Tomato Growing Challenges in Oklahoma

Tomato Growing Challenges

Brian Jervis: Ask a Master Gardener

Sunday, June 24, 2018

This time of year, we get a lot of questions about one of our favorite garden crops: tomatoes. We love our tomatoes, but there are a variety of challenges associated with growing them.

One of those challenges is Septoria leaf spot. Septoria leaf spot is a common fungal disease in Oklahoma. Starting at the bottom of your plant, you will notice leaves with yellow areas that become circular with grayish centers and dark borders. The spores from septoria can be quite aggressive, spreading upward throughout the plant.

When you see this, it’s time to begin a fungicidal spray program of copper fungicide on a 7- to 14-day schedule. This will not cure the infected leaves but will diminish its ability to spread. Infected leaves should be removed.

Also, to minimize exposure and spreading of fungal diseases, tomatoes should not be watered via an overhead sprinkler system, as the splashing water tends to provide a means through which the disease can migrate. Drip irrigation is preferable in most instances.

If you are having problems with fungal diseases, be sure you are rotating your crops. Planting the same crop in the same spot year after year tends to encourage these fungal diseases to develop. However, when rotating crops with tomatoes, do not put peppers, eggplants or potatoes in the same rotation as they all tend to be susceptible to many of the same diseases.

Another common challenge to growing tomatoes successfully is blossom-end rot. Symptoms manifest in an expanding, tan, water-soaked area of the blossom end of the fruit. Blossom-end rot is a complex disorder, which is thought to be caused by a calcium deficiency. However, the solution is not often as simple as adding calcium to the soil.

High temperatures and wind, fluctuating water availability and a little drought stress thrown in (sounds like Oklahoma) create an environment in which you may see blossom-end rot. Somewhat ironically, excessive soil moisture for a long period of time can also contribute to this problem, as it tends to damage the root system and diminish the plant’s ability to uptake calcium. Excessive fertilization with nitrogen can also be a contributing factor.

Just remember, calcium deficiency is rarely a direct cause of blossom-end rot. It is similar to how a fever is an indicator of a problem and not the actual problem. Adding calcium can be of little value if the blossom-end rot is the result of environmental conditions mentioned above.

These are only two of the many challenges we face growing tomatoes. You can find several relevant fact sheets on the topic by visiting the Lawn & Garden page of our website, tulsamastergardeners.org, and then clicking on “vegetables.”

Garden tips

• Vigorous, unwanted limbs should be removed or shortened on new trees. Watch for forks in the main trunk, and remove the least desirable trunk as soon as it is noticed.
• Most varieties of mums are more productive if “pinched back” now. Either pinch off with fingers or cut to remove an inch or so of limb tips above a leaf. This results in the growth of new limbs and a fuller plant. Do not pinch after mid-July or it will interfere with fall blooming.
• Watch for tiny, sap-sucking insects called aphids on roses, perennial flowers, shrubs and vegetables (especially tomatoes). They produce a sticky substance called “honeydew." Many can be dislodged with a hard spray from your garden hose or two applications of insecticidal soap will usually greatly reduce any aphid damage to your plants.
• Crapemyrtles are one of the few shrubs that should be planted in the middle of summer. Growth of new roots of these plants occurs best with summer soil temperatures.

Summer Challenges for Your Gardens

Protecting your garden from summer temps

Allen Robinson: Ask a Master Gardener

Sunday, June 10, 2018

Q: It seems to be getting hotter earlier each year, and 2018 is no exception. What are the most important things I should be focused on to ensure a successful lawn and garden season throughout the summer? Alicia M., Broken Arrow

A: Hot and dry days of summer not only put a stress on people, but also on yards, plants and gardens. Like people, keeping them healthy is the best way to prevent diseases and other problems. Proper weeding, mulching, fertilizing and watering will go a long way to help create and maintain a healthy landscape.

Weeding: Nobody likes to weed, but it’s a necessity. The key is to apply pre-emergent herbicides at the proper time, visit your gardens often and pull weeds as they appear, and to keep gardens properly mulched and lawns properly fertilized. Remember — the best countermeasure to weeds in a lawn is a thick, healthy turf.

Mulching: Mulching protects tree trunks from lawn equipment damage, reduces water loss due to evaporation, keeps the soil cooler in the summer and warmer in the winter, prevents grass and weed growth, adds beneficial organic material to the soil as it decays and, quite simply, looks better. Remember that most plants get oxygen through their roots, not from leaves, and will suffocate without air in the soil. So, a maximum of 2-4 inches of a loose material, such as shredded tree bark, wood chips or compost from your own compost bin, is sufficient. The desirable mulch pattern should look like a doughnut around the trunk, not a volcano.

Fertilizing: Having a soil test conducted is the best way to know exactly what your lawn and gardens need. A test should be done about every three years. In general, Bermuda grass needs about 5 pounds of nitrogen per 1,000 square feet each active growing season, applied between spring and fall. So, a good rule of thumb is to apply 1 pound of nitrogen per 1,000 square feet in each of the five months between and including April and August. Fertilizing after August will increase the chances of spring lawn diseases (e.g. Spring Dead Spot) next year. Fertilize fescue in the spring, then again in September and November. Do not fertilize fescue or any cool-weather grass in the summer.

Watering: Watering more infrequently and longer is preferred over watering often and shorter. This method allows the moisture to go deeper into the ground, thus coaxing roots to do the same. By doing this, your lawn will sustain itself through hot/dry conditions much better. Generally, the equivalent of 1 inch of water per week is sufficient. If it’s very hot and dry, up to 2 inches per week may be necessary. Water early in the morning to avoid heavy evaporation and to give the plants a chance to dry off before nightfall. For gardens, drip irrigation is the most efficient way to water.

Garden tips

• Renovate overgrown strawberry beds after the last harvest. Start by setting your lawnmower on its highest setting and mow off the foliage. Next, thin crowns to 12-24 inches apart. Apply recommended fertilizer, pre-emergent herbicide (if needed) and keep watered.
• White grubs will soon emerge as adult June Beetles. Watch for high populations that can indicate potential damage from grubs of future life cycle stages later in the summer.
• Thatch is a layer of dead and living stems, shoots and roots that pile up on top of the soil at the base of lawn grasses. If it is over ½-inch thick, it should be removed with either a core-aerator or power-rake. Now is the time to de-thatch Bermuda and zoysia. De-thatch fescue, if needed, in the fall.