How to Grow Double Knock Out

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Double Knock Out

Rosa 'Double Knock Out'

shrub

Double Knock Out is a disease-resistant shrub rose known for its prolific clusters of deep red, double flowers that bloom continuously from spring through fall. This low-maintenance variety was developed to improve upon the original Knock Out rose with fuller, more ornamental double blooms while maintaining exceptional hardiness and disease resistance.

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Example Double Knock Out timeline · Pittsburgh, PA (Zone 6b)

Plant Double Knock Out
Around Apr 17

Near Pittsburgh's average last spring frost.
Tend & protect
Late spring–summer

Watering, feeding, and pest-watch reminders.
Harvest Double Knock Out
Around Sep 14

≈ 150 days after planting

Sample dates for Pittsburgh, PA. Sign up to get exact Double Knock Out dates for your own zip code.

Growing Conditions

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Sun: Full sun, 6-8 hours daily minimum; more sun produces more blooms

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Water: Water deeply and regularly, about 1-1.5 inches per week. Soaker irrigation is ideal to keep foliage dry and prevent disease. Reduce watering in winter dormancy.

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Spacing: 24 inches

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Days to maturity: 150-180 days to first significant bloom cluster from planting

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Planting depth: Plant bare-root roses at the bud union level or slightly below; transplants at the same depth as their container

Soil

Type: Well-draining loamy soil with moderate fertility

pH: 6.0-6.5

Amendments:

compost aged manure perlite or coarse sand for drainage

Growing Zones

Find your zone →

Thrives in zones 5-9, performs well into zone 10

5a 5b 6a 6b 7a 7b 8a 8b 9a 9b 10a

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Growth Stages

Establishment

4-6 weeks

New growth emerges with leaflets unfurling; canes are still woody but flexible

Water consistently but do not overwater. Avoid heavy pruning; remove only dead canes and weak growth. Mulch to retain moisture and regulate soil temperature.

Vegetative Growth

6-8 weeks

Plant develops a bushy structure with dense foliage; multiple lateral shoots form along main canes

Begin light pruning to shape plant and encourage branching. Apply balanced rose fertilizer every 4-6 weeks. Monitor for early pest or disease signs.

First Flowering

3-4 weeks

Flower buds form in tight clusters at branch tips; buds develop color and begin to open

Deadhead spent blooms to encourage continuous flowering. Ensure consistent watering during bloom cycles. Begin a regular disease prevention program if needed.

Continuous Blooming

4-5 months (spring through frost)

Plant produces successive waves of deep red, double flowers in clusters throughout growing season; foliage remains healthy and glossy

Continue deadheading. Apply rose fertilizer monthly during bloom season. Monitor for blackspot and powdery mildew despite disease resistance. Pinch back excessively long canes.

Dormancy

3-4 months (late fall through early spring)

Foliage yellows and drops in fall/winter; canes enter dormancy and harden off

Reduce watering significantly. Do not fertilize. Prune in late winter before new growth emerges, removing dead or diseased wood and shaping the plant to 18-24 inches.

Companion Planting

Plan your garden →

Plant with:

Russian Sage Catmint Salvia Lavender Ornamental grasses Coreopsis Daylilies Coneflowers

Avoid planting near:

Black walnut trees (juglone toxicity) plants requiring frequent overhead watering that promote fungal issues competing vigorous shrubs that shade the rose

Common Pests

Hand-pick early morning; use pheromone traps away from roses; apply neem oil or spinosad if population is heavy
Spray with strong water stream; apply insecticidal soap or neem oil; encourage natural predators like ladybugs
Increase humidity and water misting; apply neem oil or miticide if severe
Remove and destroy infected plants immediately; no cure available; maintain healthy plant vigor

Uses

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Rose Petals & Infusions

Culinary

The vibrant red petals can be used to make rose water, floral teas, and edible garnishes for desserts and beverages. Rose petals contain antioxidants and have been traditionally used in culinary and medicinal preparations across cultures. [source]

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Traditional Herbal Remedy

Medicinal

Rose flowers have been used in traditional medicine to support digestive health, reduce inflammation, and promote skin health. Rose hips from some rose varieties are rich in vitamin C and used in herbal teas. [source]

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Garden Landscape & Borders

Household

Double Knock Out is ideal for mass plantings, foundation beds, hedges, and landscape borders due to its compact habit and continuous blooming. Its disease resistance reduces maintenance needs in residential gardens. [source]

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Dried Flowers & Arrangements

Craft

The double flowers dry well for craft projects, potpourri, and pressed flower arrangements. Red roses are traditionally associated with romantic and formal floral designs. [source]

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Pollinator Support

Wildlife

Rose flowers attract bees, butterflies, and other beneficial pollinators, supporting local ecosystem health. While not as prolific a nectar source as single roses, the continuous blooms provide season-long feeding opportunities. [source]

This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.

Harvest Tips

Double Knock Out is grown for ornamental display rather than cutting. Deadhead spent flower clusters by cutting just below the bloom cluster to a healthy outward-facing leaf to encourage more flowering. If cutting for arrangements, harvest in early morning when stems are fully hydrated, cutting with sharp pruners at a 45-degree angle above a leaf node.

Fun Facts

🌱 Double Knock Out was developed by Will Radler, the same horticulturist who created the original Knock Out rose. It was introduced in 2000 and has become one of the most popular landscape roses in North America.
🌱 Unlike many hybrid tea roses, Double Knock Out is known for its exceptional disease resistance to blackspot and powdery mildew without requiring chemical sprays, making it a favorite for low-maintenance and organic gardeners.
🌱 The 'Double' in its name refers to the 45+ petals in each flower compared to the single or semi-double blooms of the original Knock Out, creating a more ornamental, full appearance while maintaining the same hardy, repeat-blooming characteristics.

Gardening Terms

New to gardening? Learn about terms used in this guide:

Deadhead Full Sun Mulch Pinch Back

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