How to Propagate Rhododendrons and Azaleas from Cuttings

Introduction to rhododendrons and azaleas

Although considered distinctly different by many horticulturalists and gardeners, botanists place both rhododendrons and azaleas in the genus Rhododendron. Linnaeus classified azaleas separately, as genus Azalea, but subsequent generations of botanists have decided that the two are closely enough related that they should share a classification. The primary visible difference between the two types of shrub is the number of stamens that each have. Azaleas generally have five stamens, while rhododendrons usually have ten1.

There are at least 850 species of Rhododendron worldwide1, 3, and the USDA lists 40 in the United States, including 11 native species2; Reiley, however lists 16 native species of azalea alone3. Rhododendron is in the Ericaceae family, which also includes heather, laurel, huckleberry, and blueberry. Here are a couple of species:

maximum

Rhododendron maximum, a native of eastern U.S. Photo by John Perkins.

Rhododendron catawbiense, another U.S. native. Photo by Sten Porse.

Rhododendron catawbiense, another U.S. native.
Photo by Sten Porse.

The oconee azalea, native to the southern U.S. Photo by Joey Williamson.

The oconee azalea, native to the southern U.S.
Photo by Joey Williamson.

Different varieties and species have different growing requirements. Some rhododendrons and azaleas that are native to the U.S. South or other warm regions have difficulty growing in cooler weather, and may be killed by very low temperatures. On the other hand, many species are very cold hardy and thrive in northern climates, but do not do well in hot southern climates3. I don’t think any of them would do very well down here in the islands, but just about anyplace you live in the United States you can find some rhododendrons or azaleas well-suited to your area. Native species may have some desirable characteristics that cannot be found in hybrid plants, but they can be difficult to find at nurseries and some native species, particularly azaleas, can be more difficult than hybrids to propagate by cuttings3.

You should consider the size that the plant will eventually achieve when choosing a location for it.  Some azalea varieties can grow to 10 feet high and some rhododendrons will reach 15 feet high when fully grown3, so make sure there is enough space for your particular variety to grow. Another consideration is the amount of sunlight the plants will receive. In the northeastern U.S., planting your rhododendrons or azaleas in full sun should be fine, but if you live in the southern or western states, or if the temperature remains above 90° F for an extended period like it does here in the islands, your plants may need some shade3.

Propagating Rhododendrons and Azaleas

There are as many ways to propagate rhododendrons and azaleas as there are ways to watch the sun set over the ocean. You can grow them from seed fairly easily, but the plants that grow may be quite different than the parent plant. For this reason, asexual propagation techniques are usually the preferred method of propagating these plants4. This can be done by several methods, including layering, grafting, budding, and with micropropagation techniques3,6 , but here we will just discuss propagation from cuttings. Ready?

Step-by-step propagation of rhododendrons and azaleas from cuttings

If you have a choice between varieties to propagate, the ones with smaller leaves tend to root more easily, but any varieties will root if you take enough care with them5.

Step 1. Get your tools and materials together. You’ll need:

  • A growing medium, roughly half peat moss and half perlite5. Commercial potting soil usually won’t have enough perlite in it for the soil to drain properly, and your cuttings could rot before they have a chance to grow. If you use the bagged stuff, you’re going to have to add more perlite anyway, so why not just mix your own?
  • A container, or some containers, depending on how many cuttings you’re working with. Any kind of box or flower pot-type thing will work, just make sure it’s very clean.
  • A very sharp blade. You can use a kitchen knife, shears, a utility knife, a razor blade—it doesn’t matter as long as it’s really sharp. And clean5.
  • Some kind of rooting hormone. If you haven’t used hormones before, the Dip ‘N Grow liquid is widely available and has a 1% concentration of the rooting hormone, which is just about right for your rhododendron or azalea cuttings6.

Step 2. Choose a young upright branch, one that’s light-colored and pliable5. Look for one without a bud, if you get a bud on your cutting, no problem, you can remove it later. Cut straight across the branch with your blade, about 3 to 6 inches from the tip. Remove the lowest leaves, and the bud, if it has one5. Your cuttings should look something like this:

Azalea Cuttings. Photo by Donald W. Hyatt

Azalea Cuttings.
Photo by Donald W. Hyatt

Step 3. Use your blade to strip about an inch of bark from the base of your cuttings. If your cuttings have large leaves (this will be the case with some rhododendrons), trim off the ends of the leaves. What you end up with should look something like this:

cuttings4-600

Rhododendron cuttings. Photo by Donald W. Hyatt

Step 4. Dip the tips of your cuttings into the rooting hormone, and stick the cuttings into your potting mix. You can put them pretty close to each other, because when their roots begin to grow you’ll be moving them out of this container anyway.

stekken_12

Rhododendron cuttings in potting mix. Photo by Tijs Huisman.

 

Step 5. Find a place for your cuttings to live for a while—this could be up to a few months. They’ll need to stay warm and have continual moisture. If you have a greenhouse with a misting system, you’re in luck. Otherwise, you can use a sunny window, but be careful, because window sills can get cold at times. If you’re not in a situation where you can mist them all the time (trust me, bruddah, you’re not), you may want to keep the cuttings covered with plastic–even a clear plastic bag over the container will work5.

If you followed all of these steps, your cuttings should grow roots within a couple of months. Then you can plant them and watch them go!

I hope you enjoyed this lesson–now go get right with Nature!! See you next time on Propagation Island!

 

References

1Andrews, Charles (2014). What is an azalea? Retrieved from http://azaleachapter.com/plant-info/plants/what-is-an-azalea

2United States Department of Agriculture Natural Resources Conservation Service. Plants Database. Retrieved from https://plants.usda.gov/java/

3Reiley, H. E. (2004). Success with Rhododendrons and Azaleas (Rev. ed.). Portland, OR: Timber Press.

4Clarke, J. H. (1982). Getting Started with Rhododendrons and Azaleas (Reprint ed.). Portland, OR: Timber Press.

5Dorsey, Frank (1994). Tips for Beginners: Success with Rooting Cuttings. American Rhododendron Society. Retrieved from http://www.rhododendron.org/v48n4p201.htm

6Hartmann, H. T., Kester, D. E., Davies Jr., F. T., Geneve, R. L. (2011). Rhododendron spp. Hartmann & Kester’s Plant Propagation Principles and Practices (8th ed.). Upper Saddle River, NJ: Pearson Education.

Cover photo courtesy of Reggae Marathon Limited.

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