Tips for Terrific Tomatoes- and Trivia

Cool summer nights contribute to blossom end rot, a common tomato problem. (Image: Brenda Kennedy, University of Kentucky, Bugwood.org)

Article by, Nicole Sanchez,
Horticulture, OSU Extension Service, Klamath County

Tomatoes- the most popular of all home grown vegetables- are among the most challenging to successfully grow in the Klamath Basin. More than 80% of all home vegetable gardeners try tomatoes, which are also the topic of “Total Tomato Trivia”, the latest joint project of Klamath County Libraries and OSU Extension in Klamath County. Total Tomato Trivia is offered online, Thursday, June 24 at 7pm. In addition to questions about how to best grow tomatoes, Total Tomato Trivia will also cover the broader tomato world: history, botany, culinary uses, folklore around tomatoes. Total Tomato Trivia is easy to play- participants can use a computer or smart phone- and there are valuable prizes involved.

Top three scoring indivuduals or families will receive a generous gift certificate to local garden center Mountain Valley Gardens, and a swag bag compliments of OSU Extension and Klamath County Libraries. Contact the library to register for this fun, educational event, or find more info here: https://klamathlibrary.org/library-events/gardening-trivia-competition-total-tomato-trivia.

Tomato- related challenges in the Klamath Basin are usually, at least in part, a result of our cool summer nights. Tomatoes are tropical plants, and do not react well to temperatures under 50-55F. Even in the warmest summer months, nights in the Klamath Basin often dip into the 40’s and 50’s. If there is any visible sign that tomatoes are struggling with cool nights, it’s a purple cast to leaves or the veins in the leaves. Observant gardeners may see the purple color and associate it with a phosphorus deficiency- but that’s not the whole story.

One cause of phosphorus deficiency in tomatoes is cool soil. Tomatoes don’t just prefer warm air- they also perform best in warm soil. For tomatoes, “cool soil” is anything under 50-55F. Even when phosphorus is available, tomatoes can’t access it when the soil is too cool. A more common response, and one more difficult to recognize, is tomatoes that just sit in the soil and don’t seem to grow or do anything. Later in the season as fruits develop, they take agonizingly long to ripen. Every night that tomatoes are subjected to temps under 50F, development is stunted- though there may be no easily recognizable sign that something is wrong.

Gardeners can “warm the soil” to create happier tomato habitat. A heavy mulch of organic material, for instance of bark nuggets or shredded bark, is one option. Covering the soil with black plastic is very effective. Using season extension like a greenhouse, high tunnel, or covering plants to trap afternoon heat near the plant also helps. Consider microclimate: can tomatoes be planted near a stone wall, or near the house where they are in a protected spot? A few local Master Gardeners have success growing tomatoes in huge, wheeled containers in the driveway. Out into the sun each day, the plants are rolled into the warm garage at night.

Blossom end rot, another common tomato problem in our area, is also in part connected to cool summer nights. Often considered a disease of tomatoes, Blossom end rot is actually a physiological problem associated with lack of calcium during fruit development. Calcium moves slowly through the plant, and is not taken up through the fruit itself, so don’t fall for sprays meant to apply calcium to developing fruit. If blossom end rot has been an issue previously, calcium can be applied at planting time so it is available throughout the plant’s development. More importantly, keep soil warm and water tomatoes early in the day.

Garden references typically suggest early morning or evening watering for vegetable gardening, either being preferable to watering in the middle of the day. In the case of tomatoes and Klamath’s quirky growing conditions, watering in the afternoon is less desirable. Here’s why: when temperatures are rapidly declining, as they tend to do on Klamath summer nights, tomatoes aren’t very efficient at using either water or calcium. Tomatoes only watered late in the day may not be able to properly move calcium through the plant, even when it’s abundantly available in the soil.

The dry summers of the Klamath Basin do offer some advantages for growing tomatoes: the most challenging tomato diseases- like early blight, late blight, anthracnose, Verticillium wilt- are far more common in humid climates with ample summer rainfall. In the Basin, these problems are most often associated with overhead watering.

The challenges around growing ripe tomatoes are not trivial- although some of the answers to questions in Total Tomato Trivia are possibly found among the tips in this article. Home gardeners can minimize our most common challenges by keeping their tomato plants warm on cool summer nights.  Join us to test your tomato knowledge on June 24!