This year I went a little crazy with tomatoes. I have close to fifty plants in my garden. I had hoped for a bumper crop that I could freeze and can for future use, but this hasn’t been the best growing season. My Beefsteak tomatoes are ripening at the size of golf balls, Early Girls the size of cherry tomatoes, and cherry tomatoes the size of marbles! What’s causing my crop of Mini-Me-sized produce?
If you were like me, unless you were growing rice this spring, your garden was waaaay too wet to work in. This meant that many of us didn’t get our gardens planted until later in June rather than the typical May planting season for our area. As a result, the heat and lack of adequate rainfall has dwarfed our crops.
If you haven’t added a good layer of mulch to your tomatoes, I recommend doing so immediately to help retain moisture. Tomatoes are 95% water after all. The heat combined with uneven rainfall and other factors has the potential to create the perfect condition for blossom end rot this year.
A Fungus Among Us? … Really?
Contrary to popular belief, blossom end rot is not caused by a fungus, but rather a physiological disorder caused primarily by low concentrations of calcium in the fruit. Calcium is required in relatively large concentrations for normal cell growth. When a rapidly growing fruit is deprived of necessary calcium, the tissues break down, leaving the characteristic dry, sunken lesion at the blossom end. Blossom-end rot is caused when demand for calcium exceeds supply. This may result from low calcium levels or high amounts of competitive nutrient ions in the soil (see tips 1 & 2 below), drought stress, or excessive soil moisture fluctuations which reduce uptake and movement of calcium into the plant, or rapid, vegetative growth due to excessive nitrogen fertilization.
Some Helpful Tips
1. Maintain the soil pH around 6.5. Liming will supply calcium and will increase the ratio of calcium ions to other competitive ions in the soil.
2. Use nitrate nitrogen as the fertilizer nitrogen source. Ammonia-based nitrogen may increase blossom-end rot as excess ammonium ions reduce calcium uptake. Avoid over-fertilization as side dressings during early fruiting, especially with ammonia-based forms of nitrogen.
3. Avoid drought stress and wide fluctuations in soil moisture by using mulches and/or irrigation. Plants generally need about one inch of moisture per week from rain or irrigation for proper growth and development.
4. Foliar applications of calcium, which are often advocated, are of little value because of poor absorption and movement to fruit where it is needed.