Colorado’s dry conditions demand yarrow be planted during cooler months. Knowing the best time to plant yarrow in Colorado is essential for a thriving, drought-tolerant garden. This guide walks you through the exact timing and steps for success.
Yarrow (Achillea millefolium) is a tough, native perennial that handles Colorado’s intense sun, poor soil, and low rainfall. But timing matters. Plant too late in spring, and heat stress kills young roots. Plant too early in fall, and frost may catch tender transplants.
Let’s break down the ideal planting windows, step-by-step methods, and common mistakes to avoid.
Best Time To Plant Yarrow In Colorado
The absolute best time to plant yarrow in Colorado is early spring, from mid-April to mid-May. A second window opens in early fall, from late August to mid-September. Both periods give roots time to establish before extreme temperatures arrive.
Why Spring Is The Top Choice
Spring planting aligns with yarrow’s natural growth cycle. Soil temperatures warm to 50-60°F, which encourages root development. Cool nights and moderate days reduce transplant shock.
- Soil is workable but not muddy
- Rainfall is more reliable in spring
- Plants have 4-6 weeks before summer heat
- Less need for supplemental watering
In Colorado’s lower elevations (Denver, Colorado Springs, Pueblo), aim for late April. In higher elevations (Boulder, Fort Collins, mountain towns), wait until mid-May. Check your local frost dates—yarrow can handle light frost, but hard freezes below 25°F damage new growth.
Fall Planting As A Backup
Fall planting works well if you missed spring. The key is timing: plant at least 6 weeks before the first hard frost. For most of Colorado, that means late August through mid-September.
- Cooler air temperatures reduce water loss
- Warm soil encourages root growth
- Less competition from weeds
- Plants establish before winter dormancy
Fall-planted yarrow needs consistent moisture until the ground freezes. Mulch lightly with straw or shredded leaves after the first frost to protect roots.
What About Summer Or Winter Planting?
Summer planting is risky. Colorado’s July and August heat can reach 95°F+ with low humidity. New yarrow plants struggle to absorb enough water to keep up with transpiration. If you must plant in summer, choose cloudy days and water deeply every 2-3 days.
Winter planting is not recommended. Frozen ground prevents root growth, and snow cover can smother young plants. Wait for spring or fall.
How To Plant Yarrow In Colorado Soil
Colorado soil is often clay-heavy or sandy. Yarrow tolerates both, but proper preparation makes a difference. Follow these steps for strong establishment.
Step 1: Choose The Right Location
Yarrow needs full sun—at least 6 hours of direct light daily. It grows in partial shade but becomes leggy and blooms less. Pick a spot with good drainage. Avoid low areas where water pools after rain.
- South or west-facing slopes work well
- Rocky or gravelly soil is fine
- Raised beds improve drainage in clay areas
Step 2: Prepare The Soil
Yarrow isn’t picky about soil fertility. In fact, rich soil causes floppy stems. Aim for lean, well-draining conditions.
- Remove weeds and grass from a 2-foot area
- Loosen soil to 8-10 inches deep
- Mix in 1-2 inches of compost if soil is heavy clay
- Do not add fertilizer—yarrow thrives on neglect
If your soil is extremely sandy, add a handful of organic matter to hold moisture. But don’t overdo it. Yarrow’s taproot reaches deep for water.
Step 3: Plant At The Right Depth
Dig a hole twice as wide as the root ball but no deeper. The crown (where stems meet roots) should sit at soil level. Backfill with native soil, pressing gently to remove air pockets.
- Space plants 12-18 inches apart
- Water thoroughly after planting
- Apply 1-2 inches of mulch, keeping it away from stems
Step 4: Water Correctly
New yarrow needs consistent moisture for the first 3-4 weeks. After that, it becomes drought-tolerant. Overwatering is the most common mistake—it causes root rot.
- Water deeply once a week during establishment
- Reduce to every 2-3 weeks after first month
- Check soil moisture 2 inches down before watering
- Use drip irrigation or soaker hoses to avoid wet foliage
Caring For Yarrow Through Colorado Seasons
Once established, yarrow requires minimal care. But seasonal attention keeps plants healthy and blooming.
Spring Care
In early spring, cut back dead stems from last year. Leave 2-3 inches of growth to protect new shoots. Apply a thin layer of compost if soil looks depleted. Do not fertilize with nitrogen—it encourages leafy growth at the expense of flowers.
- Remove winter mulch gradually
- Divide crowded clumps every 3-4 years
- Watch for aphids on new growth
Summer Care
Yarrow blooms from June through September. Deadhead spent flowers to encourage repeat blooming. Leave some seed heads for winter interest and birds.
- Water only during extended dry spells (2+ weeks without rain)
- Stake tall varieties if they flop
- Cut back by half after first bloom for compact growth
Fall Care
In fall, allow yarrow to go dormant naturally. Cut back stems to 4-6 inches after the first hard frost. Leave the basal rosette of leaves intact—they protect the crown.
- Apply 2-3 inches of mulch after ground freezes
- Avoid heavy pruning that exposes roots
- Collect seeds for next year’s planting
Winter Care
Yarrow is hardy to USDA zone 3, so Colorado winters don’t bother it. Snow acts as natural insulation. If you have a warm spell, don’t remove mulch—it prevents freeze-thaw cycles that heave roots.
- Do not water during winter
- Leave seed heads for visual interest
- Check for vole damage under snow
Common Mistakes When Planting Yarrow In Colorado
Avoid these errors to save time and frustration.
Planting Too Deep
Burying the crown leads to rot. Always keep the crown at soil level. If you’re unsure, plant slightly high—yarrow can adjust.
Overwatering
Colorado’s dry air makes people think plants need constant water. Yarrow prefers dry feet. Let soil dry between waterings. Yellowing leaves are a sign of overwatering.
Planting In Shade
Yarrow needs full sun. Even afternoon shade reduces blooming and makes stems weak. Choose the sunniest spot in your yard.
Fertilizing
Rich soil produces floppy, disease-prone yarrow. Skip fertilizer entirely. If your soil is extremely poor, a light compost top-dressing in spring is enough.
Ignoring Soil Drainage
Clay soil that stays wet kills yarrow roots. Amend with sand or gravel, or plant in raised beds. Test drainage by digging a 12-inch hole and filling with water—if it takes more than 4 hours to drain, improve drainage.
Yarrow Varieties For Colorado Gardens
Different yarrow varieties perform better in Colorado’s conditions. Choose based on your space and color preference.
Native Yarrow (Achillea Millefolium)
White or pale pink flowers. Grows 1-3 feet tall. Extremely drought-tolerant. Best for naturalized areas and pollinator gardens.
‘Moonshine’ Yarrow
Bright yellow flowers. Compact, 18-24 inches tall. Silver-gray foliage. Excellent for borders and containers.
‘Paprika’ Yarrow
Red flowers with yellow centers. 2 feet tall. Fades to soft pink as blooms age. Adds bold color to sunny beds.
‘Coronation Gold’ Yarrow
Deep yellow flowers. 3 feet tall. Sturdy stems good for cut flowers. Tolerates poor soil well.
‘Summer Pastels’ Mix
Blend of pink, salmon, apricot, and cream. 2 feet tall. Good for cottage gardens. Blooms from June to frost.
Propagating Yarrow In Colorado
Yarrow spreads easily. You can divide existing plants or start from seed.
Division
Divide clumps every 3-4 years in spring or fall. Dig up the entire plant, separate into sections with roots attached, and replant immediately. Water well for the first week.
- Water the plant a day before dividing
- Use a sharp spade to cut through roots
- Each division should have 3-5 shoots
- Replant at same depth as original
Seed Starting
Yarrow seeds need light to germinate. Sow them on the soil surface in spring after last frost. Press lightly into soil but don’t cover. Keep moist until seedlings appear (7-14 days).
- Start indoors 6-8 weeks before last frost for earlier blooms
- Use seed-starting mix and bottom heat
- Harden off seedlings before transplanting
Yarrow Companion Planting In Colorado
Yarrow attracts beneficial insects like ladybugs and lacewings. It also improves soil health by accumulating minerals. Plant it near vegetables and herbs for natural pest control.
- Good companions: lavender, sage, oregano, echinacea, black-eyed Susan
- Avoid planting near: fennel (inhibits growth)
- Plant along garden borders to deter deer and rabbits
Yarrow’s deep taproot breaks up compacted soil. Use it as a living mulch around fruit trees or in perennial beds.
Troubleshooting Yarrow Problems
Yarrow is generally pest-free, but a few issues can arise.
Powdery Mildew
White powder on leaves. Caused by poor air circulation or high humidity. Space plants properly and avoid overhead watering. Remove affected leaves.
Aphids
Small green insects on new growth. Spray with a strong jet of water or insecticidal soap. Ladybugs usually control them naturally.
Root Rot
Yellowing leaves, mushy stems. Caused by overwatering or poor drainage. Reduce watering and improve soil drainage. Remove affected plants to prevent spread.
Leggy Growth
Tall, weak stems that flop. Caused by too much shade or rich soil. Move plants to full sun and avoid fertilizer. Cut back by half in early summer for bushier growth.
Frequently Asked Questions
Can I plant yarrow in July in Colorado?
July is not ideal due to high heat. If you must, plant in the evening, water deeply, and provide shade for the first week. Expect higher mortality rates.
How long does yarrow take to grow from seed?
From seed to bloom takes about 60-90 days. Start seeds indoors in March for June blooms, or direct sow in May for late summer flowers.
Does yarrow come back every year in Colorado?
Yes, yarrow is a perennial that returns each year. It’s hardy to zone 3 and survives Colorado winters with minimal care.
Should I deadhead yarrow?
Deadheading encourages more blooms. Cut spent flower stems back to a leaf node. Leave some seed heads in fall for birds and winter interest.
Can yarrow grow in clay soil?
Yes, but amend clay with sand or gravel to improve drainage. Yarrow tolerates clay better than most perennials, but standing water causes root rot.
Final Tips For Success
Planting yarrow at the best time to plant yarrow in Colorado sets you up for years of low-maintenance beauty. Remember these key points:
- Plant in early spring or early fall
- Choose full sun and well-draining soil
- Water deeply but infrequently
- Avoid fertilizer and rich soil
- Divide every 3-4 years for vigor
Yarrow is forgiving. Even if you miss the perfect window, it adapts. Start with a few plants and let them naturalize. Within a season or two, you’ll have a resilient, colorful patch that thrives on neglect.
Colorado’s climate challenges many plants, but yarrow is built for it. With the right timing and care, you’ll enjoy blooms from summer through fall, plus the satisfaction of growing something truly tough.
Get your yarrow in the ground during the cool weeks of spring or early fall. Your garden—and the pollinators—will thank you.