Bob Westerfield is an extension horticulturist for the University of Georgia. Brenda Logan is a technical assistant working with Bob at the Griffin Campus.

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The Top 10 Reasons Your Tomatoes Fail
by Bob Westerfield       #Advice   #Edibles   #Fruit   #Vegetables

Heavy soils and overwatering can lead to fruit cracking as the plants pull in too much water.

If you took a survey of the millions of gardeners in America asking which vegetable is the most popular, no doubt tomatoes would either win the contest or be at the top of the list. Anyone who has ever grown a backyard tomato knows that there is no comparison to the flavor and quality of a freshly grown tomato compared to one purchased at the supermarket. While tomatoes are arguably the king of the vegetable garden, they can be challenging at times because this tropical fruit can be finicky. As one of the state vegetable specialists for the University of Georgia, I receive hundreds of questions each season regarding various vegetable issues. By far, tomato problems exceed those of any other vegetable. Whether that is because they just have more problems or because of how popular they are, they are definitely not easy to grow. Here I will outline what I see as the top 10 issues that can lead to tomato failure in the garden.

Planting too early
A frequent sight in late February after an unusual warm front – Bonnie plant trucks traveling down the road, delivering healthy transplants of tomatoes, peppers and other vegetables to garden centers throughout the South. A few warm days in February or March will send gardeners into a frenzy of buying plants and getting them into the ground. Tomatoes are tropical in nature, and planting them too early can lead to a number of problems. Tomatoes need to be planted based on soil temperatures and not necessarily air temperature. In the South, we can have air temperatures as high as 70 F, and yet the soil will remain quite cool. I prefer to let the soil warm up to a steady 60 to 65 F before I set out tomato plants. Using a soil thermometer, determine the soil temperature before purchasing your tomato transplants. Setting tomatoes out too early has no advantage, and doing so will more than likely lead to some problems. Stunting, tomato leaf curl and catfacing are some common disorders that occur when tomatoes get too cool.

Wrong soil pH
It probably goes without saying, but the pH of your soil is one of the most vital issues to be addressed. The pH directly correlates to the alkalinity or acidity of the soil and greatly affects how well your tomato will be able to absorb nutrients and grow. Typically, I see problems with a low pH more often than a high pH, but neither is conducive to proper growing. Tomatoes do best in a slightly acidic soil with a pH of 6.2 to 6.8. Soil testing at least every other year is imperative to get an accurate handle on your pH level. The pH can be adjusted by adding the proper amount of agricultural lime if it is low or adding sulfur if the pH is too high. Test and adjust your pH several months before the growing season begins to give amendments enough time to affect the soil.

Strong cages or some other form of sturdy support is important to prevent heavy branches from breaking.

Too much nitrogen
I wish I had a dollar for every time someone called and said they have a 10-foot-tall tomato plant that looks great, but with no blooms. I typically respond that they must be using a liquid fertilizer and 99 percent of the time I am correct. The liquid fertilizer itself is not the problem, the high concentration of nitrogen is. While nitrogen is an essential nutrient for growing healthy tomatoes, too much of a good thing can be damaging. Nitrogen’s primary function is to encourage new green growth on a plant, and excessive amounts can “over-encourage” this. Liquid fertilizers are usually high in nitrogen and difficult to calibrate. People tend to use more than necessary, resulting in a lush green plant with no blooms, and therefore, no tomatoes. Fertilize your tomatoes at planting time and don’t fertilize again until the plants have small baby tomatoes, about the size of a dime. You can then feed the plant additional nitrogen without fear of losing the crop.

Improper support for the vine
Many folks growing tomatoes for the first time don’t realize how large they can get as the vines begin to sprawl out in every different direction. Tomatoes, even under normal conditions, can easily reach 4-6 feet tall. When they put out a heavy set of fruit, this adds additional weight to the viny branches. Adequate support in the form of a cage, trellis or some type of string system, must be provided to prevent the tomato from toppling over. Some of the tiny little cages I have seen for sale are just not adequate enough to hold up the weight of a heavy-bearing tomato plant. I prefer to use strong cages made out of hog wire with 4-inch square holes. I pin them into the ground with metal tent stakes to keep them secure. Tomatoes that are not well supported will bend over and break, which will eventually lead to the demise of the entire plant.

Improper watering
In order to produce a successful tomato crop, they must receive sufficient water. Tomatoes do best when the soil is kept evenly moist, neither too dry nor too soggy. Overhead irrigation should be avoided to help prevent potential disease problems that may occur if the foliage stays wet, as well as to avoid watering non-target areas. Hand watering at the base of the plants, soaker hoses or drip irrigation are the best methods to irrigate your plants. Depending on the type of soil you have and how much rainfall received, you may need to irrigate your tomatoes two to four times a week.

Weed competition
Any time you till the soil or dig into it to plant your vegetables, you are more than likely pulling up millions of weed seeds as well. Weeds compete for nutrients and moisture while also looking unsightly in the garden. No matter how you look at it, there is nothing good about a weed and they should be kept out of your tomato garden. Heavy competition from weeds can cause tomatoes to appear lethargic and greatly decrease their yield. Control weeds by using mulch, landscape fabric or labeled herbicides. Keeping weeds out is easier than removing them once they have emerged.

Warm, humid environments are the ideal place for diseases to thrive, so crops in some areas must be watched carefully.

Failure to control diseases
Anyone who grows tomatoes in the South will undoubtedly have to battle an array of diseases that can attack tomatoes. The list of potential diseases is a long one, but failure to pay attention can result in complete failure of the crop. Disease probably takes out more tomatoes each season than anything else. To combat diseases, begin by selecting resistant cultivars. Plant your tomatoes with adequate space around each plant to ensure optimal airflow. At the first sign of disease symptoms, pick off and remove affected foliage. Virus-ridden plants should be completely removed from the garden site. Depending on the disease, chemical controls may be necessary to help stop the spread of the problem.

Failure to control insects
Very similar to diseases, insects love the South almost as much as the people who live here. While the majority of bugs you see in the garden are probably beneficial, there are a small handful of guys that can wreak havoc in the garden. The best way to control insects is to be out in the garden regularly and on the lookout for any signs of attack. Depending on the type of insect, control can include anything from handpicking to organic or chemical options.

Poor soil drainage
Depending on where you live, you may be blessed with dark, loamy soil and no drainage problems. However, many of us have to deal with heavy clay soils that drain slowly and can hold moisture for days. Continuous excess moisture around tomato roots can lead to root rot and other potential diseases. If you are dealing with heavy soils, combat poor drainage by adding a minimum of 4 inches of good topsoil into the mix. Better yet, consider using raised beds – 6-8 inches or higher – to grow your tomatoes.

A lack of calcium in the soil or a calcium deficiency caused by uneven watering can result in blossom-end rot.

Lack of calcium in the soil
If you grow tomatoes, you may experience a physiological problem known as blossom-end rot. Blossom-end rot is due to a lack of calcium, either not enough in the soil or if adequate moisture is not provided, the roots aren’t able to absorb the calcium needed. This causes a black, leathery sunken spot on the blossom side of the tomato, rendering it inedible. It is a fairly common problem and worth mentioning.

There are certainly many more problems a gardener may have when growing tomatoes, but these are the most likely. The good news is that all of these can be prevented or cured to some extent, and by following the advice I have given, you should have plenty of tomatoes for your table, as well as some to give away to your friends.


A version of this article appeared in a March 2014 print version of State-by-State Gardening.
Photography courtesy of Bob Westerfield.


Posted: 02/28/17   RSS | Print


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