When To Plant Garlic In Colorado

If you want a successful Colorado harvest, knowing when to plant garlic in Colorado is the most important step. Getting the timing right in our unique climate is what separates a bumper crop from disappointment.

This guide gives you the simple, practical steps for planting, growing, and harvesting garlic here. We’ll cover the best dates, varieties, and techniques tailored for our state.

Garlic is planted in the fall, not the spring. This surprises many new gardeners. Fall planting allows the cloves to establish roots before winter dormancy.

They then explode with growth first thing in spring. This leads to much larger, better-formed bulbs.

The Ideal Planting Window

The goal is to get cloves in the ground so they develop roots but don’t send up green shoots above the soil line before winter. Here’s how to time it:

Best Time: Mid-September through mid-October.
Rule of Thumb: Plant 2-3 weeks after the first fall frost, but before the ground freezes hard.
Soil Temp Clue: Aim for when soil temperature at 4″ depth is about 50°F.

In warmer Front Range areas (Denver, Colorado Springs), you can often plant into early November. In high mountain valleys, aim for early to mid-September. A little later planting is usually safer than too early.

Why Fall Planting Works

Colorado’s cold winters are perfect for garlic. The chilling period is essential for the clove to properly differentiate into a full bulb—a process called vernalization. Without our cold winter, the garlic may not form distinct cloves.

Choosing Your Garlic Type

There are two main types, and your choice matters for our climate.

Hardneck Garlic: This is the champion for Colorado. It’s extremely cold-hardy, produces a delicious central stalk called a scape, and has complex flavors. Varieties like ‘Music’, ‘German Red’, and ‘Chesnok Red’ perform brilliantly here.
Softneck Garlic: Less cold-hardy, better for milder areas. It stores longer and is the type you commonly see braided. It can work in protected Front Range gardens but is less reliable in colder zones.

Always source your seed garlic from a reputable nursery or local grower. Using garlic from the grocery store is often treated to prevent sprouting and may carry disease into your soil.

Preparing Your Planting Site

Garlic needs full sun—at least 6-8 hours daily. The soil must drain well; garlic rots in soggy, clay-heavy earth.

Amend the Soil: Work in several inches of well-rotted compost or aged manure a few weeks before planting. Garlic is a heavy feeder.
Fertilize: Add a balanced organic fertilizer or a specific bulb fertilizer at planting time. Good phosphorus is key for root and bulb development.
Raise Beds: If you have dense clay soil, planting in raised beds is highly recommended to ensure good drainage.

Step-by-Step Planting Guide

Follow these steps for the best results.

Break the Bulb: Carefully break your seed garlic bulb into individual cloves. Do this just before planting to keep the basal plate (the root end) intact. Don’t peel the cloves.
Select the Best: Plant only the largest, healthiest-looking cloves. The bigger the clove, the bigger the eventual bulb. Use smaller cloves for cooking.
Planting Depth & Spacing: Plant cloves pointy-end up, 2-3 inches deep. Space them 6 inches apart in rows that are 12 inches apart. This gives them room to grow.
Mulch Heavily: After planting, water well. Then, apply a 4-6 inch layer of loose mulch like straw, shredded leaves, or grass clippings. This insulates the soil, prevents frost heave, and suppresses weeds.

That’s it for fall! The garlic will quietly root below the mulch and wait for spring.

Spring and Summer Care

Once the weather warms, green shoots will emerge through the mulch.

Watering: Garlic needs consistent moisture, about 1 inch per week, especially during bulbing in May and June. Stop watering about 2 weeks before harvest to let the bulbs cure.
Fertilizing: Side-dress with a high-nitrogen fertilizer in early spring as growth starts. Apply a second dose of balanced fertilizer as the bulbs begin to swell (usually in May).
Weeding: Keep the area weed-free. Weeds compete heavily for nutrients.
Scape Removal: For hardneck garlic, a curly scape will appear in early summer. Cut it off once it makes one full loop. This directs the plant’s energy into the bulb, not the flower. And scapes are a delicious bonus harvest for pesto or stir-fries!

When and How to Harvest

Harvest timing is critical. In Colorado, most garlic is ready from late July to early August.

Watch for these signs, not just the calendar:

The bottom 3-4 leaves turn brown, while the top 5-6 leaves are still green.
The plant begins to look a bit “tired” and leans over.

To harvest, use a garden fork to gently loosen the soil beside the plant and lift the bulb. Do not pull by the stem, as it can break.

Curing and Storage

Proper curing is essential for long storage.

Gently brush off excess soil, but do not wash the bulbs.
Move them to a warm, dry, shaded, and airy place—like a garage, covered porch, or well-ventilated shed.
Hang them in bunches or lay them on a rack. Let them cure for 3-4 weeks.
Once the necks are completely tight and dry, and the outer wrapper is papery, trim the roots and cut the stems.

Store your cured garlic in a cool, dark place with good air circulation. Hardneck varieties typically store for 4-6 months, while softnecks last longer.

Common Problems and Solutions

Poor Bulb Formation

If your bulbs are small, it’s often due to late planting, insufficient winter chill, or not enough sun. Ensure you’re planting at the right time in a full-sun location.

Garlic Rotting in Ground

This is almost always a drainage issue. Amend your soil with compost and consider raised beds for future plantings.

Early Yellowing Leaves

Could be underwatering, a nutrient deficiency (often nitrogen), or occasionally a pest like onion thrips. Ensure consistent watering and proper fertilization.

FAQ for Colorado Garlic Growers

Can I plant garlic in the spring in Colorado?

You can, but results are usually poor. Spring-planted garlic misses the crucial winter chill. It often forms a single large clove (called a “round”) instead of a segmented bulb. Fall planting is strongly recommended.

What is the best mulch for garlic in Colorado?

Straw is excellent because it’s light and insulating. Shredded leaves or grass clippings also work well. The key is applying it thickly (4-6 inches) after planting.

How do I protect my garlic from Colorado’s extreme temperature swings in fall?

The thick mulch layer is your primary protection. It buffers the soil against sudden freezes and thaws, which can cause frost heave and push cloves out of the ground.

My garlic sprouted green tops in late fall. Is that bad?

A little green growth is not a disaster, especially if you planted a bit early. The heavy mulch will usually protect it. The tops may die back in winter, but the clove will regrow in spring. Try to plant a little later next season.

Can I use store-bought garlic to plant?

It’s not advised. Grocery store garlic is often from varieties unsuited for our climate and may be treated with sprout inhibitors. It can also introduce diseases into your garden soil. Invest in quality seed garlic for the best results.

Following these guidelines for when to plant garlic in Colorado sets you up for a succesful harvest. With proper timing, a sunny spot, and good soil, you’ll be rewarded with a homegrown stash of flavorful garlic that stores for months. There’s nothing quite like the satisfaction of pulling up your own perfectly formed bulbs next summer.