Knock Out rose

Sun

Full sun, ideally at least 6 hours daily; tolerates light shade but flowers less freely.

Water

Water deeply during establishment and dry spells; established plants tolerate brief drought but flower better with consistent moisture.

Soil

Well-drained loam or clay improved with compost; prefers slightly acidic to neutral soil. Avoid waterlogged ground.

Height

3-4 ft (0.9-1.2 m), sometimes taller if left unpruned

Spread

3-4 ft (0.9-1.2 m)

Flowers

Cherry-red to deep pink-red, single to loosely semi-double flowers in repeated flushes from late spring until autumn frosts.

Foliage

Small, glossy, dark green leaves, often with burgundy young growth; usually deciduous, sometimes retaining leaves in mild winters.

Growth

Moderate to fast

Care needed

Low

• Pollinators
• Heat tolerant
• Disease resistant
• Wildlife
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Very tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1.6 ft (0.5 m)

2. After 1 year

   2.1 ft (0.64 m)

3. After 2 years

   2.5 ft (0.78 m)

4. After 3 years

   3 ft (0.91 m)

5. After 5 years

   3 ft (1.1 m)

   full size

About 4 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Growth rate

Fast

• Water at soil level, soaking the root zone rather than wetting the leaves.
• Apply a rose fertiliser in spring according to the label; avoid heavy feeding late in the growing season.
• Spread 2-3 in (5-8 cm) of organic mulch over the roots, keeping it clear of the stems.
• Allow enough space for the mature spread so air can circulate between plants.
• In exposed zone 5 gardens, mulch the base after the ground begins to freeze to reduce winter injury.

Pruning. In late winter or early spring, as buds begin to swell, remove dead, damaged and crossing stems, then shorten the remaining growth by about one-third to one-half. Deadheading is optional because repeat flowering does not depend on it.

Late winter

In mild climates, prune before strong new growth; in cold climates, wait until early spring.

Spring

Plant when the soil is workable, water thoroughly and refresh the mulch.

Spring

Feed as growth starts and check soft shoots for aphids.

Summer

Water during prolonged dry weather and inspect foliage for disease or beetle damage.

Autumn

Remove fallen diseased leaves and avoid heavy pruning or nitrogen feeding.

Early winter

In the coldest parts of its range, protect the root zone with mulch once sustained cold arrives.

• Plant in repeated groups along a sunny boundary for a long band of red flowers.
• Use as an informal flowering hedge, allowing room for its broad, rounded shape.
• Combine with catmint, salvia and ornamental grasses to soften the shrub's outline.
• Place in a mixed foundation border, set back from paths and windows to accommodate prickly stems.

Garden styles it suits: Traditional, Cottage garden, Formal, Low-maintenance, Farmhouse and Hot border.

Plant it with: Catmint, Meadow sage, Lavender, Hardy geranium, Lady's mantle and Switchgrass.

Wildlife: The open flowers provide accessible pollen for visiting insects, although this cultivated rose offers less wildlife value than many native shrubs. Dense stems can provide some shelter for small birds.

• Black spot: resistance is good but not complete, especially in humid conditions. Remove infected fallen leaves, water at ground level and improve air circulation.
• Rose rosette disease in affected parts of North America: persistent distorted growth, excessive prickles and witches'-broom shoots need investigation. Remove confirmed infected plants, including roots; there is no cure. Normal red young growth alone is not a diagnosis.
• Aphids: dislodge colonies with water and encourage natural predators; use insecticidal soap if an infestation persists, following the label.
• Japanese beetles where established in North America: hand-pick into soapy water, especially early in the morning; avoid placing beetle traps beside the roses.

Not known to be toxic to cats, dogs, horses or people. Leaves, petals and hips are not considered poisonous, but eating plant material may cause mild stomach upset. Prickles can injure skin, mouths and paws; pesticide-treated flowers or hips should not be eaten.

• Double Knock Out rose (Rosa 'Radtko')

  Has fuller, distinctly double red flowers with many more petals than the open flowers of 'Radrazz'.

• Pink Knock Out rose (Rosa 'Radcon')

  Has similar open flowers and growth habit, but the flowers are clear pink rather than cherry-red.

Rosa is the Latin word for rose, while Knock Out is the commercial name under which the cultivar 'Radrazz' is sold.

Propagation. Softwood or semi-ripe cuttings taken in late spring or summer preserve the cultivar. Seedlings will not reliably resemble 'Radrazz'.

Accepted botanical name

Rosa

Sources: GBIF (CC BY 4.0). The care and design notes are LandscapeGPT's own.