Lack of calcium in fruit causes blossom end rot

Q: What causes young tomatoes to get a black bottom that turns to rot? — Kristian White, email

A: Blossom end rot is caused by lack of calcium in the fruit when it is small. Calcium is distributed to the fruit via plant sap. But, if the roots become dry, calcium does not make it out to the fruit. Applying calcium (lime) to the soil doesn't help much. Calcium sprayed on the leaves doesn't work, because calcium can't move into the sap that way. The real cause of blossom end rot is inconsistent watering and perhaps overfertilizing. Mulch your plants and keep the soil moist, but not soggy, to keep blossom end rot at bay.

Q: Limes have always been a favorite fruit. When I was growing up, the limes I ate had seeds. They also were not smooth like the limes today. Did the lime of my childhood become extinct? — Camille Mack, Augusta

A: The modern Bearss lime (Tahiti/Persian lime) Citrus × latifolia, does not have seeds because it's a hybrid plant. Kaffir lime, Citrus hystrix, is not common in stores, but it has a bumpy skin like you remember and it has seeds. It's also possible the lime you remember eating was a seedy Key lime. If you plant the seeds of kaffir lime or Key lime in the right conditions, they will sprout and become an attractive indoor plant, but probably never will bear fruit.

Q: I live on a lake and we have beaver problems. What can I plant that they won't be attracted to? They have destroyed azaleas, dogwoods, forsythia, elaeagnus and Knock Out rose. — Kay Fitch, Cumming

A: I think they chew on just about anything. With a lake nearby you'll never eliminate them, so the best you can do is protect your plants. Wrap tree trunks with 36-inch-wide, one-half inch mesh hardware cloth. Loosely surround each tree trunk with a couple of layers of wire and secure the ends so they can't come undone. You also could paint plant trunks with a mixture of one pint of fine sand in a quart of latex paint that's been color matched to the plant bark. Some beavers seem to dislike sand in their mouths.

Q: I have a garden full of plants that I don't know. What resources are there to help identify plants? — Sandi West, email

A: I have a couple of suggestions. First, take a couple of in-focus digital pictures of each unknown plant using your smartphone. Bring them to your local independent nursery on a weekday morning when they are not too busy and ask an employee for help. Second, consider submitting your photos to my Name That Plant website (bit.ly/namethatplant). The group of volunteer plant experts there may be able to suggest your plants' names.