Hi Sandra, thanks for using Ask Extension.

Black Walnut toxicity has long history and may not be as bad as it is made out to be.  Although some vegetable garden plants do not seem to grow well, many others do not have a problem. However, with a black walnut so close to your underperforming garden, Juglone toxicity is contributing to your garden's troubles.  

Raised beds can definitely reduce juglone exposure if isolated from the native soil.  It is suggested that a depth of 18 to 24 inches for the beds. A root barrier on the bottom (e.g. heavy landscape fabric or quarter inch hardware cloth) to prevent new roots from infiltrating the raised bed is suggested.  The bed should be filled with clean uncontaminated soil with some compost.  Don't overdo the compost.

Black Walnut roots extend 50–80 feet, so at 8 feet distance, your garden is within the high-risk zone. Moving the garden further away could help considerably.  If the black walnut tree is fairly small and is a volunteer, consider asking the neighbor to remove it.  Be sure to keep area free of debris shed from the tree (branches, leaves, husks, walnuts, etc.).

Consider your planting choices, avoid juglones sensitive plants such as tomatoes, peppers, potatoes, eggplant, certain beans, and squash. Keep records of what works and what doesn't.  Plant juglone tolerant plants such as corn, onions, asparagus, beets, melons, brassicas (kale, broccoli, cabbage), and potatoes in raised beds with adequate separation. Consider planting sensitive crops in containers like 5-gallon containers modified for growing (drainage)

Consider other issues that may be influencing the garden.  Get a soil test (Home | MSU Soil Test) to determine nutrient levels and soil pH.  Review drainage, irrigation, sunlight, et al. 

Check out the following links:

Growing vegetable gardens near black walnut trees - Gardening in Michigan

Allelopathy in the Home Garden

Creating Raised Bed Planters | Yard and Garden

Too much of a good thing? Urban gardeners may overdo compost | OSU Extension Service

I hope this helps.

Thank you very much for your helpful response.  I should have also mentioned that the soil test I got from MSU in April, 2025, showed Magnesium off the charts at 275 ppm,  Phosphorus in the Optimum range 55 ppm, and Potassium at 86 ppm.  In addition to the fertilizer recommendation, it stated the organic matter in my soil is 2.9%.  Due to family issues, I was barely able to plant my garden this year, so only guessed at fertilizer around individual planting, and have not added organic matter YET.  If any of this information gives you further thoughts, please advise.  And again, thank you so much for this wonderful service!

Hi again,

Your soil test recommendations for fertilizer and organic matter should be adequate. The high magnesium could be a concern as to how it interacts with calcium and potassium but unless you are seeing specific deficiencies no action is probably necessary.  The pH is a little high but tolerable. This last summer with heat and in some places lack of rain played havoc on many gardens. Please let us know if you have additional issues.  

I hope your garden flourishes!