Introduction & History

Introduced in 2006, 'Pink Double Knock Out' combined two of the most requested features from the Knock Out family — pink color and double flowers — into a single, supremely garden-worthy package. Registered as 'RADtkopink,' this William Radler creation filled the final quadrant of the Knock Out color-and-form matrix, offering the lush, petal-packed bloom of Double Knock Out in a soft, approachable pink that harmonized effortlessly with virtually any garden color scheme. Where Hot Pink Knock Out shouted, Pink Double Knock Out conversed — its gentle, medium pink tones fitting equally well in formal foundation plantings, romantic cottage gardens, and serene public spaces. The doubled flowers opened like miniature cabbage roses, giving the plant a more traditional, refined appearance while delivering the same ironclad disease resistance and self-cleaning habit that defined the entire Knock Out line. It quickly became one of the most versatile members of the franchise, beloved by gardeners and landscape architects who appreciated its softer aesthetic.

Breeding History

'Pink Double Knock Out' was bred by William Radler in Greenfield, Wisconsin, and introduced by Star Roses and Plants in 2006 under the cultivar name 'RADtkopink.' It emerged from Radler's continuous breeding effort to expand the Knock Out line into every commercially desirable combination of color and flower form. The parentage involves advanced crosses within Radler's disease-resistant breeding lines, combining the double-flower genetics of the Double Knock Out line with the pink color genes. As with all Radler roses, the selection process involved growing seedlings without any fungicide sprays, eliminating every individual that showed disease susceptibility. The result satisfied the demand for a pink rose with the double flower form that many consumers associate with a 'real' rose, all wrapped in the Knock Out promise of zero-spray maintenance.

Flower Form & Fragrance

'Pink Double Knock Out' produces fully double blooms with 18-25 petals, opening from rounded buds into cupped, rosette-form flowers approximately 6-7 cm across. The color is a soft, medium pink — neither the electric hot pink of Pink Knock Out nor the blush of Blushing Knock Out, but a balanced, classic pink that reads as universally appealing. Petals are slightly ruffled, giving blooms a charming, old-fashioned quality. In cool weather, the pink deepens subtly; in heat, it may lighten toward a soft shell pink. Blooms appear in clusters of 3-10, creating a gentle cascade of color. Fragrance is mild and sweet, detectable at close range. The rose is fully self-cleaning, requiring no deadheading.

Garden Design & Uses

'Pink Double Knock Out' is arguably the most versatile Knock Out for garden design, as its soft pink tone harmonizes with virtually every other color in the landscape palette. Use it in foundation plantings, mixed borders, cottage gardens, and formal hedges. It pairs exquisitely with lavender, white peonies, blue delphiniums, and silver-foliaged plants like dusty miller. Plant in groups of 3-7 for romantic garden vignettes. Combine with the red Double Knock Out for a graduated pink-to-red hedge. It works beautifully in memorial gardens, healthcare facility landscapes, and other settings where a soothing, gentle aesthetic is desired. The soft color also photographs well, making it a landscape designer's favorite.

Growth Habit & Hardiness

'Pink Double Knock Out' forms a compact, rounded shrub reaching 90-120 cm tall and 90-110 cm wide, maintaining the classic Knock Out silhouette. Growth is vigorous and naturally tidy, building a dense framework of well-branched canes. Annual new growth averages 30-50 cm. Foliage is medium green with a semi-glossy texture, slightly softer in appearance than the darker-leaved original Knock Out. Autumn foliage shows moderate bronze-burgundy tones. Leaves have 5-7 serrated leaflets with good disease resistance. Thorn density is moderate. The plant is own-root, establishing within two seasons and forming a symmetrical, self-supporting mound that rarely needs corrective shaping.

Climate & Hardiness

'Pink Double Knock Out' is rated for USDA zones 5-10, with cold hardiness to approximately -26°C (-15°F). Some gardeners report success in zone 4b with heavy mulching and favorable microclimates. Heat tolerance is excellent, performing reliably through the hottest summers of the Deep South and Southwest. Humidity tolerance is strong, though the doubled petals may occasionally trap moisture in prolonged wet weather in the most humid climates. The variety handles urban conditions, poor air quality, and reflected heat competently. It is broadly adapted across the continental United States and performs well in most temperate climates worldwide.

Seasonal Care Calendar

Planting & Container Growing

Plant in full sun (6+ hours daily) in well-drained soil of moderate fertility. pH preference is 6.0-6.5, though it tolerates a range from 5.5 to 7.0. Space 90-110 cm apart for hedges, 120 cm for specimens. Dig a generous hole twice the root ball width and plant at the original nursery depth. Amend heavy soils with compost and perlite. Apply 5-8 cm of organic mulch, keeping it away from the crown. Water deeply after planting and maintain consistent moisture during establishment. Once rooted in, the plant is moderately drought-tolerant.

Container Growing

'Pink Double Knock Out' is an excellent container rose, with its soft pink doubled blooms creating an elegant display on patios and terraces. Use a minimum 40-litre pot with drainage holes. Fill with premium potting mix blended with compost and perlite. Water consistently, allowing the top 3-4 cm to dry between waterings. Feed monthly with a balanced rose fertilizer during the growing season. The soft pink color looks particularly lovely in white, cream, or grey containers. Winter protection in zones 5-6 involves insulating the pot or moving to shelter. Feasibility rating: 4/5.

Seasonal Care & Pruning

Spring: Prune back by one-third to one-half in late winter, removing dead and crossing canes. Apply granular rose fertilizer and fresh mulch. Summer: Water deeply once weekly in dry weather. No deadheading needed — fully self-cleaning. Apply a second feeding in late June. Monitor for Rose Rosette Disease and remove any suspect growth immediately. Autumn: Cease fertilizing by mid-August. Enjoy the moderate autumn foliage color. Do not prune. Winter: In zones 5-6, apply 8-10 cm of mulch over the root zone after the first hard freeze. No wrapping needed.

Common Mistakes to Avoid

1. Confusing it with Pink Knock Out and expecting the same vivid hot-pink color — this variety is a softer, more subdued pink. 2. Planting in deep shade, which reduces bloom count and can promote fungal issues even in this disease-resistant cultivar. 3. Over-pruning in autumn, which removes potential bloom wood and can expose canes to winter damage. 4. Ignoring spacing recommendations and planting too densely, which restricts airflow. 5. Expecting strong fragrance — while pleasant, the scent is mild and should not be the primary reason for selection.

Propagation

'Pink Double Knock Out' was protected by US Plant Patent PP18507 (verify current status). Propagation for personal use via softwood cuttings is straightforward when legal: take 12-15 cm semi-ripe cuttings in early summer, apply rooting hormone, and root in a perlite/peat mix under a humidity dome. Expect rooting in 4-6 weeks. Hardwood cuttings in late autumn also succeed. The variety performs well on its own roots without grafting. Commercial propagation is conducted under license using tissue culture and cutting methods. Difficulty rating: Easy.

Diseases & Pests

'Pink Double Knock Out' carries the same outstanding disease resistance as the rest of the Knock Out family. Black spot immunity is excellent, requiring no fungicide intervention. Powdery mildew and rust are rarely encountered. The doubled petals are marginally more susceptible to botrytis in extended periods of cool, wet weather than single-flowered Knock Outs, but this is an uncommon issue. Rose Rosette Disease remains the most significant health threat, as with all Knock Out varieties. Standard pests include aphids on new spring growth, Japanese beetles in midsummer, and occasional spider mites in hot, dry conditions. Thrips may affect individual blooms but are rarely a landscape-wide problem.

Cut Flowers & Exhibition

The soft pink double blooms of 'Pink Double Knock Out' make charming cut flowers for informal and romantic arrangements. Cut in early morning when blooms are half to three-quarters open. Select stems with 2-4 open blooms and buds. Strip lower foliage, recut stems under water, and place in clean water with preservative. The gentle pink color complements white, lavender, and cream companions beautifully. Vase life is 4-6 days. The cabbage-rose form of the blooms adds a romantic, cottage-garden quality to tabletop arrangements and bud vases.

Collector & Exhibition Notes

'Pink Double Knock Out' represents the maturation of the Knock Out franchise, combining the two most requested consumer traits (pink + double) in a single cultivar. For exhibition, it competes in shrub and landscape rose classes. Show preparation involves selecting well-formed sprays with evenly colored blooms and immaculate foliage. Its soft pink tones are distinctive on the show bench, providing a gentler alternative to the bolder red and hot-pink family members. Commercially abundant, its collector significance is as a complete member of the full Knock Out color-and-form range rather than as a rarity.

Comparison with Similar Roses

Compared to Pink Knock Out, the double version has more petals (18-25 vs. 5-7) and a softer, less intense pink color — medium pink versus hot pink. Against Double Knock Out (red), it offers the same flower form in a completely different color for mixed-color landscape schemes. Versus 'The Fairy,' Pink Double Knock Out is more disease-resistant, larger-flowered, and more upright in habit. Compared to 'Bonica' (a classic pink landscape rose), it is more compact, more continuously blooming, and significantly more disease-resistant, though Bonica offers slightly larger individual blooms.

Heritage & Conservation

As a commercially abundant modern cultivar, 'Pink Double Knock Out' faces no conservation concerns. Its heritage significance lies in its role as the culmination of the initial Knock Out family expansion, proving that Radler's disease-resistant genetics could express across multiple color forms without losing performance. Like all Knock Out varieties, it contributes to ongoing discussions about the ecological risks of landscape monocultures and the importance of planting diversity. It is maintained in public garden Knock Out collections and demonstration gardens throughout North America.

Cultural Significance

'Pink Double Knock Out' completed the core color-and-form matrix of the Knock Out franchise, demonstrating that the brand could deliver every combination consumers desired. Its softer pink aesthetic broadened the Knock Out appeal into garden contexts where bold reds and hot pinks were unwelcome, including healthcare landscapes, meditation gardens, and upscale residential settings where subtlety was preferred. The variety's success reinforced the industry-wide shift toward breeding roses for landscape performance rather than exhibition form, cementing the Knock Out family's role as the driving force in modern rose marketing.

Frequently Asked Questions