A Knockout Rose tree is an ideal landscape tree where the desirability of the classic rose form can be incorporated into a structural arrangement with the benefit of that of a common tree. The Knockout Rose tree is an upright tree which forms a tidy mound 3 to 4 feet high from the base and blooms from June until the first hard frost. Knockout Rose trees and Knockout Rose shrubs complement each other well when planted together.
Knockout Rose trees look best planted in groups of three or more and can be planted to form low rise hedges. They also make for good feature trees when planted alongside Double Knockout Roses. Last year alone, some 3 ½ million Knockout Rose trees (of which many were Double Knockout Roses) were sold making them a very popular choice amongst gardeners.
Seasonal information: They are upright shrubs that form a tidy mound 3 to 4 feet high and bloom from June to the first hard frost. In spring, trim any broken or dead branches. You can shape the Knockout rose at this time. In zones with cold, wet winters, give your Knockout rose winter protection by planting on the leeward side of buildings or walls. Or you can wrap snow fencing loosely around the rose and cover with straw.
Location: Select a well-drained site in full to partial sun. If you choose partial sun make sure your roses receive at least six hours of direct sun a day (afternoon shade is better than morning shade). If you have clay or sandy soil, work well-rotted manure or compost into the planting site.
Planting instructions: You should start by digging a hole twice as wide and twice as deep as the root ball. Mix the manure or compost with the soil you have removed. Back fill the soil until you have a hole the same size or slightly larger than the container the rose is in. Plant the rose at the same depth as it is in the container. Space plants three feet apart.
Watering: Keep Knockout Roses moist at all times. Water around the roots rather than overhead.
Fertilization: Fertilize with an organic rose fertilizer once a month. Use organic fertilizer rather than synthetic fertilizers. Synthetic fertilizers can promote weak growth, and your rose will have more foliage and less flowers. Even though Double Knockout roses are disease-resistant, they still need adequate air circulation, created by properly spacing plants.
Pests and Disease: Knockout roses are resistant to rust, black spot and powdery mildew.
Pruning: Avoid pruning the Knockout roses at all in the first 2 to 3 years. Sterilize your sharp pruning shears with hot water or alcohol. This guarantees a cleaner, healthier cut. Always prune at an angle and not straight across. Activate the Knockout into growth and blooming by pruning it back a little in the spring after the last hard freeze. Keep the rose under control or if you want it smaller than it’s 3-feet wide by 4-inches tall size by pruning it back in the late summer or early fall. Remove dead or old canes at any time. Also cut very thin canes that might be coming up from the ground. Prune your mature plants by using the 1/3 rule each year in the spring. Remove 1/3 of the oldest canes and any stems that are damaged, diseased or dead.