Do you use Epsom Salt on your tomatoes? Do you know why? Are you sure it really works?
Many garden practices are based in folklore and some remedies simply don't work. I highly recommend that any serious gardener learn the science behind garden folk remedies. Some may work as indicated, some may not do anything, and some may actually cause harm. I suggest a very good book on this very subject : The Truth About Garden Remedies by Jeff Gillman. With graduate degrees in entomology and horticulture, Gillman brings scientific rigor to the topic of commercial, homemade and 'traditional' garden remedies.
"Gillman teaches gardeners to think about what they do, know why they're doing it, and observe the results, trusting their knowledge and experience over claims made by companies, 'experts' or garden folklorists." —Publishers Weekly
"The results are fascinating and occasionally disappointing. . . . The Truth About Garden Remedies is a book many of us will want to consult frequently." —The American Gardener
"Whenever I hear someone offer a solution to a garden problem, I immediately check [The Truth About Garden Remedies] to see if it will work." —Horticulture
"While entertainingly relating his experiments and his research, Gillman also packs in a wealth of useful information." —The Chicago Tribune
"Although Gillman writes that gardening gurus are necessary to dole out knowledge of plants and the traditions that surround growing them, he also winces at all the superstition and half-truths flying around, hence, this terrific book." - Biology Digest 20060501