How Tall Do Double Knock Out Roses Get?

Average Height

• Most Knock Out rose varieties grow 3 to 5 feet tall, and Double Knock Out roses are no exception. However, they tend to the shorter side, at 3 to 4 feet tall under most conditions. Several factors might lead them to stay smaller or outgrow their expected height.

Region

• The University of Illinois Extension describes Double Knock Out roses as a 3-foot-tall shrub, while the Texas A&M AgriLife Extension describes it as a 4-foot-tall shrub. The discrepancy lies in how the shrub performs in two very different growing regions. In warmer Southern temperatures with milder winters influenced by the waters of the Gulf of Mexico, roses in Texas have longer seasons to grow and suffer less damage from winter than those grown in the hard winters of Illinois.

Cultural Practices

• Knock Out roses that are trimmed every one to three years will favor a more compact form but may not get as tall. Knock Out roses left unpruned may be taller but more scraggly in appearance. Those grown in shadier spots may grow taller in search of sunlight but will not appear as healthy. Those grown in full sun will be fuller but usually favor putting on more leaves to growing taller. Fertilizer may make Double Knock Out roses grow faster but won't make them grow taller than their genetic predisposition allows.

Considerations

• Planting Double Knock Out roses with a mind to their mature size will ensure that they grow to the rounded shape and medium height they're prized for. Surrounding plants should be shorter than the roses, since roses prefer full sun. Knock Out roses perform well behind a border of shorter-growing artemisia, blue salvias or annual bedding flowers that won't crowd, hide or shade the Double Knock Out rose.