How to grow better, bigger tomatoes
As we approach the midpoint of the tomato growing season, let’s review some steps you can take to keep your plants healthy and productive.
Many common tomato diseases are fungal and soil-borne. They include early blight, Septoria leaf spot, late blight, anthracnose fruit rot and buckeye rot. Some are physiological problems, including blossom-end rot, sunscald, fruit splitting, leaf roll and cat-facing. A link with images of common tomato diseases can be found at https://extension.psu.edu/tomato-diseases-and-disorders-in-the-home-garden.
While there is little you can do about what Mother Nature provides by way of rain, humidity and temperature, there are many ways to modify the microclimate around your tomato plants to discourage problems and encourage higher yields.
If you staked your plants, continue to prune the small suckers that grow between the stem and the axil of the leaf. Don’t prune too heavily as this fruit likes to be shaded to reduce sunscald. Heavy pruning can also encourage physiological leaf roll. Do not allow your tomatoes to sprawl on the ground as contact with the soil promotes fruit rot.
As we move into hotter days, supplemental watering may be necessary. Tomatoes need 1-1½ inches of water per week, more if grown in raised beds or containers. Water the soil and not the foliage. Early morning watering is best as it allows for the foliage to dry. Water thoroughly and deeply to encourage deep roots.
What is most critical is to provide consistent moisture. This will reduce the incidence of blossom-end rot as well as splitting. Water stress makes plants more susceptible to early blight, Septoria leaf spot and physiological leaf roll.
If your mulch has “evaporated” by this point in the summer, replenish it with 2-3 inches of straw or bark chips. This will keep weeds down, moderate soil temperature and keep it from drying out. Mulch can also prevent soil-borne pathogens from splashing onto the lower leaves, reducing the spread of fungal disease to the leaves and fruit.
Weed carefully around your plants to reduce competition for moisture and nutrients. Pull weeds when they are small to avoid deep cultivation, which can damage roots. Some weeds related to tomatoes, such as horse nettle, ground cherry and night shade, harbor the same diseases that can affect tomatoes.
A complete fertilizer applied at planting will have provided enough phosphorus (P) and potassium (K) for the season, but tomatoes are heavy feeders and will need supplemental nitrogen (N) applied as a side dressing at least monthly starting after the first fruit has set.
Apply calcium nitrate fertilizer (15.5-0-0) at a rate of 2 pounds per 100-foot row (or 1 cup per 25 feet). Blood meal (12-0-0) is a great option for organic gardeners. Apply it at a rate of 2½ pounds per 100-foot row. Remember, more is not better! While too little nitrogen can result in poor growth and fruit set, too much nitrogen can lead to leaf burn, excess foliage at the expense of fruit and an increased chance for blossom-end rot.
You can use a fungicide as a preventative measure or when the fungal disease is in its early stage. Read the label and follow directions.
As the season winds down, cut back new vegetative growth at the beginning of September. This directs the plant’s energy to the remaining fruit instead of the continued production of foliage.
Pick fruit until the first frost. Then clean up all debris. Clean your stakes and cages. Remind yourself to get your soil tested before the process begins anew next spring.
Here are a few other things you can do to reduce the incidence and extent of these diseases next season:
• Select disease-resistant cultivars.
• Choose a planting site where you haven’t planted tomatoes, eggplant, peppers, potatoes, strawberries or brambles in the past three years.
• Apply a complete fertilizer according to directions and soil test recommendations prior to planting.
• Plant healthy, stocky transplants in full sun.
• Space plants about 2 feet apart when staked, 3 feet when caged to ensure good airflow.
This article was first published in the Pittsburgh Post-Gazette on July 26th, 2019