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Tomato Troubles? It’s Not Your Fault!

By Evelyn Alton, Colorado Master Gardener

2019 was a very challenging year for gardeners. Many vegetables protested in their growth and production; however, the tomato appeared to be the most passive aggressive of them all!

What happened? Tomatoes are very temperature sensitive; while temperatures above freezing may not have visible damage to the plant itself, it does have an impact on flowering, fruiting and ripening. If the nighttime temperatures are below 55°F for three nights in a row, the blossoms opening the next day are unlikely to pollinate. If daytime temperatures are over 90°F before 10:00 a.m., blossoms may abort.

So how do you explain the lovely fruit just hanging on the vine and not ripening? Again, cooler temperatures can cause the plant to focus its energy on roots at the expense of ripening. Temperatures in 2019 were higher and lower than the average, a tomato’s nightmare.

What’s a gardener to do? Here are a few tips to moderate Mother Nature:

  • Watch the weather report and monitor for highs and lows.
  • Provide protection 24/7 and warm the soil prior to planting (a must if planting in May).
  • Plant in June instead of May, select early and mid-season varieties.
  • Select multiple varieties. Include those that set in cooler and hotter temperatures.
  • If temperatures look to be cool, cover your plants (sheet, row cover, basket, etc).

If you need to hasten your tomatoes to ripen or get going, try these:

  • Wake up your tomato plants by fertilizing (if the weather has been cool) to get them going again.
  • Toward the end of season begin to reduce your water by ½ or more.
  • If you need drastic measures with little time left, do a root prune by inserting a shovel 12” from the center of the plant all the way around. Basically, you have just threatened the plant with death and since the plant’s goal is to produce seed, the fruit will ripen.

And most of all? Believe in tomorrow. You know they are worth it.

Evelyn’s favorite tomato picks:

Black from Tula – I am never disappointed with this tomato. Excellent flavor and a very dependable heirloom. Photo:
Stupice (Stoo-PEECH-ka) – an extremely early, cold-tolerant heirloom from Czechoslovakia. Photo:

Pink Berkeley Tie Dye – I will grow this tomato no matter what. It’s that good.
Photo: Wild Boar Farms

Please see the CSU link for additional information on recognizing tomato problems.

2 Responses on “Tomato Troubles? It’s Not Your Fault!

  1. Dala Giffin says:

    Tomato Troubles? Not Your Fault is exceedingly well-written, I enjoyed the read. Evelyn interspersed data and narrative that enticed me to study the figures. I would have liked to know where, specifically, the temperatures were recorded. Are they metro Denver, Front Range, or Arapahoe County? Good to have a suggestion and photo for the cool-hardy tomato.

    1. Evelyn Alton says:

      Hello Dala,
      So sorry for the long wait on the reply as I just ran across this. The temperatures were from Denver. The weather station that provides the temperatures is located at the old Stapleton Airport, now The Urban Farm, through the National Weather Service.

      Thank you for the lovely compliments!
      Evelyn Alton

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