Q: I’m planting a bed of white tulips, emulating Vita Sackville-West’s idea of a white garden for moonlight viewing. I have a quantity of seashells that I want to use over my bed. Would that be too much calcium in the soil?

A: Seashells are made of calcium carbonate, the same stuff as garden lime. If you’ve ever used powdered garden lime, you know how dusty it can be. Limestone must be ground very finely in order to have it dissolve into your soil. Although seashells are composed of calcium carbonate, they are so large that they do not dissolve very fast. I doubt very much that using them on top of the soil will change its calcium content or pH.