Gardening

END ROT Brown bottoms on tomatoes signify a calcium deficiency in the soil.

Blossom end rot

Test your soil to determine how much calcium is present

By KATE RUSSELL

Every summer, gardeners discover leathery brown bottoms on tomatoes, peppers, squash and eggplants. This condition is called blossom end rot. People say that blossom end rot is caused by a calcium deficiency, but it’s not that simple.

The internet is filled with treatment solutions for blossom end rot. Most of them include feeding tomato plants with antacids or Epsom salts, sprinkling the soil with crushed egg shells, or watering with powdered milk. These treatments are not recommended. Adding calcium to the soil will help prevent blossom end rot, but only if a calcium deficiency exists. And Epsom salts don’t contain calcium. Contrary to popular belief, calcium deficiency in the soil is rarely what causes blossom end rot in California. Most West Coast soils contain plenty of calcium. There are exceptions and the only way to know for sure is with an affordable, lab-based soil test. And blossom end rot can still occur in soil with abundant calcium.

Blossom end rot appears when plants are not able to absorb and transport calcium to where it is needed. Unlike more mobile nutrients, such as nitrogen, calcium does not move around easily within a plant. Once it stops traveling through the xylem, it stays where it is. This is why calcium deficiency is rarely seen in older leaves.

Calcium is moved through a plant by evapotranspiration, which uses a lot of water. Calcium deficiency can also occur when there is too much nitrogen in the soil, causing plants to grow faster than they can move any available calcium. When plants do not have enough calcium, you may see stunted growth, leaf curling, dead terminal buds and root tips, leaves with brown spots along the edges that spread toward the center, and blossom end rot.

During the fruiting stage, if there is not enough calcium, the cell walls at the bottom of the fruit will collapse. Simply adding calcium to the soil does not correct the problem and foliar sprays are ineffective. Water is needed to transport the calcium into and within a plant. This is why regular, consistent irrigation is key to preventing blossom end rot and other calcium deficiencies.

These same conditions cause similar problems in other garden plants. Carrots may develop cavity spots. Celery may show black heart and stunted central leaves. Bitter pits may appear in apples. Calcium deficiencies often cause leaf tip burn in artichoke, berries, cauliflower and salad greens.

By having your soil tested to find out exactly how much calcium is present and providing regular, dependable irrigation, you can help prevent blossom end rot and enjoy a bigger, tastier harvest.

If you happen to get a few tomatoes with blossom end rot, you can cut out the affected part and eat the rest.