Prized for their easy care, disease resistance and extended blooming season, Knock Out roses (Rosa x 'Radrazz') are quite popular among gardeners. Propagating them is a simple process of taking a cutting and planting it to encourage rooting. Most gardeners enjoy a success rate of 50 to 75 percent, according to Texas A&M University Extension, when growing roses from cuttings, but a little rooting hormone can greatly improve your odds.
A Note on Legality
When searching online for advice on how to propagate Knock Out roses from cuttings, you'll find many people adamantly explaining that it is illegal to do so. In the past, that was true. The Knock Out rose variety was created by the Conrad-Pyle Company in Pennsylvania. It took 15 years to develop the cultivar, and the company filed a patent to protect its work.
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Because of this patent, it was illegal to propagate Knock Outs — even if you were doing so for your own personal garden use and not resale. Patents are only good for 20 years, however, and cannot be extended. Conrad-Pyle patented Knock Out roses in January 1999. The patent expired in January 2019, paving the way for gardeners who wish to grow cuttings of their Knock Out roses to legally do so.
How to Root a Knock Out Rose
Step 1: Take a Cutting
You can take a rose cutting any time, but most home gardeners fare best when doing so between November and February. For the best results, choose a stem that has blossomed recently. A stem that still has a withered flower or rose hips is an excellent candidate.
- Remove the spent flower or rose hips from your chosen stem, if applicable. Remove everything down to the first set of healthy leaves.
- Follow the stem down from these levels to the place where it branches off of the rest of the plant and cut it there. Make your cut at a 45-degree angle, using clean pruning shears. If you're not sure where you last used your pruning shears, wipe them down with a little alcohol to make sure they're not carrying any plant diseases. Your cutting should be about 6 to 8 inches long.
- Drop your rose cutting into some cool water if you're going to be in the garden for any length of time or if you need to transport your cuttings before preparing them. The sooner you can get them prepped and planted the more likely they are to root, but don't let them dry out in the meantime.
Step 2: Prepare and Plant the Cutting
Although not strictly necessary, you can increase your odds of rooting success by applying a little rooting hormone powder to your Knock Out rose cutting. Starting your cuttings indoors is also a good idea. You can plant your new cutting outside, but young plants need protection from the elements. It's much easier to control the growing conditions indoors.
- Remove any leaves from the bottom 2/3 of your cutting.
- Place a little rooting compound powder on a plate or countertop and roll the bottom of your stem in it.
- Plant the stem in a small pot full of fresh potting soil.
- Water your new plant gently but deeply.
- Cover the pot with a plastic ziplock bag to create your own miniature greenhouse. If necessary, place a wooden stake or cut section of coat hanger into the pot to keep the plastic bag from dropping down onto your new plant.
- Place the pot where it will receive ample but indirect sunlight.
Step 3: Growing and Transplanting Your New Roses
Most Knock Out rose cuttings start to grow roots in a month or two. These roots start out as tiny swellings that begin to develop into recognizable roots as spring arrives. During this time, it's important to keep your plants moist but never soggy. When you are ready to grow your roses outside, remember to slowly harden them off so they can adjust more readily to their new environment.
- Water your new plants often. You may need to check on them daily or every other day until you see how quickly they will dry out.
- Keep taking care of your plants indoors until early fall. The young plant's roots will be fully formed by April or May, but waiting until fall to plant them outdoors gives them a little more time to develop vigor and withstand transplanting.
- Choose a planting location in full sun where the soil drains well.
- Dig a hole twice the size of your Knock Out rose's root ball, place the plant in the hole and backfill. Water the plant thoroughly.
- Start your fertilizing routine next spring if desired. Fertilizing too soon may damage the plant's tender young roots.