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Garden Help Desk: Getting ready to grow tomatoes this spring

By USU Extension - | Apr 1, 2023

Courtesy Meredith Seaver

Good garden practices and plant care make it more likely to have a nice tomato harvest this year.

We grow a large family garden each year. Usually planting around 100 tomato plants yearly. Last year we lost around 80% of our tomatoes, some varieties it was close to 100%. We grew three popular tomato varieties. Are there any special varieties I should be growing this year to help with our tomato problems?

I’m sorry to say that you and your garden had plenty of company last year. The Utah County Extension office had reports from all over the county and beyond of yellowed and stunted tomato plants that seemed fine early in the season but then declined quite quickly and died within a few days.

So, what was the problem? A disease? Insects? The weather? Bad transplants? More than one cause? Last year there were several possibilities, and many plants had symptoms or evidence of more than one problem.

Tomatoes are susceptible to more than one plant virus and those viruses are carried to the plants by insects or contaminated tools. Aphids, thrips and leafhoppers can all transmit plant viruses and they’re all insects that we have here in our area. Very few of the tomato plant samples sent to the USU Diagnostic Lab tested positive for a virus, though, so a virus can’t be responsible for all the struggling tomato plants last year.

Several fungal diseases can be a problem in our gardens. Poor watering practices, using infected transplants, plant stress caused by temperature extremes, and poor gardening sanitation can all increase the risk of fungal disease. Root rot diseases were found in some of the tomato samples submitted to the diagnostic lab last year.

Courtesy Meredith Seaver

Preventing chilling injury in the late spring is important for having vigorous plants for the rest of the season.

Was the weather the culprit? For some plants, yes. Many parts of Utah Valley had mild weather at the end of April last year and gardeners started setting out their tender transplants and planting their other warm-weather vegetables in early May. Unfortunately, that mild weather was closely followed by a few weeks of cold, wet weather.

Cold, wet soils can slow root development and chilly overnight lows can damage tender plants even though temperatures don’t dip below freezing. The 2022 cold late-spring and early-summer weather was followed suddenly by hot weather that demanded more from our plants than they could keep up with. Some gardeners replanted their damaged tomato plants at the end of the cold spell, getting their new transplants into the garden just as hot weather began.

Part of our hot-weather spell included many days of extreme heat, which can be stressful for even the healthiest of garden plants. For plants already affected by other problems, extreme heat might have been more than they could tolerate.

Did you use rootbound, leggy or poorly colored transplants. Gardeners who needed to replace cold-damaged transplants found that nurseries at the end of our cold spring weather had very few transplants that were still young and vigorous. Unhealthy or struggling transplants become unhealthy and struggling plants. Rootbound transplants often don’t develop the robust root systems our garden vegetables need tolerate stress or produce a good harvest. Poorly colored transplants may have lacked ideal conditions during their last weeks of growth or may have already been infected with a disease.

Not every tomato plant that looked “off” last year went on to decline quickly and die. Some plants only showed rolled leaves, but no stunting or yellowing, and that was most likely a disorder called Physiological leaf roll. Those plants continued to grow, flower, and set fruit when daytime temperatures weren’t too high, despite their appearance.

Courtesy Meredith Seaver

Using 20%-30% shade cloth over tomato plants can reduce heat stress during the summer.

With so many things working against gardeners last year, what can you do to give your garden and plants every advantage this year?

  • Before you do anything in your garden, take the time to clean your tools, tiller and other gardening items that will touch the soil or plants. Wash your gardening gloves if they’re washable.
  • Plant your tomato transplants in a different part of the garden than you used last year.
  • Remove any volunteer tomato plants from seeds left behind last season.
  • Choose good tomato varieties that include heat tolerance and disease resistance in the variety description.
  • Avoid rootbound or overgrown transplants.
  • Don’t be in a hurry to get your transplants out into the garden. Plan for the last half of May and then check the 10-day forecast before planting.
  • Be prepared to protect your plants during chilly nights, if needed.
  • Plan to use 20%-30% shade cloth during the hot part of the summer.
  • Water deeply, but not frequently. Garden soil shouldn’t stay wet or completely dry out.
  • Use drip irrigation, if possible, to reduce risk of soil-born fungi moving in soil water or splashing throughout the garden.
  • Provide adequate, but not excess fertilizer. Over-fertilized and overwatered plants are more susceptible to disease and more attractive to pests.

Fingers crossed for better gardening this year!

Many tomato plants declined and died in Utah County last summer from a variety of causes, but using good gardening practices and healthy transplants will reduce the risk of problems this year.

If a plant doesn't look healthy at the nursery, it won't look better in your garden. Leave sickly plants behind.


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