Double Knock Out rose

Sun

Full sun, ideally at least 6 hours daily; light afternoon shade can help in very hot climates.

Water

Water deeply during establishment and prolonged dry spells, letting the soil surface dry slightly between waterings. Avoid constantly wet roots.

Soil

Fertile, well-drained soil, ideally slightly acidic to neutral; tolerates clay if drainage is adequate.

Height

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

Spread

3-4 ft (0.9-1.2 m)

Flowers

Repeated flushes of double cherry-red flowers from late spring into autumn, often until frost.

Foliage

Glossy, dark green, compound leaves with toothed leaflets; young growth often has reddish tones. Stems bear sharp prickles.

Growth

Moderate to fast once established.

Care needed

Low

• Heat tolerant
• Disease resistant
• Wildlife
• Low allergen

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

Difficulty

Easy

Toughness

Fairly 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 frequently sprinkling the surface.
• Spread 2-3 in (5-8 cm) of organic mulch over the root area, keeping it clear of the stems.
• Apply a rose fertiliser in spring as growth begins, following the label; avoid late-season nitrogen in cold climates.
• Space plants for their mature width so air can move through the foliage.
• In exposed zone 5 gardens, protect the crown with an insulating mulch after the ground begins to freeze.

Pruning. In late winter or early spring, as buds swell, remove dead, damaged and crossing stems, then reduce the remaining growth by about one-third to one-half to maintain a compact shape. Deadheading is optional; use clean tools and wear thorn-resistant gloves.

Late winter

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

Spring

Plant into workable, well-drained soil, water thoroughly and renew mulch.

Mid-spring

Feed established plants as leafy growth develops.

Summer

Water deeply during dry weather and inspect new growth for aphids, mites and unusual distortion.

Early autumn

Avoid hard pruning and stop nitrogen feeding in cold-winter regions so growth can mature.

Late autumn

Remove fallen diseased leaves; add crown protection in exposed cold sites once the soil starts freezing.

• Plant in groups along a sunny front boundary for repeated red colour through the growing season.
• Use as an informal flowering hedge, allowing enough width for mature plants rather than clipping tightly.
• Combine with catmint, salvia or lavender to soften its outline with blue-purple flowers.
• Place among evergreen shrubs in a mixed border for summer colour against a permanent green backdrop.

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

Plant it with: Catmint, Hardy salvia, Lavender, Cranesbill geranium, Lady's mantle and Ornamental onion.

Wildlife: The dense double flowers offer less accessible pollen than single roses, so this is not a strong choice for pollinator planting. Foliage can support insects, and the branching shrub provides some cover for small birds.

• Black spot: dark leaf spots and yellowing can occur despite its resistance. Water at soil level, improve airflow and remove infected fallen leaves.
• Rose rosette disease: in affected parts of North America, persistent distorted red growth, excessive prickles and witches'-broom shoots need prompt assessment. There is no cure; remove infected plants, including roots, rather than pruning out individual shoots.
• Aphids: clusters on soft shoots can distort buds. Dislodge with water and encourage natural predators; use insecticidal soap if necessary, following the label.
• Japanese beetles: where present in North America, adults chew flowers and skeletonise leaves. Hand-pick into soapy water; avoid placing beetle traps beside the roses.

Not known to be toxic to cats, dogs, horses or people. Chewing leaves or flowers may cause mild stomach upset, while sharp stem prickles can injure mouths, skin and eyes; pesticide-treated plants should not be eaten.

• Knock Out rose (Rosa 'Radrazz')

  The original Knock Out has open, single cherry-red flowers with visible yellow stamens, rather than the fuller double flowers of 'Radtko'.

• Pink Double Knock Out rose (Rosa 'Radtkopink')

  It has a similar double flower shape and shrub habit, but the flowers are bright pink rather than cherry-red.

Double Knock Out refers to its fuller, double flowers within the Knock Out rose series; 'Radtko' is its registered cultivar name.

Propagation. Softwood or semi-ripe stem cuttings preserve the cultivar; seedlings will not reliably match it. Check local plant breeders' rights or patent restrictions before propagating.

Accepted botanical name

Rosa

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