Brian Maddy County extension agent
June 27, 2014
One of the favorite plants found in gardens worldwide is the tomato.
Ever since the Spanish exported the tomato from the new world to Europe and beyond, tomatoes have become a favorite in many cuisines. At first Europeans were afraid that they were going to be poisoned by consuming tomatoes. Tomatoes are in the same family as the deadly nightshade plant and the leaves are somewhat similar but the fruit is very different.
Most folk’s tomatoes are in the ground and are off and running. At this time you may also begin to notice that there are some problems developing. A few leaves start to disappear or spots and yellow foliage appear.
The new ripening tomatoes start to look a little whitish rather than green. Some of these problems can be headed off at the pass by better preparation, others are weather related.
A common problem is blossom end rot. The bottom of the fruit starts to decay. This looks like a small darkened or water soaked area around the blossom end of the fruit. Usually it becomes inedible plus it’s very unsightly.
It’s caused by a lack of calcium in the fruit. You can have plenty of calcium in the soil and the correct pH and it will still happen. It happens more often when the pH and the calcium level are low.
Calcium in the soil is dissolved and transported up through the plant. Most of us tend to over fertilize tomatoes with nitrogen. This spurs rapid growth in the leaves and the vegetative part of the plant.
When it gets hot and dry, water will be transported to the leaves first. This is where most of the calcium will end up instead of the fruit. Most of this water will be lost to transpiration as the plant strives to stay cool.
Blossom end rot usually shows up in the first cluster of fruit. When fertilizing tomatoes, limit the nitrogen by using a 5-10-10 fertilizer ratio. Ratios such as a 10-10-10 or 13-13-13 may cause problems. The first number is the percent nitrogen in the fertilizer.
Using the spray-on liquid calcium products usually don’t work because by the time the fruit is set, it’s very difficult to get the calcium through the skin of the tomato which is much thicker that the leaves. Ninety percent of the calcium that the fruit requires should be there by the time the tomato is the size of your thumbnail.
As the tomato matures, the bottom shrinks due to the lack of calcium. Now some of the calcium that you spray on may end up in the soil, absorbed by the roots and moved up to the new fruit sets.
You can mix your own calcium chloride (95 percent calcium chloride) solutions at a rate of 4 level tablespoons per gallon of water. Apply every seven to 10 days until you have made three or four applications. This will salvage your remaining crop.
Other preventive measures are to soil test. Then lime and fertilize to test recommendations. The pH needs to be between 6.0 and 6.5. Mix the lime and fertilizer into the root zone prior to transplanting the tomatoes.
Mulch the plants with pine straw, pine bark, compost or newspapers to maintain an even soil moisture. Do not let the plant become water stressed, but don’t over water. Tomatoes need 1 to 1.5 inches of water per week.
Avoid hoeing that may dry out the soil near the plant as well. If necessary, hoe shallow. Be aware that black plastic mulch may cause overheating of the tomatoes as well. The point is not to cause extreme fluctuations in soil moisture that may cause blossom end rot.
Next week we’ll tackle more problems with tomatoes.
Brian Maddy is the ANR Agent for Troup Cooperative Extension. The Troup County Extension office is located at 114 Church St. in LaGrange and may be reached at 706-883-1675, Monday through Friday, 8 a.m. to 5 p.m.