When to Plant Tomatoes in Colorado?

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Quick Answer: When to Plant Tomatoes in Colorado

Colorado has an optimal growing season of 130 days and experiences its first frost in September end and last frost in May end. The suitable transplanting time should be June but, one should check the expected frost dates and plant accordingly. There must be a two weeks gap between the last frost and transplanting.

This is the ultimate guide on planting and growing tomatoes in Colorado.

It has the average frost dates of Colorado with the best-suited season for transplanting tomatoes. 

Let us get started!

Best Time to Plant Tomatoes in Colorado

The important dates to remember while planting tomatoes in Colorado are –

  • Buying of tomato seeds – February
  • Indoor Planting – March
  • Outdoor Planting – May 15 to May 30. Do not plant after June. 
  • Harvesting – September

Tomatoes flourish if they are grown under their ideal environmental conditions.

The external factors that affect tomatoes are daytime temperature, nighttime temperature, humidity, soil temperature, and rainfall. 

  • A daytime temperature of 75 to 85 degrees F.
  • The nighttime temperature of 55 to 60 degrees F.
  • The humidity of 70-75%.
  • Soil temperature of 65 to 70 degrees F. 
  • Moderate rainfall. 

Check out this video on weather considerations in Colorado –

Before transplanting, check the expected frost dates of your area. 

Here are the frost dates for Colorado –

Table: Frost Dates For Colorado

CityFirst Frost DateLast Frost Date
AguilarSeptember 29May 12
Gunnison Year round riskYear round risk
BrushSeptember 28May 10
RangelySeptember 26May 21

How to Take Care of Tomatoes in Colorado

In this section, I will discuss some of the key aspects of taking care of tomatoes.

Healthy Soil

One of the key aspects to growing great tomatoes is having the right type of soil and soil conditions.

Here are some healthy soil tips –

  • Amend the soil with lots of organic matter, fertilizer, and soluble salts.
  • Check the pH of the soil before planting the roots in it. If required, supplement the soil with eggshells, wood ash, and limestone.
  • Reduce compaction of the soil.
  • Do not work the soil when it is moist
  • Warm up the soil by covering it with fabric, hot caps, or row covers.
  • Mulch the soil immediately after preparing the soil for outdoor planting.

Skating and Caging

Skating and caging can help tomatoes grow by providing support for the plant as it grows. This can help to prevent the plant from tipping over and breaking off its stems.

Caging also helps to protect the tomatoes from pests and animals that may try to eat them.

Here are some tips

  • Dig a wooden stake of a wired cage one to two inches deeper in the soil.
  • Staking and Caging prevent splashing of soil. It supports the plants. For indeterminate variety, staking is a necessary practice.
  • Staking provides ventilation to the plants. It stabilizes the root system of the tomato plant.


Pruning helps tomato plants to get rid of unnecessary plant parts. 

Pruning can help tomatoes grow by allowing more air and light to reach the leaves and fruit, promoting better photosynthesis and preventing fungal diseases.

Here is what you need to do –

  • Through disinfected tools/hands, remove the suckers and bottom foliage of the plant.
  • Put all the fallen parts in a burn pile.
  • Pruning helps in increasing airflow inside the plants and improves sunlight soaking.


Proper watering can help tomatoes grow by ensuring that the plant has enough water to support its growth.

If a tomato plant does not have enough water, it will not be able to produce fruit.

Here are some tips to water tomato plants –

  • Avoid overhead watering on the plant. It makes plants wet and puts them at risk of developing diseases.
  • Avoid wetting the foliage.
  • Water the plants in the morning. Plants will dry quickly under the day Sun. Avoid watering at night.
  • Construct narrow trenches or use a drip irrigation system for an efficient water system. Either way will provide roots with sufficient water quantity without letting any other plant parts get wet.


Transplanted plants demand fertilizer rich in phosphorus. Use water-soluble phosphorus and potassium fertilizer with water. Add the fertilizer to the roots.

Germinated seeds require fertilizer rich in Nitrogen. Add Nitrogen-based fertilizer to the soil trays before sowing the seeds.

Do not overwork with the fertilizer. Add fertilizer three to four times before harvesting.

Best Tomato Cultivars for Colorado

Some popular tomato varieties which you can consider growing in Colorado are – Beef master, Beefsteak, Better Boy, Brandy Wine, Celebrity, Early Girl, Mountain Pride, Patio, Roma, Rutgers, Yellow Pear, Sweet 100, and Shady lady. 

Choose tomatoes that ripen in 60 to 70 days. Colorado has a short growing season so select varieties adapted for the short season. 

Determinate varieties mature early but produce fewer fruits. Heirloom varieties are preferable but they are at higher risk of developing the disease.

A tomato variety must be resistant to-

  • V-Verticillium Wilt
  • F- Fusarium Wilt
  • N- Root-Knot Nematodes
  • TMV- Tobacco Mosaic Virus 

Check out this video on heirloom tomato varieties-


What is the Best Mulch for weed control?

Black Plastic Mulch is a one-season mulch and is easy to use. 

Three inches layers of organic matter such as leaves, hay, and straw are effective in controlling the weed.

How is Trellising better than Staking?

Trellises require little space. The plants are close and produce a larger yield. Like staking, it is suitable for indeterminate varieties.

What is the best location for tomatoes?

An area with a good drainage system and with no big trees around. Plant tomatoes in areas of good sunlight, a proper water system, and heat-absorbing objects around for nights.


I hope this article gave you deep insights on when to grow tomatoes in Colorado.

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