The tomato is the most popular home-grown vegetable in the United States.
There are hundreds of varieties, from little grape tomatoes to Amish Paste, a plum variety, to Heirloom tomatoes like Mortgage Lifter. These all have excellent flavor.
Here are some tips on how to keep your tomato plants growing until the end of the season in your garden.
Fertilizer for tomatoes
Tomatoes are heavy feeders and respond well to fertilizer applications. There is no way to know exactly how much and what type of fertilizers you need to apply without having the soil tested by a soil testing lab.
Either too much or too little fertilizer is not good for tomato plants. For example, excess nitrogen fertilizer can result in extremely vigorous vine and leaf growth but little to no fruit production. Too little fertilizer, especially nitrogen, results in slow growth and low yields.
Fertilizers are labeled with their percentage of major nutrients as N-P-K: N is nitrogen, P is phosphorus and K is potassium. The 3rd number, the potassium, supports the plants as they turn from creating foliage to ripening fruit. A preferable one to look for is a fertilizer with close to a 1-2-3 ratio of N-P-K such as 3-4-6 and 9-15-30.
Ripening fruit uses a tremendous amount of calcium (Ca), magnesium (Mg) and potassium (K). If your fertilizer is missing the important nutrients of calcium and magnesium, shop further as there are many choices available in many independent garden centers or online.
Tomatoes, peppers and eggplant all do best when supplied with additional nutrients as they set and develop fruit. Look for soluble fertilizers that are low in nitrogen, but high in potassium. The 1-2-3 ratio of N-P-K applies here.
An application of starter fertilizer at transplanting will help tomato plants grow faster and flower sooner. Starter solutions are water-soluble fertilizers high in phosphorus. Upon setting plants in the garden, apply a liquid starter solution to each transplant at the rate of one cup per plant so that the root ball is completely saturated. Be sure to follow label directions because leaf burning and plant death can result from excessive fertilization.
Watering, fruit problems
Besides lack of proper fertilization, poor fruit set can also be caused by heavy rainfall or temperatures that are either too high (above 90 F) or too low (below 55F).
Tomato plants should be staked or caged shortly after planting.
Fruit problems such as cracking, blossom end rot and uneven ripening can be reduced quite a bit by paying attention to the changing needs of plants with heavy loads of fruit. Blossom end rot looks exactly like it sounds as the flower end of the fruit will turn black and rot. Sometimes these rots occur on the sides as well.
Tomatoes do best when they receive the same amount of water each week. Most gardeners tend to give vegetables too little water. This may be because gardens usually need the most watering during July and August, when gardeners find other demands on their time. Vegetables go through a dry/wet/dry cycle that stops and starts their growth over and over, which reduces the plant’s productivity.
As a general rule of thumb, be sure your garden receives 1 to 1½ inch of water a week from rain and watering systems. Evening out your watering through the use of soaker hose and drip irrigation with timers will improve the plant’s health and quality of the fruit. Fruit that grows evenly will crack less and the nutrients required to create high-quality fruit will be scavenged by the root system.
Diseases and pests
Our generally hot, humid conditions in southcentral Pennsylvania are ideal for the development of fungal and bacterial diseases. It’s easy to miss the most common disease, Septoria leaf spot. It starts on the lowest leaves first but quickly moves upward, killing the leaves. If you see small black spots that don’t brush off, you have Septoria leaf spot. Protectant fungicides work best to control this disease. Chlorothalonil is the active ingredient to look for. The product brand name would be Daconil or Fungonil, and these are readily available. They work pretty well at slowing the development of this disease as well as many other tomato, pepper and fruit diseases.
If you are an organic gardener, look for copper-based and neem-oil-based materials, although research indicates that copper is substantially better at controlling most tomato diseases than neem oil. As this disease progresses up the plant, it gets harder to slow its progress, so treat when you see the first signs.
The next pest that causes summer decline of perfectly healthy tomato plants is spider mites. The tiny pests suck the juices out of the plants, and it gets worse as the weather gets hot and dry. If you see light flecks on the upper leaf surface and small dark spots on the underside of the leaf that move slowly, you probably have mites. To be sure, take a piece of white paper and tap the affected leaves over it. If you see dots that move on the paper, you have spider mites, since dirt and dust do not crawl around.
There are a number of pesticides labeled for spider mite control, but insecticidal soap applied at maximum label concentration weekly will keep this pest at bay with little damage to beneficial insects and the environment. Mites tend to wash off in heavy rains, so thunderstorms will provide some control also.
With a little care, you can keep your tomato plants producing wonderful fruit right up until our first frost. You can extend the season further if you are willing to put floating row covers over the plants on cold nights.
I need to give credit to Steve Bogash, who was a Penn State educator. He specializes in growing vegetables and, because of his expertise, was a great resource for much of the information in this article.