When To Plant Corn In Colorado

Knowing when to plant corn in Colorado is the single most important factor for a successful harvest. Getting the timing right means your corn will have the best chance to grow strong and produce full, sweet ears.

Colorado’s climate is unique, with a short growing season, cool spring soils, and variable weather across its elevations. Planting too early risks frost damage to seeds and seedlings. Planting too late means your corn might not mature before the first fall frost. This guide will help you nail the perfect planting window for your specific area.

For most of Colorado’s Front Range and plains, the optimal time to plant corn is from late April through mid-May. However, this is a general rule. The exact date changes every year based on current weather.

Follow these two simple, natural indicators instead of just a calendar date:

Soil Temperature: Corn seeds germinate best in warm soil. Wait until the soil at planting depth (about 2 inches) is consistently at least 50°F (10°C). A soil thermometer is a cheap and invaluable tool. For faster, more even germination, aim for 55-60°F.
Last Frost Date: Plant after the average last spring frost date for your city. Corn seedlings are very tender and a hard frost will kill them. You can find your area’s average last frost date from your local extension office.

Colorado Planting Zones and Timelines

Colorado’s elevation changes everything. Here’s a regional breakdown:

Eastern Plains (5,000-6,000 ft)

This region has a more reliable warm season. Target planting between April 20 and May 10. Soil warms up relatively quickly here, but watch for late spring storms.

Front Range Urban Corridor (Denver, Boulder, Fort Collins – 5,000-5,500 ft)

The most common gardening region. The safe window is typically May 1 to May 20. Microclimates are common, so always check your soil temp.

Western Slopes & Valleys (Grand Junction, Palisade – 4,000-5,000 ft)

These areas often have milder springs and longer seasons. Planting can often begin in mid-April, especially in warmer, protected valleys.

High Mountain Valleys (Above 7,000 ft)

The season is very short and challenging. You must use short-season corn varieties (under 70 days) and wait until late May or even early June. Using season-extending techniques like black plastic mulch to warm soil is almost essential.

Step-by-Step Pre-Planting Checklist

Choose the Right Variety: Select corn seed suited for Colorado’s short season. Look for “days to maturity” on the seed packet. For areas under 6,000 ft, 70-85 day corn works well. For higher elevations, choose varieties under 70 days.
Test Your Soil: Corn is a heavy feeder. A week or two before planting, test your soil pH and nutrient levels. Corn prefers a pH of 6.0-6.8.
Amend the Soil: Work in 2-4 inches of well-rotted compost or aged manure to improve drainage and fertility. Colorado soils often lack organic matter.
Wait for the Right Conditions: Don’t rush. Check that soil temperature (50°F minimum) and check the 10-day weather forecast for prolonged cold snaps or heavy rain.

How to Plant Corn for Success

Proper planting technique gives your corn a strong start. Here’s how to do it:

Plant in Blocks: Corn is wind-pollinated. Instead of long single rows, plant in blocks of at least 4 rows side-by-side. This ensures the pollen from the tassels can easily reach the silks on neighboring stalks.
Sowing Seeds: Plant seeds 1-1.5 inches deep in heavier clay soils, and up to 2 inches deep in sandy soils. Space seeds 8-12 inches apart within the row.
Row Spacing: Space your rows about 30-36 inches apart. This gives plants room to grow and allows you to walk between them for weeding.
Water Thoroughly: After planting, water the bed deeply to settle the soil around the seeds. Keep the soil consistently moist (not soggy) until you see sprouts, which usually takes 7-14 days.

Early Season Care and Protection

Your job isn’t done after planting. Early season vigilance is key in Colorado.

Frost Protection: Have floating row covers or old sheets ready to drape over seedlings if a late frost is forecasted. Remove them during the day.
Weed Control: Weed carefully around young seedlings. Corn roots are shallow and easily disturbed. A layer of mulch after plants are 6 inches tall can help supress weeds.
Thinning: If you planted multiple seeds per hole (a good insurance policy), thin to the strongest seedling when plants are about 4 inches tall.
Pest Watch: Watch for cutworms and birds. Collars made from cardboard can protect stems from cutworms. Netting or garden fabric can deter birds from pulling up sprouting seeds.

Common Mistakes to Avoid

Planting in Cold, Wet Soil: This is the #1 mistake. Seeds will rot or germinate poorly. Patience pays off.
Ignoring Pollination Needs: A single, long row will result in poorly filled ears due to lack of pollination.
Underwatering at Critical Times: Corn needs the most water during tasseling, silking, and ear development. Drought stress during these stages drastically reduces yield.
Over-Fertilizing with Nitrogen: While corn needs nitrogen, too much early on can cause excessive leafy growth at the expense of ears. Follow soil test recommendations.

FAQ: Planting Corn in Colorado

Can I plant corn in early April in Colorado?

It’s generally too early and risky. Soil is usually too cold, and the chance of a killing frost is very high. Late April is the earliest for the warmest parts of the state.

What is the latest I can plant corn?

For standard varieties, aim to plant by June 1st along the Front Range. After that, the risk of an early fall frost preventing maturity increases significantly. You can push it slightly with ultra-short-season varieties.

How long does it take for corn to grow?

From planting to harvest, it typically takes 60 to 100 days, depending on the variety. Always check the “days to maturity” on your seed packet and count from your planting date.

Can I plant corn from store-bought ears?

It’s not recommended. Most sweet corn from grocery stores are hybrid varieties. Seeds saved from them will not produce true to the parent plant, and the results are often disappointing. It’s best to buy seeds meant for gardening.

What are good corn varieties for Colorado?

Excellent short-to-mid-season choices include ‘Sugar Buns’ (68 days), ‘Quickie’ (64 days), ‘Kandy Korn’ (89 days), and ‘Montana Gold’ (a shorter-season bicolor). For something unique, try ‘Painted Mountain,’ a hardy, short-season flour corn.

By following these guidelines and paying close attention to soil temperature and local weather, you’ll master the art of timing. A successful Colorado corn harvest starts with putting the right seed in the right soil at the right moment. With a little planning, you’ll be enjoying sweet, homegrown corn by late summer.