Tomato Troubles

     "I had these really beautiful tomatoes,” the caller told me, “but when I went to pick them there was a black scab on the bottom. What is this, and can I still eat the tomatoes?” 

     This was a typical August call into GardenLine, my weekly radio program. At one time or another most gardeners will have a similar experience. The dark spot is a condition called "blossom-end rot." It is the result of insufficient calcium in the developing fruit, but the cause is seldom lack of calcium in the soil. The problem usually occurs because the plant can't absorb calcium because something has disturbed the roots.

     Long periods where the soil is either too wet or too dry will cause blossom-end rot. If the roots have dried or are waterlogged, they can't take up the calcium that the plant needs to produce perfect fruit. Excessive fluctuations in soil moisture can also result in that ugly brown scab. Tomatoes grown in containers that are allowed to get dry before being soaked may also develop blossom-end rot.

     Another potential cause? Roto-tilling or cultivating too close to the plant. Tilling the soil too deeply, or too near the stem will cut up the root system and this inhibits the plant's ability to absorb nutrients.

     To prevent blossom-rot, keep the soil evenly moist but not wet. A layer of mulch around the plant can help; dried grass-clippings, chopped leaves or thick layers of hay work well. If you control weed growth using a hoe or roto-tiller, stay at least two feet away from the tomato stem. 

     And if you do have blossom-end rot this season, take heart. The first fruits are most severely affected, and the tomatoes are still edible. Cut off the ugly parts, garnish with homegrown basil, and repeat the gardeners mantra: "Next year, it will all be perfect."