Ask the Experts

All about tomatoes

TOO MUCH SHADE

Question: I have been struggling to grow tomatoes. I planted too many trees and now I think my garden is too shady. Any suggestions?

Answer: Tomatoes are one of the highest light requiring crops we grow. It takes a lot of energy to produce a fruit. Tomatoes need at least 6 hours of full sun each day. When light is lacking the result is poor vine vigor, less flowering, and of course less fruit.

No matter how much water or fertilizer you give the plant it just cannot fully function. Your options are limited to removing the cause of the shade, getting creative about where you grow to take advantage of the available sunlight, check out a local community garden or make more trips to the farmers’ market.

If it makes you feel any better, I am in the same boat. The gardener in me planted too many trees and I am now on my third location. My last resort is removing more grass in the yard to find a sunny spot. But do I want more garden area? I am feeling my age but must have my summer of tomatoes.

LEAF CURL

Question: I have noticed many of my tomato leaves curling or rolling. What causes this to happen?

Answer: There are two common reasons tomato leaves roll or curl. One is the result of a drift of broadleaf herbicides applied to control spring weeds. Tomatoes are extremely sensitive to the vapor drift. The result is a rolling, cupping, and distortion to the foliage. The key here is to look at the vascular system. The veins will be misshapen, unnatural. Drift can come from your own backyard or blow in on the wind from up and down the street. In most cases the issues are secondary, and the plants will recover. Just a delay in production.

Second, a true rolling of the leaf is a natural response to changing weather patterns. A mild wet spring results in rapid top growth at the expense of root development, followed by a period of stress. The plants natural defense is to roll its leaf to reduce moisture loss, which

limits the stress placed on the roots. Natural leaf roll is usually shortterm. As the plant develops stronger roots the symptoms disappear. Since it’s dependent on weather patterns just give it time. Your best defense is even moisture, not overwatering, and reducing stress.

Air movement, mulch and dry foliage lead to healthy tomato plants.

BLOSSOM END ROT

Question: Each summer I get excited to pick my first tomatoes. A lot of the times the bottom of the fruit is black, sunken, and rotted. What is this issue and how do I stop it?

Answer: Your tomatoes have blossom end rot. This problem happens about every year as it is a result of uneven weather patterns in the spring, and cooler wet soils as the plants are developing. Cool soils restrict the uptake of calcium and this deficiency causes the problem. There is not a lot that can be done except provide good care such as even watering. Usually just the first couple of clusters of fruit are affected. The later developing fruit will be just fine.

A few other comments. Since nutrient availability is regulated by

soil pH, test your soil. Make pH adjustments if needed. Proper fertilization is also important, as is even moisture and avoiding deep hoeing around the plant which damages the roots. Adding Epsom salts, eggshells, and other home remedies are not going to help. Epsom salts is magnesium. This is a calcium issue. Eggshells do contain calcium, but they take a long time to break down. They may help in coming years but will make no difference at time of application.

Tomato Septoria leaf spot is a common foliar disease.

FOLIAR DISEASES

Question: Each summer my tomatoes start to lose their lower leaves as they turn yellow. I lose so many it weakens the plant. What can I do?

Answer: We have two common foliar diseases, early blight and Septoria leaf spot. Each start low on the plant and cause dark lesions and yellowing. They work their way up the plant as summer progresses. They are spread from spores on the ground or blow in the wind. Both diseases need a damp leaf to develop.

Culture controls are the best place to start. Space plants to allow air movement, mulch, and avoid wetting the foliage. Try removing the lower leaves as the plant grows in the spring. Eventually remove all the foliage from the base of the plant to about a foot off the ground.

It is best to stay ahead of the disease as spores travel up the plant as summer progresses. When cultural practices fail then applications of fungicides will be needed to slow the development. In the fall clean up the old vines and foliage to help reduce the spread.

Note, if the yellowing starts at the top of the plant the most likely cause is spider mites. Another question to address another day.

NO FRUIT SET

Question: Why do my tomatoes not set fruit on in the summer?

Answer: There could be several reasons. Most likely is our weather patterns. Tomatoes during the summer greatly reduce fruit set when the overnight temperatures remain above 70 to 75 degrees. They also have reduced fruit set when daytime temps are in the mid-90s. We experience these conditions just about every year.

Under hot conditions the pollen often dries up before the flower can be pollinated which reduces set. I know I sound like a broken record, but the best defense is always good care, and even moisture to reduce stress. There are a few varieties on the market bred for better heat set. These include Sunleaper, Sunmaster or Florida 91 to name a few. As the climate warms, we may be facing this issue more often.

DENNIS PATTON Horticulture Agent

Dennis Patton is the horticulture agent for Johnson County K-State Research and Extension. For free information fact sheets, visit www.johnson.ksu.edu, or call the Extension office at 913-715-7000.