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Epsom salts can worsen tomato problem

Don Kinzler, Growing Together gardening columnist

Q: Can you settle a tomato disagreement? My neighbor says adding Epsom salts to the soil prevents the black rot that frequently happens on the bottom of tomato fruits. I've heard that it doesn't work. Who's right? - Linda M., Hillsboro, N.D.

A: The tomato disorder you mention is called blossom end rot. I'll tactfully avoid choosing sides by simply passing along information from North Dakota State University. The Extension Service addresses the use of Epsom salts in tomatoes by saying "It's time to debunk the myth. Epsom salt doesn't stop blossom end rot - it leads to more of it. Blossom end rot is caused by a deficiency of calcium. Epsom salt contains magnesium sulfate - no calcium at all. Adding Epsom salt to the soil may create more rot since magnesium and calcium ions compete for uptake into the plant. The more magnesium in the soil, the less chance that calcium will be absorbed."

Instead of using Epsom salts, blossom end rot can be minimized by keeping soil moisture more uniform by mulching around plants, avoiding root disruption from close cultivation and avoiding over-fertilization.

Q: How can you tell the difference between a Christmas cactus and a Thanksgiving cactus, other than I suppose the one blooms earlier? - April Hanson, Duluth, Minn.

A: Thanksgiving cactus does tend to respond slightly sooner to the trigger of short days and cool temperatures, although the two cacti often overlap in bloom times. The easiest way to tell them apart is by looking at the stem pads. (They don't really have leaves.) Christmas cacti have rounded pads with smooth edges. The stem pads of Thanksgiving cacti have pointed prongs along the pad edges, which are easily visible. Thanksgiving cacti are frequently mistakenly called Christmas cacti. The care requirements for both plants are similar.

Q: Are strawberry plants supposed to be covered with straw in the fall? We've never covered ours, but I've read that it's recommended. - Brent Wilson, Bismarck, N.D.

A: There are two good reasons for covering strawberries in the fall with straw, leaves or other protective mulch. Strawberry plants are very susceptible to damage from freezing and thawing, which easily happens in winters that lack sufficient snow depth, or when snow disappears in late winter. The heaving effect of freezing and thawing soil can tear roots, damaging or killing plants. Fall mulch keeps plants comfortably frozen, avoiding fluctuations until spring actually arrives.

A second reason for applying fall mulch is to buffer winter's cold, because some of the newer strawberry varieties can be injured at extremely low temperatures. Damage can occur during the occasional "test" winter, and mulching reduces the gamble.

If you have a gardening or lawn care question, email Don Kinzler at All questions will be answered, and those with broad appeal may be published, so please include your name, city and state for appropriate advice.