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The best time to plant ornamental grasses in Colorado is in the spring, specifically from mid-April through early June.
This timing gives the roots a full growing season to establish themselves before the intense summer heat and the freezing winter temperatures arrive.
While you can plant ornamental grasses in Colorado during the fall, spring planting is almost always the safer and more successful choice for our unique climate.
In this post, we’ll dig into the specifics of when to plant ornamental grasses in Colorado, how to handle different grass types, and a few extra tips to keep your landscape looking stunning.
Let’s help you get those grasses in the ground at the perfect moment.
When to Plant Ornamental Grasses in Colorado: The Golden Window
The ideal time to plant ornamental grasses in Colorado is during the spring, once the soil has thawed and the danger of a hard frost has mostly passed.
This usually falls between mid-April and early June, depending on your specific elevation and location within the state.
Planting during this window allows the grasses to develop a robust root system while the soil is still cool and moisture is more readily available.
By the time the scorching Colorado summer hits, your grasses will be established enough to handle the stress.
1. Understanding Your Hardiness Zone
Colorado spans multiple USDA hardiness zones, which dramatically affects when to plant ornamental grasses.
If you live in the Front Range or Denver metro area, you’re likely in zones 5b or 6a, so you can start planting in late April.
If you’re in the mountains or high plains, like zones 3b through 4b, you’ll need to wait until late May or even early June for the soil to warm up.
Checking your specific zone is the first step to knowing exactly when to plant ornamental grasses in Colorado for your backyard.
2. The Danger of Fall Planting
Many gardeners in milder states love fall planting, but it’s a risky move in Colorado.
The issue is that newly planted grasses need time to root down before the ground freezes solid.
If you plant ornamental grasses in Colorado too late in the fall, the roots can heave out of the soil during the freeze-thaw cycles we get in winter.
This can kill the plant or leave it severely damaged by the time spring rolls around.
The only exception is if you plant six to eight weeks before the first expected frost, which is usually early September.
3. Soil Temperature Matters More than Air Temperature
When you plant ornamental grasses in Colorado, you should focus on soil temperature rather than just the weather forecast.
The soil needs to be at least 50°F (10°C) for the roots to start growing actively.
If the soil is too cold, the grass will just sit there, potentially rotting in the damp spring ground.
Use a soil thermometer to check the temperature at a depth of about 4 inches before you break out your shovel.
This simple check ensures you’re planting at the right time, not just guessing.
Cool-Season vs. Warm-Season Grasses: Different Timing Needs
Not all ornamental grasses are created equal, and understanding the difference changes when to plant ornamental grasses in Colorado.
Cool-season grasses, like fescue and blue oat grass, actually prefer the cooler temperatures of early spring.
They do most of their growing in the spring and fall, so you can plant them a bit earlier, even in early April.
Warm-season grasses, like switchgrass and little bluestem, wait until the soil is thoroughly warm before they wake up.
For these, it’s best to wait until late May or even early June, since planting them too early just stalls their growth.
1. Plant Warm-Season Grasses in Late Spring
Warm-season grasses are the showstoppers of the fall garden, but they need heat to get going.
If you plant ornamental grasses in Colorado that are warm-season varieties too early, they’ll sulk all summer.
Wait until the overnight lows are consistently above 50°F, which usually happens after Mother’s Day.
This gives them the warm start they crave so they can hit their stride by late summer.
2. Plant Cool-Season Grasses in Early Spring
On the flip side, cool-season grasses can handle a little frost without any trouble.
You can plant ornamental grasses in Colorado that are cool-season types as soon as the ground is workable, even if there’s still a chance of a light freeze.
Their roots will start growing in the cool soil, giving them a head start on the warm-season varieties.
This early start helps them look lush and full by mid-summer.
How to Plant Ornamental Grasses in Colorado for Success
Knowing when to plant ornamental grasses in Colorado is half the battle, but proper planting technique ensures they thrive.
The best time to plant is on a cloudy, cool day to minimize transplant shock.
If you have to plant on a sunny day, do it in the late afternoon so the grasses have the night to recover.
Here are a few key steps to follow when you’re ready to get your hands dirty.
1. Prep the Soil Properly
Colorado soil is often heavy clay or extremely sandy, neither of which is ideal for ornamental grasses.
Amend the soil with compost before planting to improve drainage and add nutrients.
Dig a hole that’s twice as wide as the root ball but no deeper, so the crown of the plant sits right at soil level.
Backfill with the amended soil and water deeply to settle everything in.
2. Water Deeply and Less Frequently
After you plant ornamental grasses in Colorado, watering is critical for the first few weeks.
Water deeply right after planting, then give them a good soak once or twice a week, depending on rainfall.
The goal is to encourage deep root growth, not shallow, weak roots.
Once established, most ornamental grasses are drought-tolerant and need very little supplemental water.
3. Mulch to Protect the Roots
A layer of mulch around the base of your newly planted grasses helps regulate soil temperature and retain moisture.
This is especially helpful if you plant ornamental grasses in Colorado during the warmer end of the spring window.
Use about two to three inches of organic mulch, but keep it away from the crown to prevent rot.
The mulch also helps keep those nasty weeds down while your grasses get established.
What About Dividing and Transplanting?
If you already have ornamental grasses in your yard, the same timing rules apply for dividing and transplanting.
The best time to divide and transplant ornamental grasses in Colorado is in the early spring, just as new growth begins to emerge.
This gives the divided clumps the entire growing season to re-establish before winter.
Avoid dividing in the fall, as the freshly cut roots won’t have enough time to anchor down.
Dividing in spring also reinvigorates grasses that have died out in the center, giving them a new lease on life.
So, When Should You Plant Ornamental Grasses in Colorado?
You should plant ornamental grasses in Colorado in the spring, between mid-April and early June, for the best results.
This timing allows the roots to establish before the summer heat and the harsh winter cold.
Cool-season grasses can go in a little earlier, while warm-season grasses should wait until the soil warms up.
Avoid fall planting unless you’re very confident you have six to eight weeks before the ground freezes.
By following this spring planting schedule, you’ll set your ornamental grasses up for years of beauty and resilience.
So grab your gloves, wait for that soil to hit 50°F, and get those gorgeous grasses in the ground.
Your Colorado landscape will thank you for it.