Shrub rose 'Knock Out'
Rosa 'Knock Out' · Rosaceae Popular
The rose that changed rose growing: cherry-red or pink flowers in flushes from late spring to hard frost, on a bushy plant that resists black spot and needs no spraying or deadheading.
- Size
- 4 ft tall, 4 ft wide
- Zones
- 5 to 9
- Light
- Full sun
- Flowers
- Late May to mid October
- Pets
- No toxicity recorded
- Job in a bed
- Anchor
A bed built around shrub rose 'Knock Out'
The planner designed this bed around shrub rose 'Knock Out' when this page was made: a 16 × 8 ft (4.9 × 2.4 m) English border in zone 6, full sun. It chose the other plants from the 966 that suit those conditions, and says below why shrub rose 'Knock Out' stands where it does.
The plants
- 1 Shrub rose 'Knock Out' × 1, red
- 2 Creeping phlox 'Candy Stripe' × 8, pink
- 3 Sea thrift × 13, white
- 4 White mugwort × 4, cream
- 5 Wild quinine × 5, white
- 6 Anise hyssop × 5, lavender
- 7 Ornamental onion 'Purple Sensation' × 5, purple
- 8 Asiatic lily × 5, orange
- 9 Persian fritillary × 4, purple
Why this plant
- The bed's only structure. Shrubs and grasses keep their shape when the perennials die down, and it is the only one here.
- The only red.
Why here
- Anchors a back corner. At 4 ft it is one of the taller plants here, and the tallest close the ends of the bed, where they stand in front of nothing.
- A step in the back row. Next to ornamental onion 'Purple Sensation' (2½ ft): no two neighbours there are the same height, so the back steps up and down like a skyline.
- One plant, alone. A shrub is seen as an object, and needs clear ground around it.
Why now
- In flower for 21 weeks. From late May to mid October.
- Closes the season. For its last four weeks nothing else on the plan is in flower.
Planned as an English border: 8 of the 8 groups (100%) are drifts, longer along the bed than they are deep. The longest in flower is shrub rose 'Knock Out': 21 weeks, from late May to mid October. Creeping phlox 'Candy Stripe' and sea thrift carry the bed through winter.
The planner's own design check: 8 Excellent, 9 Good.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where shrub rose 'Knock Out' goes in a border
At 4 ft it belongs at the back of a bed. In the planner's ten height classes it is moderately tall (3 to 4 ft).
Its job: anchor. A shrub that gives the bed permanent structure. Planted singly, as soon as the front edge is laid; everything else is arranged around it.
It is used as a flowering shrub, not as a traditional rose. The red is strong and constant, so soften it with catmint or grasses. Cut it back by half in early spring.
- Colour from spring to frost
- Hedges and mass planting
- Roses without the work
What to plant with shrub rose 'Knock Out'
Plants recorded as good partners for it, and what each pairing does:
- Catmint 'Walker's Low': in flower together for 16 weeks, from late May; spires rising out of its mound; low enough (24 in) to stand in front of it.
- Salvia 'May Night': in flower together for seven weeks, from late May; spires rising out of its mound; low enough (24 in) to stand in front of it.
- Cranesbill 'Rozanne': in flower together for 18 weeks, from early June; low enough (18 in) to stand in front of it.
Choosing between it and a look-alike? Shrub rose 'Knock Out' vs English rose.
Questions about shrub rose 'Knock Out'
Does shrub rose 'Knock Out' need sun or shade?
Shrub rose 'Knock Out' grows in full sun (6 or more hours of direct sun a day).
It wants ordinary well-drained soil, of average fertility, and a good soak in dry spells.
What zones does shrub rose 'Knock Out' grow in?
USDA zones 5 to 9. It is hardy to zone 5, which means it survives winter nights down to about −10 °F (−23 °C).
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does shrub rose 'Knock Out' flower in my zone?
In zone 5 it flowers late May to mid October. As a spring flower it moves about a week for every zone: earlier where it is warmer, later where it is colder.
| Zone 5 | Late May to mid October |
|---|---|
| Zone 6 | Late May to mid October |
| Zone 7 | Mid May to mid October |
| Zone 8 | Early May to mid October |
| Zone 9 | Early May to mid October |
Worked out from Hopkins' bioclimatic law: spring arrives about four days later for each degree of latitude north, and one zone is roughly two degrees. A warm spring or a cold one moves any garden two weeks either way.
How far apart should shrub rose 'Knock Out' be planted?
3½ ft (100 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 4 ft (120 cm), so a group knits into one patch.
It grows 4 ft (120 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many shrub rose 'Knock Out' plants do I need?
At 3½ ft apart, set out in staggered rows:
- 1 to fill 10 square feet (about 1 m²)
- 4 for a single row 10 ft (3 m) long
- 3 to fill a 4 × 8 ft bed on its own
In a mixed border, plant it as one, planted singly: it is the bed's structure, and everything else is arranged around it.
In the bed above, the planner used one in one group.
Is shrub rose 'Knock Out' poisonous to dogs and cats?
No toxicity is recorded for dogs, cats, horses or people, according to the ASPCA.
"Not toxic" is not "edible": a pet that eats a lot of any plant can be sick.
What flowers after shrub rose 'Knock Out'?
Shrub rose 'Knock Out' is over by mid October. These start as it finishes and carry the same spot on, so it never goes flat:
- Bodnant viburnum 'Dawn': from early November to late December, 10 ft tall.
- Common witch hazel: from mid October to late November, 15 ft tall.
What does shrub rose 'Knock Out' look like in winter?
Shrub rose 'Knock Out' drops its leaves and stands as bare branches. That is when to see its shape, and to prune it if it needs pruning.
More Rosa
- Carolina rose Rosa carolina
- English rose Rosa (English shrub roses)
- English rose 'Gertrude Jekyll' Rosa 'Ausbord' (Gertrude Jekyll)
- English rose 'Graham Thomas' Rosa 'Ausmas' (Graham Thomas)
- Floribunda rose Rosa (Floribunda Group)
- Groundcover rose Rosa (Drift Group)
- Hybrid tea rose Rosa (Hybrid Tea Group)
- Hybrid tea rose 'Peace' Rosa 'Madame A. Meilland' (Peace)
- Redleaf rose Rosa glauca
- Rose 'Bonica' Rosa 'Meidomonac' (Bonica)
- Rose 'Carefree Beauty' Rosa 'Bucbi' (Carefree Beauty)
- Rose 'Double Knock Out' Rosa 'Radtko' (Double Knock Out)
- Rose 'Flower Carpet Pink' Rosa 'Noatraum' (Flower Carpet Pink)
- Rose 'Iceberg' Rosa 'Korbin' (Iceberg)
- Rose 'Julia Child' Rosa 'Wekvossutono' (Julia Child)
- Rose 'The Fairy' Rosa 'The Fairy'
- Rugosa rose Rosa rugosa
- Rugosa rose 'Blanc Double de Coubert' Rosa 'Blanc Double de Coubert'
- Rugosa rose 'Hansa' Rosa rugosa 'Hansa'
- Virginia rose Rosa virginiana
In these guides
- Pet-safe plants for a sunny border
- Shrubs under 4 feet for small gardens
- Long-flowering plants: 12 weeks or more
Zone guides: Zone 5 · Zone 6 · Zone 7 · Zone 8 · Zone 9
In flower in: May · June · July · August · September · October
Every fact on record
- Type
- Shrub
- Size
- 4 ft (120 cm) tall, 4 ft (120 cm) wide
- Plant
- 3½ ft (100 cm) apart
- Height class
- Moderately tall (3 to 4 ft)
- Place in the bed
- Back
- Flowers
- Late May to mid October; open bowls; red, pink
- Leaves
- Medium texture, deciduous; dark green
- Shape
- Rounded, clumping
- Hardy in
- USDA zones 5 to 9
- Light
- Full sun
- Soil
- Average, well-drained
- Water
- Moderate
- Feeding
- Light, in spring
- Family
- Rosaceae
Checked against ASPCA poison lists. Flowering times are for zone 5: later in colder zones, earlier in warmer ones. Toxicity and spread information is a general gardening guide, not veterinary or medical advice, and invasive status varies by region. If a person or pet eats a plant, contact poison control or a vet. Check your local invasive species list before planting anything with a spread warning.