Garden guide: When to plant flowers, fruits and vegetables in Colorado

DENVER (KDVR) — Flowers are blooming as the weather in Denver is warming up for the season.

However, the April showers bring May flowers theory doesn’t exactly line up with Colorado’s unique climate and growing conditions.

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Before sowing seeds or planting flowers, fruits, vegetables and herbs, it’s important to know when the best time to do so is.

While Mother’s Day is generally known as the unofficial beginning of planting season in Colorado, there are more nuances to be aware of that can help a garden thrive throughout the season.

Watch the weather

A general rule for gardening is to start planting once the possibility of frost has passed. In Denver, the average last spring frost comes around May 5, according to the National Weather Service. On average, Denver sees its last snowfall of the season around April 28.

While Denver typically sees its last freeze in the first week of May, recent years have seen late freezes in the last couple weeks of May.

Meanwhile, Colorado’s mountain towns and towns in higher elevations can see freezing temperatures into June and sometimes July.

This week, there is a chance for rain showers in the forecast for the first few days of the month, but temperatures will be in the upper 60s for most of the week, possibly reaching 78 on Sunday.

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Things to do before planting

Gardening season begins in late March and runs through October in Colorado, according to Denver Urban Gardens. But before you get to planting, you might want to spend some time playing in the dirt first.

UC Health says the cooler days are a good opportunity to prepare your garden. This can be done by refreshing and replacing soil in pots and gardens. It’s also a good time to add compost to the soil to allow the nutrients to settle in before planting.

Last year, Douglas Long, a garden expert from Country Fair Garden, told FOX31 that it is also good to prepare garden beds in advance, mix up soil, clean up leaves and cut perennials and grasses before new plantings.

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Denver’s climate and elevation classifies as a semi-arid high plane (Zone 6a). The rest of the state, however, varies. The U.S. Department of Agriculture has a map showing the plant hardiness zones in detail. You can use the website and enter your zip code to see what specific zone you are in.

The hardiness zone relates to ground temperatures and how they impact plant health. Most cold-weather crops require a minimum soil temperature of 40 degrees for plants to thrive.

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Almanac.com has a tool where users can input their zip code and find a table suggesting when the earliest and latest planting dates are for optimal results in both the spring and fall.

Here is what the Almanac suggests for planting some common crops in the spring in Denver:

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Other resources have similar tools and tables to use, including Garden.org and Denver Urban Gardens. Colorado State University also has an in-depth vegetable garden guide covering all regions of Colorado.

If you are starting your crops or flowers from seeds, check the back of the seed packet as they often include a guide for planting.

As for flowers, many can handle cold temperatures and are safe to plant sooner, such as trees, shrubs, and perennials like pansies and snapdragons.

Other more sensitive flowers like petunias shouldn’t go into the ground until the threat of a possible freeze has passed.

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