According to the University of Florida website, the Knockout rose (or Rosa 'Radrazz' family) was created by rose breeder Bill Radler in 2000. The original Knock Out rose (as spelled by Radler) is a cross between a 'Carefree Beauty' and a 'Razzle Dazzle.' However, the species is now available in other varieties, as well. Knockout roses grow best in USDA hardiness zones 4 to 9 and can reach heights up to 3 feet with spreads ranging from 2 to 5 feet or more, if not pruned.
Select a location to plant the Knockout roses that provides well-draining soil and partial shade to full sun. Allow enough space for the mature height and width of the plant.
Cultivate the soil in the site to a depth equal to the Knockout rose's container and at least two times the width. Add organic matter to the soil to enrich it. Dig a hole in the center (as deep as the container) for planting the Knockout rose.
Carefully remove the Knockout rose from the container. Inspect the roots for damage, and remove any damaged sections found. Straighten out any entangled or root-bound roots.
Place the Knockout roses in the hole, spreading out the root system. Add or remove soil from the planting hole so it sits at the same height as in the container.
Back fill the hole partially full, and press gently to firm the soil. Finish filling the hole with soil and saturate with water to remove air pockets. Add more dirt after watering, if needed, to cover the root ball.
Cover the area around the Knockout roses with a 3-inch layer of mulch. Keep the mulch away from the stem. The mulch will keep the area weed-free and retain moisture longer in the soil.
Supply enough water weekly to the Knockout rose plant to maintain moist soil during the growing season. This will vary depending on rainfall amounts, soil conditions and your location. Check the soil to a depth of 2 inches and saturate with water when it is dry.