raised bed potting mix)) and 1/3 topsoil (12 cubic feet of topsoil). If you want to buy topsoil by the yard, then you must know yardage. Divide the answer in cubic feet by 27 to get the number of cubic yards you might need (36/27= 1.3 cubic yards).

Happy gardening,

Jessie Keith

Black Gold Horticulturist



Plants are the lens Jessie views the world through because they’re all-sustaining. (“They feed, clothe, house and heal us. They produce the air we breathe and even make us smell pretty.”) She’s a garden writer and photographer with degrees in both horticulture and plant biology from Purdue and Michigan State Universities. Her degrees were bolstered by internships at Longwood Gardens and the American Horticultural Society. She has since worked for many horticultural institutions and companies and now manages communications for Sun Gro Horticulture, the parent company of Black Gold. Her joy is sharing all things green and lovely with her two daughters.

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