Double Knock Out rose
image by H.B. Dean
The Double Knock Out rose is a popular choice for beginning and veteran gardeners alike. The double version of the original Knock Out grows 3 to 4 feet tall and 3 to 4 feet wide. The double flowers--available in pink, red, coral and yellow--bloom from spring until the first frost. Once established in the garden, the Double Knock Out rose is disease-resistant, drought-tolerant and requires little maintenance.
Preparing and Planting
Prepare the garden for Double Knock Out roses a month before planting. Like all roses, they need at least six hours of full sunlight daily. They thrive in rich, well-drained soil that has a pH of 5.8 to 6.8. Test the soil a month before planting and amend it with sulfur or lime if necessary. The University of California Extension has a chart explaining how to amend different types of soil.
Plant the rose after all threat of frost has passed. Dig a hole 2 feet deep and 2 feet wide, placing the soil on a tarp or in a wheelbarrow. Estimate the amount of soil removed and add equal amounts of mulch, peat moss and potting soil to create a planting mix. Fill the hole half full with the planting mix, add water to the top of the hole and mix with a shovel. The water/planting mix should be thick like melted ice cream.
Place the Double Knock Out rose in the middle of the water/planting mix. Hold it so the bud union--the swelling where the rose's roots and canes meet--is directly above the hole. Add more planting mix until the hole is filled and the mix is firm.
Spread a 2-inch layer of mulch under the rose bush. Build a dam with the mulch around the rose, about 1 foot away on all sides. This will hold in the water while the rose is settling into the garden. Cover the bud union with mulch until new growth appears, then gradually remove it.
Water the Double Knock Out rose about once a week, depending on rainfall. The rose needs an average of 1 inch of water per week. Do not spray the bush--direct the water toward the roots.
Feed the plant with a complete rose food. The method and frequency of application depends on the type of rose food.
Weed around the bush, using a tool to remove weeds by their roots. Lawn fabric placed under the mulch reduces the growth of weeds.
Prune the Double Knock Out rose in the spring. Cut it about 1/3 to 1/2 of the bush's height. Knock Out roses are self-cleaning, so there is no need to deadhead.