Rose BushesA Grower's Guide to Roses
Knock Out Rose

White Knock Out

Pure white landscape rose.

A white member of the knock out roses group, White Knock Out is grown for its long succession of blooms and its resilience in the garden. Below you'll find a full profile of White Knock Out — its characteristics, how to grow it, where to use it in the garden, and answers to the questions gardeners ask most.

About White Knock Out

As one of the knock out roses, White Knock Out carries the traits gardeners look for in the group — single to double flowers held in generous clusters. As a self-cleaning landscape rose it drops its own spent flowers, so deadheading is optional and one hard prune a year keeps it shapely.

In flower, White Knock Out is white and fills the plant with bloom in wave after wave, carrying a light, pleasant fragrance. It is hardy across USDA zones 5-11, so it suits a wide range of gardens with the right seasonal care.

Characteristics and form

White Knock Out makes rounded, bushy, self-supporting shrub, typically around 3 to 4 feet tall and 3 to 4 feet wide. The blooms are single to double flowers held in generous clusters, medium in size, set against glossy, dark, and notably disease-resistant foliage. Knowing a rose's habit and mature size is the key to placing it well: give White Knock Out room to reach its full spread without crowding its neighbors, which also keeps air moving through the plant and disease at bay.

How to grow White Knock Out

Plant White Knock Out where it will get at least six hours of direct sun a day in fertile, well-drained soil with good air movement around it. In cold climates, set the graft union — the swollen knob where the variety joins the rootstock — at or just below the soil line; in mild climates, keep it at soil level. Once planted, water deeply and less often to encourage deep, drought-resistant roots.

  • Light: Full sun, six hours or more; morning sun is best because it dries dew early and limits disease.
  • Soil: Rich and well-drained, slightly acidic at about pH 6.0–6.5. Improve heavy or sandy soil with plenty of compost before planting.
  • Water: Deep, infrequent soakings at the base rather than frequent light sprinkling; more in heat, sandy soil, or containers.
  • Feeding: A balanced rose fertilizer in early spring, repeated after the first flush to fuel the next.
  • Pruning: Prune it in late winter to an open, outward-facing framework, then deadhead through the season.
Bloom habit: Repeat (recurrent). White Knock Out blooms in repeated flushes from late spring until the first frost. Deadhead spent flowers to bring on the next wave.

Where to use White Knock Out in the garden

White Knock Out suits low hedges, mass plantings, foundation beds, and mixed borders. Combine it with ornamental grasses, perennials, and shrubs in low-maintenance landscape beds. For more ideas, see our guide to companion plants for roses.

Common problems and care

Bred for outstanding black-spot resistance, this rose rarely needs any spraying. Watch for the usual rose troubles — black spot, powdery mildew, and aphids — and head them off with good air flow, base watering, and a tidy autumn clean-up. See our full guide to rose diseases and pests for identification and treatment.

White Knock Out — frequently asked questions

How big does White Knock Out get?

White Knock Out typically grows about 3 to 4 feet tall and 3 to 4 feet wide, forming a rounded, bushy, self-supporting shrub. Its final size depends on your climate and how you prune it.

Is White Knock Out fragrant?

White Knock Out has a light, pleasant fragrance; it is grown more for its white color and habit than for perfume.

Does White Knock Out bloom more than once a season?

Yes. White Knock Out is a repeat-blooming rose that blooms in repeated flushes from late spring until the first frost, especially if it is deadheaded and fed through the summer.

What hardiness zones does White Knock Out grow in?

White Knock Out is hardy in USDA zones 5-11. That range describes the winter cold it can survive; gardeners colder than zone 5 should give it winter protection or grow it in a movable container.

Is White Knock Out easy to grow?

Bred for outstanding black-spot resistance, this rose rarely needs any spraying. Give White Knock Out full sun, well-drained soil, and the ordinary seasonal care any rose appreciates, and it is a straightforward rose to grow.

How and when should I prune White Knock Out?

Prune White Knock Out in late winter to an open, outward-facing framework, then deadhead through the season — see our step-by-step guide to pruning roses for the full method.

More knock out roses