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.

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.

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.

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.

prepare garden beds in advance, mix up soil, clean up leaves and cut perennials and grasses before new plantings.

When you should plant what in Colorado

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.

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:

Crop	start seeds indoors	plant seedlings	start seeds outdoors	last date to plant
Arugula	March 8-23	Apr. 13-27	Apr. 6-13	Sept. 8
Asparagus	N/A	N/A	Apr. 20- May 4	May 4
Basil	March 23-Apr. 6	May 18-June 1	May 18-June 1	Aug. 25
Beets	N/A	Apr. 20-May 4	Apr. 6-13	May 18
Bell Peppers	Feb. 23-March 8	May 18-25	N/A	July 14
Bok Choy	March 23-Apr. 6	May 18-25	May 18-25	June 15
Broccoli	March 8-23	Apr. 20-May 4	Apr. 6-13	Aug. 4
Brussels Sprouts	March 23-Apr. 6	Apr. 20-May 4	Apr. 6-13	June 30
Cabbage	March 8-23	Apr. 20-May 4	Apr. 6-13	June 23
Cantaloupes	Apr. 13-27	May 4-18	May 11-18	June 30
Carrots	N/A	N/A	Apr. 6-20	July 28
Cauliflower	March 23-Apr. 6	Apr. 27-May 11	N/A	July 28
Celery	Feb. 9-23	May 11-25	May 4	July 28
Chives	March 8-23	Apr. 13-20	Apr. 13-20	Aug. 11
Cilantro (Coriander)	N/A	N/A	May 4-18	May 25
Collards	March 23-Apr. 6	Apr. 20-May 4	Apr. 13-20	July 28
Cucumbers	Apr. 13-20	May 11-25	May 18-25	July 28
Dill	N/A	N/A	Apr. 27-May 18	Aug. 11
Dry Beans	N/A	N/A	May 18-25	June 30
Eggplants	March 8-23	May 18-25	N/A	July 28
Fava Beans	N/A	N/A	Apr. 6-13	May 18
Fennel	March 23-Apr. 6	May 11-18	May 4-18	July 21
Green Beans	N/A	N/A	May 11-June 1	July 28
Honeydew Melons	Apr. 13-20	May 18-25	May 18-25	July 7
Jalapeño Peppers	Feb. 23-March 8	May 18-25	N/A	N/A
Kale	March 8-23	Apr. 20-May 4	Apr. 6-13	May 18
Kohlrabi	March 23-Apr. 6	Apr. 13-20	Apr. 6-13	May 18
Leeks	Feb. 23-March 8	Apr. 13-27	N/A	June 23
Lettuce	March 23-Apr. 6	Apr. 13-20	Apr. 6-13	May 18
Okra	Apr. 6-20	May 18-25	May 18-June 1	July 28
Onions	N/A	Apr. 6-20	N/A	June 30
Oregano	Feb. 23-March 23	May 11-25	N/A	July 28
Parsley	Feb. 23-March 8	May 11-25	Apr. 6-May 11	July 21
Parsnips	N/A	N/A	Apr. 6-13	June 30
Peas	N/A	N/A	Apr. 6-13	May 18
Potatoes	N/A	N/A	Apr. 6-13	July 28
Pumpkins	Apr. 13-27	May 18-25	May 18-25	June 23
Radishes	N/A	N/A	Apr. 6-13	Aug. 11
Rosemary	Feb. 9-23	May 18-25	N/A	Aug. 11
Sage	March 8-23	May 11-25	N/A	July 21
Salsify	N/A	N/A	May 18-25	June 30
Spinach	March 23-Apr. 6	Apr. 13-20	Apr. 6-13	May 18
Sweet Corn	N/A	N/A	May 18-June 1	July 21
Sweet Potatoes	N/A	N/A	May 18-June 1	June 23
Swiss Chard	March 23-Apr. 6	Apr. 20-May 4	Apr. 13-May 4	May 18
Thyme	Feb. 23-March 8	May 11-18	N/A	July 14
Tomatillos	March 23-Apr. 6	May 18-June 1	N/A	July 21
Tomatoes	March 8-23	May 18-25	N/A	July 7
Turnips	N/A	N/A	Apr. 6-13	Sept. 8
Watermelons	Apr. 13-27	May 18-25	May 11-18	July 7
Winter Squash	Apr. 13-20	May 11-25	May 18-25	June 16
Zucchini (Summer Squash)	Apr. 13-20	May 11-25	May 18-25	Aug. 4

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.

Source: kdvr.com