Gardening in Nevada is always a challenge. At no time does that become more apparent than when we try to grow tomatoes.
Tomatoes require temperatures above 55 F at night but less than 85 F during the day for pollination to occur. If the nighttime temperatures drop below 55 to 60 degrees, no pollen will have developed in the blossoms that open the next morning. If daytime temperatures reach 90 F by 10 a.m., no blossoms that open that morning will set fruit. At temperatures over 104 F, even for only 4 hours, a tomato plant will go into survival mode and abort flowers and fruit. Remember the heat wave we had the last week of July? That may be why your tomato plants haven’t set any fruit.
Tomatoes are the Goldilocks of plants when it comes to nitrogen. Too much and your plant will grow beautiful dark green foliage to 5 feet in height, but not set any fruit. Too little and your plant will be spindly and unable to support a tomato crop.
For those of you lucky enough to have set fruit before the heat wave(s), here are some common tomato afflictions. These are not related to insect pests or disease, but the result of inconsistent irrigation and inadequate plant leaf cover.
Sunscald: Fruits develop yellowish or whitish patches on the side of the fruit exposed to the sun. The patches turn leathery and dry out. Fruit on the same plant that is protected from sun by shade or leaf cover is unaffected. Use row covers to provide shade for small areas. Select varieties next year noted for good leaf cover.
Green or Yellow Shoulders: Fruits develop discolored green or yellow shoulders on otherwise ripe fruits as a result of high temperatures. Similar to sunscald, these areas never ripen and are tough and inedible. Providing shade and choosing varieties for good leaf cover can help prevent the problem.
Radial Cracking: Fruits develop large cracks radiating out from the stem attachment. Cracking occurs on both red and green fruit. Prevent wide swings in moisture by providing even irrigation, and mulching to prevent evaporation of moisture from soil. Select varieties that are more crack-resistant.
Cat-facing: Tomatoes develop that are misshapen with scars and holes at the blossom end of the fruit. The cause is thought to be cold weather during blossoming and perhaps high levels of nitrogen. Avoid setting out transplants too early, and avoid over-fertilizing.
Blossom End Rot: The blossom end of the fruit fails to develop normally, turning black to dark brown. Blossom end rot is usually due to fluctuations in temperature and irrigation. Even though our soils contain plenty of calcium, inconsistent irrigation prevents its transport up to the fruit causing a calcium deficiency.
We’d all like our tomatoes to be pretty and tasty. For all of the tomato problems mentioned, except blossom end rot, the unaffected portion of the fruit remains edible.
Melody Hefner is the Urban IPM and Pesticide Safety Education Program Assistant for the University of Nevada Cooperative Extension. Have a gardening question? Contact a Master Gardener at 775-336-0265 or firstname.lastname@example.org, or visit www.growyourownnevada.com.