Red tomatoes

Best Planting Times for Tomatoes in Colorado

Planting MethodActivityRecommended Dates
Outdoor PlantingIndoor Seed StartingMarch 1 – April 1
Transplant OutdoorsMay 15 – June 1
Greenhouse PlantingYear-roundAdjust planting based on temperature control in the greenhouse

Planting Conditions in Colorado

Colorado’s climate varies greatly with elevation, but overall, the state experiences a short growing season with potential for late spring and early fall frosts. The state primarily falls within USDA Hardiness Zones 3 to 7.

Sun Requirements

Tomatoes in Colorado need full sun, ideally 6-8 hours of direct sunlight per day. This is crucial due to the shorter growing season, ensuring the plants get enough light to produce a good yield.

Starting Tomatoes Indoors

For areas like Denver (Zone 5b), start seeds indoors from March 1 to April 1. This gives the plants enough time to develop before being transplanted outdoors.

Transplanting Tomato Seedlings

Transplant seedlings outdoors from May 15 to June 1, after the last frost date. Ensure the soil temperature is consistently above 50°F. Space the seedlings 24-36 inches apart, with rows at least 36 inches apart to promote good air circulation and sunlight penetration.

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Useful Tools for Starting Tomatoes Indoors

Using the right tools can save you time and increase your success rate.

Seeds

Quality seeds lead to better germination and healthier plants. Starting with high-quality seeds gives your tomatoes the best chance to thrive from the very beginning.
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Browse Tomato Seeds on Amazon

Planting Trays

Planting trays help you organize your seedlings and ensure they have enough space to grow before you transplant them outdoors. This makes the process more efficient and increases the chances of strong, healthy plants.
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Grow Lights

Grow lights are essential if you don’t have enough natural sunlight. They provide your seedlings with the light they need to grow strong and healthy, even in less-than-ideal conditions.
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Seed Starting Soil

Using light, fine soil specifically designed for seed starting helps young roots establish quickly and promotes healthy growth. It’s an easy way to give your seedlings the best start possible.
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Greenhouse Growing

Greenhouses provide an optimal environment for growing tomatoes by maintaining consistent temperatures, protecting from harsh weather, and extending the growing season. They allow you to control the growing conditions, resulting in healthier plants and higher yields.

Currently, the 8x10x7.5 FT Greenhouse is priced at $999. It’s a great investment for ensuring your tomatoes thrive all year round.
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Check the latest price on Amazon.

Fertilizer

Fertilizer plays an essential role in providing tomato plants with the nutrients they need for robust growth and a plentiful harvest.
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Other planting guides for Colorado:

Any questions on growing tomatoes

Any questions on growing tomatoes? Visit our forum to discuss: Growing Tomatoes

General Care and Maintenance

Watering:

  • Water deeply but infrequently, allowing the soil to dry out slightly between watering to encourage deep root growth.
  • Mulching can help retain moisture and regulate soil temperature.

Fertilizing:

  • Use a balanced fertilizer at planting and apply additional feedings as fruits begin to set.

Pest and Disease Management:

  • Monitor for pests such as aphids and tomato hornworms.
  • Implement preventative measures to manage pests and reduce disease risk.

Harvesting Tomatoes:

  • Harvest tomatoes when they are firm and fully colored. In Colorado, cooler night temperatures can slow down ripening, so be prepared to harvest and ripen indoors if needed.
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