Many species of woody trees and shrubs fall within the Rhododendron genus, including the tree Rhododendron arboretum, dwarf azalea (Rhododendron Atlanticum), and American Rhodendron (Rhododendron sempervirens) (Rhododendron maximum). Rhododendrons can be grown from seed, but cuttings can also be used to grow new rhododendron plants. To guarantee that your new rhododendron has the same flower color and other characteristics as the plant from which you took a cutting, or if you don’t have access to seeds, rooting a cutting is an excellent option. One to two days before cutting the rhododendron, water the plant to ensure that it is sufficiently hydrated. If there has been a lot of rain recently, you may not need to do this.
Mix 1 part bleach to 10 parts water to create a sanitizing solution. In addition to sterilizing the tools and containers you use, this solution will also be used during the actual cutting process.
Your sanitizing solution can be used to clean the interior of a plastic pot or another container. Prepare a moist yet crumbly rooting substrate by mixing equal parts peat moss and perlite with warm water, then add it to the sanitized container.
When taking cuttings, look for branches that are growing straight up and, if possible, have a terminal bud at the end of them. Remove the flower bud first if you can’t take a terminal bud cutting. Branches near the rhododendron’s crown or those that have turned brown are less likely to take root and should be avoided.
Take a 2 1/2 to 3 inch long cutting with your pruning shears after dipping them in the sanitizing solution. Take multiple cuttings in order to increase your chances of success.
Your cutting should only have about four to six leaves left after you’ve removed the rest. Reduce the remaining leaves by a third to a half. Remove all branches and needles from the bottom 1 1/2 inches of the cutting if the rhododendron variety from which you took a cutting has needles rather than leaves.
The bottom of the cutting should have two 1-inch-long slivers cut out of it to create wounds that will encourage root growth. Cuts on opposite sides of the cutting should only be deep enough to reveal the cutting’s inner wood.
After two to three seconds in the sanitizing solution, remove the cutting and let it drain on a sheet of paper. Individually sanitize each cutting if you are preparing multiples.
For hardwoods, use a rooting hormone powder that is specifically designed for this purpose. A thin layer of powder should adhere to the cutting and cover the wounds you’ve created.
Before placing your sanitized pot in your rooting substrate, make an opening and insert the cutting. Rooting hormone may fall off the cutting if you don’t drill a hole before placing the cutting. After all of the cuttings have been placed, fill the pot with water and place a clear plastic bag over the top to keep them moist. Wrap a rubber band around the pot’s edges to keep out any moisture.
The pot should be placed in an area with good light but not direct sunlight. The soil should be kept at around 70 degrees Fahrenheit.
Allow the cuttings to grow roots for two to four months. To prevent the spread of mold or disease to other cuttings, remove any that show signs of death or are beginning to mold. The cuttings can be transplanted to a pot or outdoor location for further growth once they begin to root, which you can check by gently moving the soil around them after two months.
Selection: Select smaller cuttings that do not have any buds on them as opposed to larger ones.
When taking root cuttings from my plants, I prefer to take the smaller shoots rather than the larger, more established ones. I look for items that don’t have flower buds on the backside of the plant or in shady spots. Since they don’t require as many roots as larger cuttings, smaller cuttings seem to root more easily for me. Aside from that, I’d rather not remove any twigs or branches that might bloom in the springtime. I remove any flower buds from cuttings so that the energy spent on flowering can be used to help the cutting’s root.
Prepare by snipping off the larger leaves.
Because Rhododendrons have shallow roots, cuttings need not be long. I use 1- to 2-inch-long short cuttings. To make them easier to handle, I also trim the ends of large leaves. Additional cuttings can be obtained by cutting long shoots into several sections. For varieties that are hard to come by, leaf-bud cuttings may be an option. An unbranched leaf bud cutting has a woody stem and a new growth bud. Rooting leaf-bud cuttings can be done the same way as normal cuttings, but it is important to keep the bud above ground when inserting the cutting because if it rots, the new growth will not emerge.
A small piece of bark from each side of the wound serves as a wounding agent.
New roots will grow from callus tissue that forms at the cambium layer of the cut stem as the cutting heals. I removed a thin sliver of bark from the bottom of the cutting on both sides in order to increase the surface area available for callus development. In order to avoid damaging the remaining bark, I use a sharp knife. This ensures that the new callus tissue grows in a healthy environment.
Cuttings should be soaked for five minutes in a 10% Clorox solution to sterilize them.
After removing the leaves and stems, I sterilize my cuttings to reduce the risk of insects and disease. To make a sterilizing solution, I combine 1/2 cup Clorox with 5 cups of water. In order to get rid of most bugs and mold spores on the cuttings, I soak them in the solution for five minutes. Afterward, I thoroughly rinse and shake the cuttings to remove any remaining water. Sterilization reduces the risk of contamination because the cuttings will be stored in plastic bags for months at a time.
Dip cuttings for 5 seconds in Dip ‘N Grow to activate hormones.
Most rhododendrons need a little help to get their roots going. Dip ‘N Grow, a liquid rooting concentrate, is what I use. I dilute rhododendron cuttings in a 1:15 ratio of the hormone to water for those that are difficult to root. A 1 to 10 dilution works well for azaleas. I remove the cutting ends after 5 seconds of immersion in the solution.
Insert the cuttings and place them in a clear plastic bag for potting up.
Peatmoss, grit, and perlite form a porous medium in which I plant the cuttings. In order to prevent rot, the medium must be damp but not soggy. Mini-greenhouses are created by placing a clear plastic bag over each pot and keeping the lights on for 18 hours each day. For months, cuttings should not need any water or attention. Until new growth appears the following year, I keep them under light and then transplant. Some varieties can root in two to three months, while others can take up to a year to establish.
