Tomatoes, the tasty fruit

c-potting shed tomatoplant




Nothing tastes more like summer sunshine than the sweet tang of a just picked home-grown tomato. I don’t believe anything you buy in the grocery store, even those grown on the vine or hydroponically, can compare to home-grown. If you are a tomato lover this is one vegetable (although it is technically a fruit) that I would recommend you grow in your garden –even if you grow no others.

Scientifically, a tomato is technically a fruit. That is because it is formed from the ovary at the base of the flower and it contains seeds, much like apples, oranges, cherries and other fruits. We refer to the tomato as a vegetable because of the way we cook with it. It is usually used in savory dishes like salsa or tomato sauce rather than sweet dishes, and because in 1893, the United States Supreme Court declared that tomatoes fell under the category of vegetable and therefore were subject to import tariffs that applied to vegetables but not to fruits.

The tomato (Solanum Lycopersicum) is a member of the nightshade (Solanaceae) family, and like eggplants and peppers, is a heat seeking plant. All are related to the potato. The tomato originated in the South American Andes and its use as a food began in Mexico and spread throughout the world after the colonization of the Americas.

Tomatoes can be determinate or indeterminate in growth type. Determine plants stop growing once they flower and the fruit ripens in a determinate period of time. Indeterminate plants continue to grow, flower and ripen fruit throughout the growing season. While it might seem to be ideal to have continuous crop of tomatoes throughout the season these plants can become quite large and unmanageable and will need to be staked or grown on a trellis.

Growing tomatoes is relatively simple provided you have the right growing conditions and use good cultural practices. One tomato plant, properly cared for, can yield 10-15 pounds of fruit. Unfortunately, without attention to detail, there are a number of fungal diseases and non-parasitic disorders that can affect the yield and the quality of your fruit.

Two of the most common fungal diseases are Fusarium and Verticillium that are two soil-borne fungi that can affect the leaves of tomato plants. Fusarium begins with the yellowing and wilting of the oldest leaves of the plant and can occur anytime during the growing season. If the plant is infected early on, it can result in complete defoliation and little or no fruit being produced. Symptoms of Verticillium usually appear in mid-August when the lowest leaves begin to yellow, wilt and fall off. The fruit is usually well established by this time, but if the plant is substantially defoliated the fruit may be damaged by over exposure to the sun. Fusarium and Verticillium may occur year after year because these fungi can overwinter in the soil.

Another disease that affects the leaves of tomato plants is Septoria leaf spot. This is another fungus, whose spores can survive the winter on plant debris or on some perennial weeds left in the garden. First symptoms are round yellow spots on the lower leaves shortly after the fruit is set. These spots grow and turn gray or black and eventually small black fruiting bodies produce spores, which cause infection further up the plant. Heavily infected leaves turn yellow, then brown and drop. Many of these tomato diseases have similar symptoms making diagnosis of the particular disease difficult.

Best practices for preventing and/or controlling diseases in your tomato plants are:

  • No overhead watering. Water your plants at ground level to prevent soil that may contain spores or fungi from splashing onto the leaves. Water at the base of the plants in the morning before the temperature and humidity rises.
  • Mulch the soil to prevent soil from splashing onto the leaf. Mulching will also keep the soil temperatures down and prevent weed germination.
  • If a disease does develop on your tomato plants take precautions to prevent the disease from spreading or reoccurring on next year’s plants:
    • Remove all diseased plant material from the plant before it hits the ground. This prevents the fungus or spores from entering the soil.
    • Cage or stake your plants to provide good air circulation and keep the leaves and fruit off the ground.
    • Don’t grow your tomatoes in the same spot more than once every three or four years.

Non-parasitic disorders are ones that are not caused by fungi, viruses or bacteria.  One of the more common disorders of tomatoes is blossom end rot, indicated by a brown and leathery spot at the blossom end of the fruit. Blossom end rot can be attributed to a calcium deficiency, large fluctuations in moisture, too much nitrogen fertilizer or root pruning. Periods of hot dry weather followed by excessive rain are a common cause of blossom end rot in the home garden. Make sure you water your plants regularly during dry periods. And avoid cultivating the soil around them to avoid pruning the roots.

Sunscald is another common disorder of tomatoes. It is characterized by a flattened gray spot with a papery surface usually on the side of the fruit facing the sun. Sunscald usually occurs on a plant that has suffered a loss of foliage, which would normally shade the fruit. To prevent sunscald of tomatoes on a plant that has lost its foliage, try to provide some shade to the fruit.  Tomato fruit do not need sunlight to ripen. The fruit actually ripens from the inside out. Mature fruit continues to ripen and change color even after it is harvested. If you are unable to shade your tomatoes from sunscald it may be preferable to pick the mature ones and ripen them indoors.

With good cultural practices we should be able to grow a bounty of tomatoes year after year.