Answer: If you add sand to clay you will have a hard brick like soil when it dries out. Rather than using sand, it would be better to add generous amounts of organic matter such as compost, and/or chopped autumn leaves, rotted down mulch, milled spagnum peat moss or whatever you can find locally at reasonable cost. This will loosen the soil and help the soil hold air better and encourage healthy roots. Once you have added up to six inches of organic matter and dug it into the top ten inches of soil or so, then you can plant. A variety of perennials should do well for you including hostas, ferns, dicentra, astilbe, pulmonaria, tricyrtis, and so on. After planting, be sure to maintain a three inch layer of organic mulch year round. This will break down slowly over time and continue adding organic matter to the soil on an ongoing basis. In a few instances it may also be helpful to add a small amount of sand to clay soil; if this is the case you would use the coarse builders' sand rather than the finer grained play sand. You could also use a fine grit (such as is sold for chickens). Your local Cornell cooperative extension should be able to advise you as to what is best to use for your particular type of soil. If they suggest adding sand or grit as well as organic matter then they should be aware of local sources for it. Good luck with your garden!
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