YardMate
English
Download
Knock Out (Rosa 'Knock Out'), whole plant
  • Knock Out — close-up of leaves and flowers
  • Knock Out — seasonal appearance
  • Knock Out in a garden setting

Knock Out

Rosa 'Knock Out'

Easy · Beginner friendly

About Knock Out

Knock Out is the best-selling landscape shrub rose in American history, producing clusters of 3-inch semi-double cherry-red blooms continuously from spring through frost on an incredibly tough 3 to 4 foot rounded bush. Disease-resistant, self-cleaning, and requiring no spraying, it revolutionized American home landscaping after its 2000 AARS win.

  • Low-maintenance
  • Disease-resistant
  • Long-blooming
WATER
Regular
Top inch dry
LIGHT
Full sun
6+ hrs direct
HARDY
Hardy to -30°F (-34°C)
USDA hardiness zones 4–10

How to care for Knock Out

Watering

  • Springevery 7 days
  • Summerevery 5 days
  • Fallevery 10 days
  • Winterevery 21 days

Soil · Rich & loamy

  • Top dressingBark mulch15%
  • Main mixRich loam + compost 3:170%
  • DrainageGravel15%

Use fully finished compost — fresh compost burns roots.

FERTILIZER

Balanced Feed 14-14-14

An even feed covers all three needs at once, keeping leaves, roots and blooms moving together with nothing pushed out of balance.

N33%P33%K33%
  • Nitrogen · Leaves
  • Phosphorus · Roots + Blooms
  • Potassium · Strength
  • Springevery 45 days
  • Summerevery 45 days
Get watering reminders for Knock Out — free on iPhoneDownload on the App Store

At a Glance

  • NativeNorth America
  • Height3–4 ft (0.9–1.2 m)
  • Spread3–4 ft (0.9–1.2 m)
  • Flower colorRed
  • Foliage colorGreen, Bronze
  • SoilLoamy, Well-drained, Rich
  • LocationsYard

Bloom time

BLOOM CYCLE

Peak bloom

May–Sep

J
F
M
A
M
J
J
A
S
O
N
D

Self-cleaning, no deadheading required; prune hard in late winter

Fragrance

LIGHT FRAGRANCE

The flowers have a light scent.

Toxicity

Humans Slight

Unknown toxic principle

Slight

  • Stem
  • Contact

EXPOSURE Touching stems.

EFFECT Pricks from thorns.

NOTE Not toxic; thorns cause mechanical injury.

Safe

EXPOSURE No exposure route is reported.

EFFECT No toxic effect is reported.

NOTE Listed as non-toxic for dogs; avoid eating ornamental plants unless confirmed edible.

Safe

EXPOSURE No exposure route is reported.

EFFECT No toxic effect is reported.

NOTE Listed as non-toxic for cats; avoid eating ornamental plants unless confirmed edible.

Educational information, not medical or veterinary advice. If exposure is suspected, contact a doctor or veterinarian.

DISTRIBUTION

Knock Out · Native
  • Native
  • North America

History

Illustrated historical scene for Knock Out

Rosa 'Knock Out' is a cherry-red shrub rose bred by William J. Radler, an amateur hybridizer and horticulturist in Milwaukee, Wisconsin, over a fifteen-year programme targeting resistance to black spot disease. Conard-Pyle released the cultivar in 2000 from a proprietary cross, and it won the All-America Rose Selections award the same year. 'Knock Out' has remarkable qualities: near-complete resistance to black spot, powdery mildew, and rust; continuous self-cleaning bloom from spring to hard frost without deadheading; cold hardiness into zone 4; and vigorous compact growth needing no spraying.

Within a decade 'Knock Out' and its color sports became the best-selling roses in North American history, with over a million plants sold annually, transforming landscape rose use in public spaces, medians, and home gardens. Bred by William Radler in Wisconsin over 15 years of breeding and introduced by Conard-Pyle in 2000, winning AARS the same year.

The best-selling rose in American history by 2010, it transformed home landscaping by offering disease resistance without spraying, making roses accessible to millions of casual gardeners.

Symbolism & meaning

What It Symbolizes

Knock Out Rose makes visible resilient beauty, a disease-resistant breakthrough that freed countless gardens from black spot and constant spraying. It is also a landscape revolution — the best-selling rose in modern American history, redefining what an ordinary front yard rose could be. A cherry-red shrub that quietly persuaded the country that growing roses did not have to be hard.

  • Resilient beauty — became a disease-resistant rose breakthrough
  • Landscape revolution — best-selling rose in history

Where the Name Comes From

Named 'Knock Out' for its knockout appearance in the landscape and ability to knock out rose disease problems.

Uses & Fun Facts

  • Low-maintenance red shrubs carry color through public beds and home borders
  • Iconic landscape rose with reliable continuous summer bloom
  • Single cherry-red blooms attract bumblebees and native bees

Related plants

More Rosa plants

Plants with similar care

Frequently asked questions

How often should I water Knock Out?

In summer, water about every 5 days; in winter, about every 21 days. Adjust for heat, pot size and drainage.

How much light does Knock Out need?

Full sun: 6+ hrs direct. Watch the leaves — scorching or stretching means the light needs adjusting.

Is Knock Out toxic to cats or dogs?

Pets Safe (Dogs Safe · Cats Safe) Educational information, not medical or veterinary advice. If exposure is suspected, contact a doctor or veterinarian.

Is Knock Out easy to grow?

Yes — it is considered an easy, beginner-friendly plant.

When does Knock Out bloom?

It typically blooms May–Sep in the Northern Hemisphere.

YardMate

Identify any plant in seconds

Snap a photo — YardMate names the plant, diagnoses problems, and reminds you when to water.

Download on the App Store
YardMateIdentify · Diagnose · Remind
Download