The Q&A Archives: Amendments for Alkaline Soil

Question: I am planning a new flower bed, and would like the bed to include hollyhocks and asiatic lilies, and possibly grape hyacinths and narcissus. I live in Missouri and our soil is hard clay (alkaline too, I think). What would you recommend I use for soil amendments?

Answer: Clay soils can be improved with the addition of lots of organic matter. Spread a layer of 3-4 inches of compost and work it into the soil to a depth of 18 inches. Other sources of organic matter would be grass clippings, straw, manure, pine needles, etc. (Don't use wood ashes, which are highly alkaline.) If you want to plant this year, compost would be best, because it's already decomposed and its nutrients would be more available to your plants. Pine needles are acidic and they can on a temporary and localized basis, slightly reduce soil alkalinity. Gypsum or soil sulfur are two other amendments that can reduce alkalinity problems. (Follow package instructions for application rates.) At least once a year, and preferably twice, add several inches of compost to your flower bed. It will help improve drainage in your clay soil and provide nutrients to your plants. You might check with your County Cooperative Extension office for specific info on soil in your county, or the possibility of getting a soil test. They are at: 1507 S. Noland Rd., Independence, 64055, 816-252-5051. Best of luck with your flower bed!

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