Watching the garden wake up is one of the most exciting parts of gardening. It is so much fun to anticipate the leaves returning and the flowers. This anticipation of flowers has inspired me to write a bit about one of my favorites: azaleas and rhododendrons. There is seemingly infinite information about rhododendrons, so I am mostly going to be focusing on a few different types, uses, and care of the plants in the genus. I’m going to start with the most confusing part of this blog, what is the difference between an azalea and a rhododendron?
The distinction between azaleas and rhododendrons had been around for a long time and they were originally classified into different genera. Then, scientists noticed they are not significantly different and lumped them into the same genus, Rhododendron, and about twenty years ago were split into sections of different subgenera. The way the azalea classifications were split shows that some azaleas are more closely related to true rhododendrons than they are to azaleas, which makes the concept of a “true azalea” very confusing. Some azaleas are able to be hybridized with true rhododendrons (not other azaleas), despite what most people would expect. I will sum up the differences with a quote from Michael A. Dirr’s Manual of Woody Landscape Plants: “There are no clear cut lines for distinguishing all azaleas from all rhododendrons.”
If you have ever looked for a different cultivar of rhododendron from what is offered locally, you might have noticed there is a wide range of colors and sizes of plants. Then, once you got excited about all of the options, you realized northern Indiana is too harsh for most of the colorful and exotic looking rhododendrons. Fortunately, breeders are starting to produce rhododendrons that are very cold hardy and give us the exceptional colors we crave for our gardens. Most of the hybrids are not developed nearby and cannot be found easily in local garden centers; they are either a far drive or a mail order away. In my opinion, it is worth the little bit of extra effort to get spectacular plants that will be a part of your landscape for years to come.
Speaking of liking the warmer weather, there is a tropical group of rhododendrons called Vireyas that cannot tolerate cold temperatures at all. They love warm weather so much, they can even be grown indoors as a houseplant. They tend to grow as epiphytes in a tree, the same way orchids can. They are a great alternative if winters are too cold for other rhododendrons. The biggest downside is the lack of a display. Vireyas flower sporadically instead of setting a full bloom all at once like most of our local plants.
Rhododendrons can make excellent landscaping plants and houseplants. But did you know there are some that are grown specifically for the Japanese art of bonsai? The two main hybrids used for bonsai are Kurume and Satsuki; they are both types of dwarf azaleas, which make them better for bonsai, since they already have smaller leaves and flowers. Rhododendrons have also been used as medicinal and recreational drugs in some parts of the world – although I would not suggest consumption of them, because all rhododendrons are poisonous! In Turkey, honey made from rhododendron nectar is known as “mad honey” and can cause hallucinations. The toxin responsible for all of these effects is called “grayanotoxin” and is in most plants in the family. Some have even higher concentrations than rhododendrons.
Like I said, there is seemingly infinite information about rhododendrons. I will probably write about more interesting facts about these amazing plants in the future, as there is so much to be said about one of the most exciting plants in the garden. Hopefully, everyone will get a chance to get into the gardens and see our rhododendrons. The earliest blooming azaleas are getting started now, as you can see in our photo. We hope you are able to come out to Wellfield and see our spring blooms!
Cody Hoff, Lead Horticulturist